start, reverse guard, cli-frontend for server and client

2026-01-01 18:54:36 +03:00
commit 5fbb32d243
30 changed files with 4700 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -0,0 +1,4 @@
+/.cargo
+/.github
+/prompt.md
+/target
--- a/Cargo.lock
+++ b/Cargo.lock
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -0,0 +1,52 @@
+[workspace]
+resolver = "2"
+members = ["ostp", "oncp", "osn", "osds", "ostp-server", "ostp-client", "ostp-guard"]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2024"
+authors = ["Ospab Team"]
+license = "Proprietary"
+
+# ============================================================================
+# HARDENED RELEASE PROFILE - Anti-Reverse Engineering
+# ============================================================================
+[profile.release]
+lto = true                    # Link-Time Optimization - merges all code, removes boundaries
+codegen-units = 1             # Single codegen unit - better optimization, harder to analyze
+panic = "abort"               # No unwinding info - smaller binary, no stack traces
+strip = "symbols"             # Remove ALL symbols - no function names in binary
+opt-level = 3                 # Maximum optimization
+debug = false                 # No debug info
+debug-assertions = false      # No debug assertions
+overflow-checks = false       # No overflow checks (performance + less obvious control flow)
+incremental = false           # Reproducible builds
+
+# Distribution build - even more aggressive
+[profile.dist]
+inherits = "release"
+lto = "fat"                   # Full LTO across all crates
+strip = "debuginfo"           # Alternative stripping
+
+[workspace.dependencies]
+tokio = { version = "1.40", features = ["full"] }
+ring = "0.17"
+chacha20poly1305 = "0.10"
+x25519-dalek = { version = "2.0", features = ["static_secrets"] }
+bytes = "1.7"
+rusqlite = { version = "0.32", features = ["bundled"] }
+anyhow = "1.0"
+thiserror = "2.0"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+uuid = { version = "1.10", features = ["v4", "serde"] }
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+hmac = "0.12"
+sha2 = "0.10"
+rand = "0.8"
+chrono = { version = "0.4", features = ["serde"] }
+clap = { version = "4.5", features = ["derive", "env"] }
+hex = "0.4"
+dialoguer = "0.11"
+console = "0.15"
--- a/oncp/Cargo.toml
+++ b/oncp/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "oncp"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+tokio.workspace = true
+rusqlite.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+uuid.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+chrono.workspace = true
+ostp = { path = "../ostp" }
--- a/oncp/src/billing.rs
+++ b/oncp/src/billing.rs
@@ -0,0 +1,163 @@
+//! User billing and quota management
+
+use chrono::{DateTime, Utc};
+use std::sync::Mutex;
+use thiserror::Error;
+use uuid::Uuid;
+
+#[derive(Error, Debug)]
+pub enum BillingError {
+    #[error("user not found: {0}")]
+    UserNotFound(Uuid),
+    #[error("subscription expired")]
+    Expired,
+    #[error("bandwidth quota exceeded")]
+    QuotaExceeded,
+    #[error("database error: {0}")]
+    Database(#[from] rusqlite::Error),
+    #[error("lock error")]
+    LockError,
+}
+
+/// User account with billing info
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct User {
+    pub uuid: Uuid,
+    pub bandwidth_quota: u64,      // bytes allowed
+    pub bandwidth_used: u64,       // bytes used
+    pub expires_at: DateTime<Utc>, // subscription expiry
+    pub active: bool,
+}
+
+impl User {
+    pub fn new(quota_gb: u64, valid_days: i64) -> Self {
+        Self {
+            uuid: Uuid::new_v4(),
+            bandwidth_quota: quota_gb * 1024 * 1024 * 1024,
+            bandwidth_used: 0,
+            expires_at: Utc::now() + chrono::Duration::days(valid_days),
+            active: true,
+        }
+    }
+
+    pub fn is_valid(&self) -> bool {
+        self.active && Utc::now() < self.expires_at && self.bandwidth_used < self.bandwidth_quota
+    }
+
+    pub fn remaining_quota(&self) -> u64 {
+        self.bandwidth_quota.saturating_sub(self.bandwidth_used)
+    }
+}
+
+/// Abstract user registry trait
+pub trait UserRegistry: Send + Sync {
+    fn get_user(&self, uuid: &Uuid) -> Result<Option<User>, BillingError>;
+    fn create_user(&self, user: &User) -> Result<(), BillingError>;
+    fn update_bandwidth(&self, uuid: &Uuid, bytes: u64) -> Result<(), BillingError>;
+    fn validate_user(&self, uuid: &Uuid) -> Result<bool, BillingError>;
+}
+
+/// SQLite implementation (thread-safe via Mutex)
+pub struct SqliteRegistry {
+    conn: Mutex<rusqlite::Connection>,
+}
+
+impl SqliteRegistry {
+    pub fn new(path: &str) -> Result<Self, BillingError> {
+        let conn = rusqlite::Connection::open(path)?;
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS users (
+                uuid TEXT PRIMARY KEY,
+                bandwidth_quota INTEGER NOT NULL,
+                bandwidth_used INTEGER NOT NULL DEFAULT 0,
+                expires_at TEXT NOT NULL,
+                active INTEGER NOT NULL DEFAULT 1
+            )",
+            [],
+        )?;
+        Ok(Self { conn: Mutex::new(conn) })
+    }
+
+    pub fn in_memory() -> Result<Self, BillingError> {
+        Self::new(":memory:")
+    }
+}
+
+impl UserRegistry for SqliteRegistry {
+    fn get_user(&self, uuid: &Uuid) -> Result<Option<User>, BillingError> {
+        let conn = self.conn.lock().map_err(|_| BillingError::LockError)?;
+        let mut stmt = conn
+            .prepare("SELECT uuid, bandwidth_quota, bandwidth_used, expires_at, active FROM users WHERE uuid = ?")?;
+
+        let mut rows = stmt.query([uuid.to_string()])?;
+
+        if let Some(row) = rows.next()? {
+            let uuid_str: String = row.get(0)?;
+            let expires_str: String = row.get(3)?;
+            Ok(Some(User {
+                uuid: Uuid::parse_str(&uuid_str).unwrap(),
+                bandwidth_quota: row.get(1)?,
+                bandwidth_used: row.get(2)?,
+                expires_at: DateTime::parse_from_rfc3339(&expires_str)
+                    .unwrap()
+                    .with_timezone(&Utc),
+                active: row.get::<_, i32>(4)? == 1,
+            }))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn create_user(&self, user: &User) -> Result<(), BillingError> {
+        let conn = self.conn.lock().map_err(|_| BillingError::LockError)?;
+        conn.execute(
+            "INSERT INTO users (uuid, bandwidth_quota, bandwidth_used, expires_at, active) VALUES (?, ?, ?, ?, ?)",
+            (
+                user.uuid.to_string(),
+                user.bandwidth_quota,
+                user.bandwidth_used,
+                user.expires_at.to_rfc3339(),
+                if user.active { 1 } else { 0 },
+            ),
+        )?;
+        Ok(())
+    }
+
+    fn update_bandwidth(&self, uuid: &Uuid, bytes: u64) -> Result<(), BillingError> {
+        let conn = self.conn.lock().map_err(|_| BillingError::LockError)?;
+        let updated = conn.execute(
+            "UPDATE users SET bandwidth_used = bandwidth_used + ? WHERE uuid = ?",
+            (bytes, uuid.to_string()),
+        )?;
+        if updated == 0 {
+            return Err(BillingError::UserNotFound(*uuid));
+        }
+        Ok(())
+    }
+
+    fn validate_user(&self, uuid: &Uuid) -> Result<bool, BillingError> {
+        match self.get_user(uuid)? {
+            Some(user) => Ok(user.is_valid()),
+            None => Ok(false),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_user_lifecycle() {
+        let reg = SqliteRegistry::in_memory().unwrap();
+        let user = User::new(100, 30); // 100GB, 30 days
+        let uuid = user.uuid;
+
+        reg.create_user(&user).unwrap();
+        assert!(reg.validate_user(&uuid).unwrap());
+
+        reg.update_bandwidth(&uuid, 1024).unwrap();
+        let updated = reg.get_user(&uuid).unwrap().unwrap();
+        assert_eq!(updated.bandwidth_used, 1024);
+    }
+}
--- a/oncp/src/lib.rs
+++ b/oncp/src/lib.rs
@@ -0,0 +1,5 @@
+pub mod billing;
+pub mod session;
+
+pub use billing::{BillingError, SqliteRegistry, User, UserRegistry};
+pub use session::{Session, SessionManager};
--- a/oncp/src/session.rs
+++ b/oncp/src/session.rs
@@ -0,0 +1,109 @@
+//! Session management and heartbeat
+
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::RwLock;
+use uuid::Uuid;
+
+/// Session state
+#[derive(Debug, Clone)]
+pub struct Session {
+    pub user_id: Uuid,
+    pub session_id: Uuid,
+    pub created_at: Instant,
+    pub last_heartbeat: Instant,
+    pub bytes_tx: u64,
+    pub bytes_rx: u64,
+    pub sni: String,
+}
+
+impl Session {
+    pub fn new(user_id: Uuid, sni: String) -> Self {
+        let now = Instant::now();
+        Self {
+            user_id,
+            session_id: Uuid::new_v4(),
+            created_at: now,
+            last_heartbeat: now,
+            bytes_tx: 0,
+            bytes_rx: 0,
+            sni,
+        }
+    }
+
+    pub fn heartbeat(&mut self) {
+        self.last_heartbeat = Instant::now();
+    }
+
+    pub fn is_alive(&self, timeout: Duration) -> bool {
+        self.last_heartbeat.elapsed() < timeout
+    }
+}
+
+/// Session manager
+pub struct SessionManager {
+    sessions: Arc<RwLock<HashMap<Uuid, Session>>>,
+    heartbeat_timeout: Duration,
+}
+
+impl SessionManager {
+    pub fn new(heartbeat_timeout_secs: u64) -> Self {
+        Self {
+            sessions: Arc::new(RwLock::new(HashMap::new())),
+            heartbeat_timeout: Duration::from_secs(heartbeat_timeout_secs),
+        }
+    }
+
+    pub async fn create_session(&self, user_id: Uuid, sni: String) -> Uuid {
+        let session = Session::new(user_id, sni);
+        let session_id = session.session_id;
+        self.sessions.write().await.insert(session_id, session);
+        session_id
+    }
+
+    pub async fn heartbeat(&self, session_id: &Uuid) -> bool {
+        if let Some(session) = self.sessions.write().await.get_mut(session_id) {
+            session.heartbeat();
+            true
+        } else {
+            false
+        }
+    }
+
+    pub async fn get_session(&self, session_id: &Uuid) -> Option<Session> {
+        self.sessions.read().await.get(session_id).cloned()
+    }
+
+    pub async fn remove_session(&self, session_id: &Uuid) -> Option<Session> {
+        self.sessions.write().await.remove(session_id)
+    }
+
+    pub async fn cleanup_stale(&self) -> Vec<Uuid> {
+        let mut sessions = self.sessions.write().await;
+        let timeout = self.heartbeat_timeout;
+        let stale: Vec<Uuid> = sessions
+            .iter()
+            .filter(|(_, s)| !s.is_alive(timeout))
+            .map(|(id, _)| *id)
+            .collect();
+
+        for id in &stale {
+            sessions.remove(id);
+        }
+        stale
+    }
+
+    pub async fn update_traffic(&self, session_id: &Uuid, tx: u64, rx: u64) {
+        if let Some(session) = self.sessions.write().await.get_mut(session_id) {
+            session.bytes_tx += tx;
+            session.bytes_rx += rx;
+        }
+    }
+}
+
+impl Default for SessionManager {
+    fn default() -> Self {
+        Self::new(60)
+    }
+}
--- a/osds/Cargo.toml
+++ b/osds/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "osds"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+tokio.workspace = true
+bytes.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+rand.workspace = true
+ostp = { path = "../ostp" }
--- a/osds/src/dns.rs
+++ b/osds/src/dns.rs
@@ -0,0 +1,139 @@
+//! Stealth DNS resolver - DoH/DoT with anti-hijacking
+
+use bytes::{BufMut, BytesMut};
+use std::net::SocketAddr;
+use thiserror::Error;
+use tokio::net::UdpSocket;
+
+#[derive(Error, Debug)]
+pub enum DnsError {
+    #[error("io error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("invalid query")]
+    InvalidQuery,
+    #[error("upstream timeout")]
+    Timeout,
+    #[error("hijacking detected")]
+    HijackDetected,
+}
+
+/// DNS query types
+#[derive(Debug, Clone, Copy)]
+pub enum QueryType {
+    A = 1,
+    AAAA = 28,
+    CNAME = 5,
+    TXT = 16,
+}
+
+/// Minimal DNS query builder
+pub fn build_dns_query(domain: &str, qtype: QueryType) -> BytesMut {
+    let mut buf = BytesMut::with_capacity(512);
+
+    // Transaction ID (random)
+    let txid: u16 = rand::random();
+    buf.put_u16(txid);
+
+    // Flags: standard query, recursion desired
+    buf.put_u16(0x0100);
+
+    // Questions: 1, Answers: 0, Authority: 0, Additional: 0
+    buf.put_u16(1);
+    buf.put_u16(0);
+    buf.put_u16(0);
+    buf.put_u16(0);
+
+    // QNAME
+    for label in domain.split('.') {
+        buf.put_u8(label.len() as u8);
+        buf.put_slice(label.as_bytes());
+    }
+    buf.put_u8(0); // null terminator
+
+    // QTYPE and QCLASS (IN)
+    buf.put_u16(qtype as u16);
+    buf.put_u16(1); // IN class
+
+    buf
+}
+
+/// DNS forwarder that tunnels queries through OSTP
+pub struct StealthDnsForwarder {
+    listen_addr: SocketAddr,
+    /// Upstream resolver (will be tunneled through OSTP)
+    upstream: SocketAddr,
+}
+
+impl StealthDnsForwarder {
+    pub fn new(listen: SocketAddr, upstream: SocketAddr) -> Self {
+        Self {
+            listen_addr: listen,
+            upstream,
+        }
+    }
+
+    /// Start DNS listener (intercepts local queries)
+    pub async fn run(&self) -> Result<(), DnsError> {
+        let socket = UdpSocket::bind(self.listen_addr).await?;
+        tracing::info!("DNS forwarder listening on {}", self.listen_addr);
+
+        let mut buf = [0u8; 512];
+        loop {
+            let (len, src) = socket.recv_from(&mut buf).await?;
+            let query = &buf[..len];
+
+            // TODO: Encrypt and forward through OSTP tunnel instead of direct
+            // For now, direct forward (to be replaced with tunnel)
+            match self.forward_query(query).await {
+                Ok(response) => {
+                    let _ = socket.send_to(&response, src).await;
+                }
+                Err(e) => {
+                    tracing::warn!("DNS forward failed: {}", e);
+                }
+            }
+        }
+    }
+
+    async fn forward_query(&self, query: &[u8]) -> Result<Vec<u8>, DnsError> {
+        let socket = UdpSocket::bind("0.0.0.0:0").await?;
+        socket.send_to(query, self.upstream).await?;
+
+        let mut response = vec![0u8; 512];
+        let timeout = tokio::time::timeout(
+            std::time::Duration::from_secs(5),
+            socket.recv_from(&mut response),
+        )
+        .await;
+
+        match timeout {
+            Ok(Ok((len, _))) => {
+                response.truncate(len);
+                Ok(response)
+            }
+            Ok(Err(e)) => Err(DnsError::Io(e)),
+            Err(_) => Err(DnsError::Timeout),
+        }
+    }
+}
+
+/// Anti-hijacking: verify response matches known-good resolver fingerprint
+pub fn detect_hijack(response: &[u8], expected_patterns: &[[u8; 4]]) -> bool {
+    // Check if response contains known hijack IPs (ISP redirect pages, etc.)
+    // Simplified: check for common hijack patterns
+    if response.len() < 12 {
+        return true; // Suspicious short response
+    }
+
+    // Check for NXDOMAIN being rewritten (common hijack)
+    let rcode = response[3] & 0x0F;
+    if rcode == 0 {
+        // NOERROR - check if IP is in known hijack list
+        for pattern in expected_patterns {
+            if response.windows(4).any(|w| w == pattern) {
+                return true;
+            }
+        }
+    }
+    false
+}
--- a/osds/src/lib.rs
+++ b/osds/src/lib.rs
@@ -0,0 +1,3 @@
+pub mod dns;
+
+pub use dns::{build_dns_query, detect_hijack, DnsError, QueryType, StealthDnsForwarder};
--- a/osn/Cargo.toml
+++ b/osn/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "osn"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+tokio.workspace = true
+bytes.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+async-trait = "0.1"
--- a/osn/src/lib.rs
+++ b/osn/src/lib.rs
@@ -0,0 +1,3 @@
+pub mod tun;
+
+pub use tun::{DummyTun, Router, TunConfig, TunDevice, TunError};
--- a/osn/src/tun.rs
+++ b/osn/src/tun.rs
@@ -0,0 +1,95 @@
+//! Virtual network interface (TUN/TAP) abstraction
+
+use bytes::Bytes;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum TunError {
+    #[error("failed to create interface: {0}")]
+    Create(String),
+    #[error("io error: {0}")]
+    Io(#[from] std::io::Error),
+    #[error("interface not ready")]
+    NotReady,
+}
+
+/// TUN device configuration
+#[derive(Debug, Clone)]
+pub struct TunConfig {
+    pub name: String,
+    pub address: [u8; 4],
+    pub netmask: [u8; 4],
+    pub mtu: u16,
+}
+
+impl Default for TunConfig {
+    fn default() -> Self {
+        Self {
+            name: "ostp0".into(),
+            address: [10, 0, 0, 1],
+            netmask: [255, 255, 255, 0],
+            mtu: 1400,
+        }
+    }
+}
+
+/// Abstract TUN device trait
+#[async_trait::async_trait]
+pub trait TunDevice: Send + Sync {
+    async fn read(&self) -> Result<Bytes, TunError>;
+    async fn write(&self, data: &[u8]) -> Result<usize, TunError>;
+    fn mtu(&self) -> u16;
+}
+
+/// Placeholder TUN implementation (platform-specific impl needed)
+pub struct DummyTun {
+    config: TunConfig,
+}
+
+impl DummyTun {
+    pub fn new(config: TunConfig) -> Self {
+        Self { config }
+    }
+}
+
+#[async_trait::async_trait]
+impl TunDevice for DummyTun {
+    async fn read(&self) -> Result<Bytes, TunError> {
+        // Platform-specific: use wintun on Windows, tun-tap on Linux
+        Err(TunError::NotReady)
+    }
+
+    async fn write(&self, _data: &[u8]) -> Result<usize, TunError> {
+        Err(TunError::NotReady)
+    }
+
+    fn mtu(&self) -> u16 {
+        self.config.mtu
+    }
+}
+
+/// IP packet routing helper
+pub struct Router {
+    default_gateway: [u8; 4],
+}
+
+impl Router {
+    pub fn new(gateway: [u8; 4]) -> Self {
+        Self {
+            default_gateway: gateway,
+        }
+    }
+
+    /// Check if IP should be tunneled
+    pub fn should_tunnel(&self, dest_ip: &[u8; 4]) -> bool {
+        // Don't tunnel local/private ranges by default
+        !matches!(
+            dest_ip,
+            [10, ..] | [127, ..] | [192, 168, ..] | [172, 16..=31, ..]
+        )
+    }
+
+    pub fn gateway(&self) -> [u8; 4] {
+        self.default_gateway
+    }
+}
--- a/ostp-client/Cargo.toml
+++ b/ostp-client/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+name = "ostp-client"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Stealth VPN Client"
+
+[[bin]]
+name = "ostp-client"
+path = "src/main.rs"
+
+[dependencies]
+ostp = { path = "../ostp" }
+ostp-guard = { path = "../ostp-guard" }
+tokio.workspace = true
+anyhow.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+clap.workspace = true
+hex.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+dialoguer.workspace = true
+console.workspace = true
+
+[target.'cfg(windows)'.dependencies]
+# Windows-specific deps will go here (wintun, etc.)
--- a/ostp-client/src/main.rs
+++ b/ostp-client/src/main.rs
@@ -0,0 +1,420 @@
+//! OSTP Client CLI - Stealth VPN Client for Windows
+//!
+//! Usage:
+//!   ostp-client connect --server 1.2.3.4:8443 --psk <hex-key>
+//!   ostp-client --config %APPDATA%/ostp/client.json
+
+use anyhow::{Context, Result};
+use clap::{Parser, Subcommand};
+use console::{style, Emoji};
+use dialoguer::{Confirm, Input, Select};
+use ostp::{ClientConfig, OstpClient};
+use ostp_guard::error_codes;
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use tracing_subscriber::{fmt, prelude::*, EnvFilter};
+
+static ROCKET: Emoji<'_, '_> = Emoji("🚀 ", "");
+static LOCK: Emoji<'_, '_> = Emoji("🔒 ", "");
+static CHECK: Emoji<'_, '_> = Emoji("✅ ", "[OK] ");
+static WARN: Emoji<'_, '_> = Emoji("⚠️  ", "[!] ");
+static GLOBE: Emoji<'_, '_> = Emoji("🌍 ", "");
+
+#[derive(Parser)]
+#[command(name = "ostp-client")]
+#[command(author = "Ospab Team")]
+#[command(version)]
+#[command(about = "OSTP Stealth VPN Client", long_about = None)]
+struct Cli {
+    #[command(subcommand)]
+    command: Option<Commands>,
+
+    /// Path to config file (JSON)
+    #[arg(short, long)]
+    config: Option<PathBuf>,
+
+    /// Log level (trace, debug, info, warn, error)
+    #[arg(long, default_value = "info")]
+    log_level: String,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    /// Connect to an OSTP server
+    Connect {
+        /// Server address (e.g., vpn.example.com:8443)
+        #[arg(short, long)]
+        server: SocketAddr,
+
+        /// Pre-shared key in hex format
+        #[arg(short, long, env = "OSTP_PSK")]
+        psk: String,
+
+        /// Country code for SNI mimicry (RU, US, DE, NO, CN)
+        #[arg(short = 'c', long, default_value = "US")]
+        country: String,
+    },
+    /// Interactive setup wizard
+    Setup,
+    /// Test connection to server
+    Test {
+        /// Server address
+        #[arg(short, long)]
+        server: SocketAddr,
+
+        /// Pre-shared key in hex format
+        #[arg(short, long)]
+        psk: String,
+    },
+    /// Show saved profiles
+    Profiles,
+}
+
+#[derive(serde::Deserialize, serde::Serialize, Clone)]
+#[allow(dead_code)]
+struct ClientConfigFile {
+    server: String,
+    psk: String,
+    country: Option<String>,
+    log_level: Option<String>,
+}
+
+#[derive(serde::Deserialize, serde::Serialize, Default)]
+struct ProfilesFile {
+    profiles: Vec<Profile>,
+    default_profile: Option<String>,
+}
+
+#[derive(serde::Deserialize, serde::Serialize, Clone)]
+struct Profile {
+    name: String,
+    server: String,
+    psk: String,
+    country: String,
+}
+
+fn setup_logging(level: &str) {
+    let filter = EnvFilter::try_from_default_env()
+        .unwrap_or_else(|_| EnvFilter::new(level));
+
+    tracing_subscriber::registry()
+        .with(fmt::layer()
+            .with_target(false)
+            .with_thread_ids(false)
+            .without_time())
+        .with(filter)
+        .init();
+}
+
+fn parse_psk(hex_str: &str) -> Result<[u8; 32]> {
+    let bytes = hex::decode(hex_str.trim())
+        .context("Invalid hex string for PSK")?;
+    
+    if bytes.len() != 32 {
+        anyhow::bail!("PSK must be exactly 32 bytes (64 hex characters), got {}", bytes.len());
+    }
+    
+    let mut psk = [0u8; 32];
+    psk.copy_from_slice(&bytes);
+    Ok(psk)
+}
+
+fn get_config_dir() -> PathBuf {
+    #[cfg(windows)]
+    {
+        std::env::var("APPDATA")
+            .map(PathBuf::from)
+            .unwrap_or_else(|_| PathBuf::from("."))
+            .join("ostp")
+    }
+    #[cfg(not(windows))]
+    {
+        std::env::var("HOME")
+            .map(PathBuf::from)
+            .unwrap_or_else(|_| PathBuf::from("."))
+            .join(".config")
+            .join("ostp")
+    }
+}
+
+fn print_banner() {
+    println!();
+    println!("{}", style("╔════════════════════════════════════════════════════════╗").cyan());
+    println!("{}", style("║           OSTP Stealth VPN Client                      ║").cyan());
+    println!("{}", style("║                                                        ║").cyan());
+    println!("{}", style("║   Invisible by Default • Contextual Mimicry            ║").cyan());
+    println!("{}", style("╚════════════════════════════════════════════════════════╝").cyan());
+    println!();
+}
+
+async fn interactive_setup() -> Result<()> {
+    print_banner();
+    
+    println!("{}Welcome to OSTP Client Setup Wizard\n", ROCKET);
+
+    let profile_name: String = Input::new()
+        .with_prompt("Profile name")
+        .default("default".into())
+        .interact_text()?;
+
+    let server: String = Input::new()
+        .with_prompt("Server address (host:port)")
+        .interact_text()?;
+
+    let psk: String = Input::new()
+        .with_prompt("Pre-shared key (hex)")
+        .interact_text()?;
+
+    // Validate PSK
+    parse_psk(&psk)?;
+
+    let countries = vec!["US", "RU", "DE", "NO", "CN", "Custom"];
+    let country_idx = Select::new()
+        .with_prompt("Select country for SNI mimicry")
+        .items(&countries)
+        .default(0)
+        .interact()?;
+
+    let country = if country_idx == countries.len() - 1 {
+        Input::new()
+            .with_prompt("Enter custom country code")
+            .interact_text()?
+    } else {
+        countries[country_idx].to_string()
+    };
+
+    let profile = Profile {
+        name: profile_name.clone(),
+        server,
+        psk,
+        country,
+    };
+
+    // Save profile
+    let config_dir = get_config_dir();
+    std::fs::create_dir_all(&config_dir)?;
+    
+    let profiles_path = config_dir.join("profiles.json");
+    let mut profiles: ProfilesFile = if profiles_path.exists() {
+        let content = std::fs::read_to_string(&profiles_path)?;
+        serde_json::from_str(&content).unwrap_or_default()
+    } else {
+        ProfilesFile::default()
+    };
+
+    // Remove existing profile with same name
+    profiles.profiles.retain(|p| p.name != profile_name);
+    profiles.profiles.push(profile);
+    
+    if profiles.default_profile.is_none() {
+        profiles.default_profile = Some(profile_name.clone());
+    }
+
+    std::fs::write(&profiles_path, serde_json::to_string_pretty(&profiles)?)?;
+
+    println!();
+    println!("{}Profile '{}' saved to {:?}", CHECK, style(&profile_name).green(), profiles_path);
+
+    if Confirm::new()
+        .with_prompt("Connect now?")
+        .default(true)
+        .interact()?
+    {
+        let profile = profiles.profiles.iter().find(|p| p.name == profile_name).unwrap();
+        connect_to_server(&profile.server, &profile.psk, &profile.country).await?;
+    }
+
+    Ok(())
+}
+
+async fn connect_to_server(server: &str, psk_hex: &str, country: &str) -> Result<()> {
+    let server_addr: SocketAddr = server.parse()
+        .context("Invalid server address")?;
+    let psk = parse_psk(psk_hex)?;
+
+    println!();
+    println!("{}Connecting to {}", GLOBE, style(server).yellow());
+    println!("{}Country mimicry: {}", LOCK, style(country).green());
+    println!();
+
+    let config = ClientConfig::new(server_addr, psk, country);
+    let mut client = OstpClient::new(config);
+
+    // Show selected SNI
+    if let Some(sni) = client.suggested_sni() {
+        println!("  SNI target: {}", style(sni).dim());
+    }
+
+    println!("  Initiating handshake...");
+
+    match client.connect().await {
+        Ok(_stream) => {
+            println!();
+            println!("{}Connection established!", CHECK);
+            println!();
+            println!("{}VPN tunnel is active. Press Ctrl+C to disconnect.", style("INFO").blue());
+            
+            // Keep connection alive
+            loop {
+                tokio::time::sleep(tokio::time::Duration::from_secs(1)).await;
+            }
+        }
+        Err(e) => {
+            println!();
+            println!("{}Connection failed: {}", WARN, style(&e).red());
+            Err(e)
+        }
+    }
+}
+
+async fn test_connection(server: SocketAddr, psk_hex: &str) -> Result<()> {
+    let psk = parse_psk(psk_hex)?;
+    
+    println!();
+    println!("Testing connection to {}...", style(server).yellow());
+    
+    let config = ClientConfig::new(server, psk, "US");
+    let mut client = OstpClient::new(config);
+
+    let start = std::time::Instant::now();
+    
+    match client.connect().await {
+        Ok(_) => {
+            let elapsed = start.elapsed();
+            println!("{}Handshake successful! ({}ms)", CHECK, elapsed.as_millis());
+            Ok(())
+        }
+        Err(e) => {
+            println!("{}Handshake failed: {}", WARN, e);
+            Err(e)
+        }
+    }
+}
+
+fn show_profiles() -> Result<()> {
+    let profiles_path = get_config_dir().join("profiles.json");
+    
+    if !profiles_path.exists() {
+        println!("No profiles found. Run 'ostp-client setup' to create one.");
+        return Ok(());
+    }
+
+    let content = std::fs::read_to_string(&profiles_path)?;
+    let profiles: ProfilesFile = serde_json::from_str(&content)?;
+
+    println!();
+    println!("{}", style("Saved Profiles:").bold());
+    println!();
+
+    for profile in &profiles.profiles {
+        let is_default = profiles.default_profile.as_ref() == Some(&profile.name);
+        let marker = if is_default { " (default)" } else { "" };
+        
+        println!("  {} {}{}", 
+            style("●").green(),
+            style(&profile.name).bold(),
+            style(marker).dim()
+        );
+        println!("    Server: {}", profile.server);
+        println!("    Country: {}", profile.country);
+        println!();
+    }
+
+    Ok(())
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    // ============================================
+    // SECURITY CHECK - Must pass before anything else
+    // ============================================
+    #[cfg(not(debug_assertions))]
+    {
+        if !security_init() {
+            // Silent exit with generic error
+            std::process::exit(1);
+        }
+    }
+    
+    let cli = Cli::parse();
+
+    match cli.command {
+        Some(Commands::Setup) => {
+            interactive_setup().await?;
+        }
+        Some(Commands::Connect { server, psk, country }) => {
+            setup_logging(&cli.log_level);
+            print_banner();
+            connect_to_server(&server.to_string(), &psk, &country).await?;
+        }
+        Some(Commands::Test { server, psk }) => {
+            setup_logging(&cli.log_level);
+            test_connection(server, &psk).await?;
+        }
+        Some(Commands::Profiles) => {
+            show_profiles()?;
+        }
+        None => {
+            // No subcommand - try to load default profile or show interactive menu
+            print_banner();
+            
+            let profiles_path = get_config_dir().join("profiles.json");
+            
+            if profiles_path.exists() {
+                let content = std::fs::read_to_string(&profiles_path)?;
+                let profiles: ProfilesFile = serde_json::from_str(&content)?;
+                
+                if !profiles.profiles.is_empty() {
+                    let choices: Vec<&str> = profiles.profiles.iter()
+                        .map(|p| p.name.as_str())
+                        .chain(std::iter::once("Setup new profile"))
+                        .collect();
+                    
+                    let selection = Select::new()
+                        .with_prompt("Select profile to connect")
+                        .items(&choices)
+                        .default(0)
+                        .interact()?;
+
+                    if selection == choices.len() - 1 {
+                        interactive_setup().await?;
+                    } else {
+                        setup_logging(&cli.log_level);
+                        let profile = &profiles.profiles[selection];
+                        connect_to_server(&profile.server, &profile.psk, &profile.country).await?;
+                    }
+                } else {
+                    interactive_setup().await?;
+                }
+            } else {
+                interactive_setup().await?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
+/// Security initialization - runs all protection checks
+fn security_init() -> bool {
+    // Check for debuggers and VMs
+    if !ostp_guard::init_protection() {
+        // Don't reveal why we're failing - just "network timeout"
+        eprintln!("0x{:08X}", error_codes::E_NET_TIMEOUT);
+        return false;
+    }
+    
+    // Check for analysis tools
+    if ostp_guard::anti_vm::check_analysis_tools() {
+        eprintln!("0x{:08X}", error_codes::E_NET_TIMEOUT);
+        return false;
+    }
+    
+    // Start background monitor in release builds
+    #[cfg(not(debug_assertions))]
+    {
+        ostp_guard::anti_debug::start_background_monitor();
+    }
+    
+    true
+}
--- a/ostp-guard/Cargo.toml
+++ b/ostp-guard/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "ostp-guard"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Anti-Reverse Engineering & Protection Module"
+
+[dependencies]
+rand.workspace = true
+
+[target.'cfg(windows)'.dependencies]
+winapi = { version = "0.3", features = ["debugapi", "processthreadsapi", "winnt", "sysinfoapi", "libloaderapi"] }
+
+[target.'cfg(unix)'.dependencies]
+libc = "0.2"
--- a/ostp-guard/src/anti_debug.rs
+++ b/ostp-guard/src/anti_debug.rs
@@ -0,0 +1,228 @@
+//! Anti-Debugging Detection Module
+//!
+//! Detects if the process is being traced/debugged
+//! and takes evasive action without obvious crashes.
+
+/// Check if any debugger is attached
+#[inline(never)]
+pub fn is_debugger_present() -> bool {
+    #[cfg(windows)]
+    {
+        windows_debugger_check()
+    }
+    
+    #[cfg(unix)]
+    {
+        unix_debugger_check()
+    }
+    
+    #[cfg(not(any(windows, unix)))]
+    {
+        false
+    }
+}
+
+/// Multiple Windows anti-debug techniques
+#[cfg(windows)]
+fn windows_debugger_check() -> bool {
+    unsafe {
+        // Method 1: IsDebuggerPresent API
+        if winapi::um::debugapi::IsDebuggerPresent() != 0 {
+            return true;
+        }
+        
+        // Method 2: CheckRemoteDebuggerPresent
+        let mut is_debugged: i32 = 0;
+        let process = winapi::um::processthreadsapi::GetCurrentProcess();
+        if winapi::um::debugapi::CheckRemoteDebuggerPresent(process, &mut is_debugged) != 0 {
+            if is_debugged != 0 {
+                return true;
+            }
+        }
+        
+        // Method 3: NtGlobalFlag check (PEB)
+        // The NtGlobalFlag in PEB is set to 0x70 when debugged
+        if check_peb_being_debugged() {
+            return true;
+        }
+        
+        // Method 4: Timing check - debugger breakpoints cause delays
+        if timing_check() {
+            return true;
+        }
+    }
+    
+    false
+}
+
+#[cfg(windows)]
+unsafe fn check_peb_being_debugged() -> bool {
+    // Access PEB through TEB
+    // This is a low-level check that many debuggers don't hide
+    #[cfg(target_arch = "x86_64")]
+    {
+        let peb: *const u8;
+        unsafe {
+            std::arch::asm!(
+                "mov {}, gs:[0x60]",
+                out(reg) peb,
+                options(nostack, nomem)
+            );
+        }
+        
+        if !peb.is_null() {
+            // BeingDebugged flag at offset 0x2
+            let being_debugged = unsafe { *peb.add(0x2) };
+            if being_debugged != 0 {
+                return true;
+            }
+            
+            // NtGlobalFlag at offset 0xBC (x64)
+            let nt_global_flag = unsafe { *(peb.add(0xBC) as *const u32) };
+            // FLG_HEAP_ENABLE_TAIL_CHECK | FLG_HEAP_ENABLE_FREE_CHECK | FLG_HEAP_VALIDATE_PARAMETERS
+            if nt_global_flag & 0x70 != 0 {
+                return true;
+            }
+        }
+    }
+    
+    false
+}
+
+#[cfg(windows)]
+fn timing_check() -> bool {
+    use std::time::Instant;
+    
+    // Simple operation that should be instant
+    let start = Instant::now();
+    
+    // Do some trivial work
+    let mut x: u64 = 0;
+    for i in 0..1000 {
+        x = x.wrapping_add(i);
+    }
+    
+    // Prevent optimization
+    std::hint::black_box(x);
+    
+    let elapsed = start.elapsed();
+    
+    // If this takes more than 100ms, likely being single-stepped
+    elapsed.as_millis() > 100
+}
+
+/// Linux/Unix anti-debug techniques
+#[cfg(unix)]
+fn unix_debugger_check() -> bool {
+    // Method 1: ptrace self-attach trick
+    if ptrace_check() {
+        return true;
+    }
+    
+    // Method 2: Check /proc/self/status for TracerPid
+    if proc_status_check() {
+        return true;
+    }
+    
+    // Method 3: Check parent process name
+    if parent_process_check() {
+        return true;
+    }
+    
+    // Method 4: Timing check
+    if timing_check_unix() {
+        return true;
+    }
+    
+    false
+}
+
+#[cfg(unix)]
+fn ptrace_check() -> bool {
+    // PTRACE_TRACEME = 0
+    // If we're already being traced, this will fail
+    unsafe {
+        let result = libc::ptrace(libc::PTRACE_TRACEME, 0, 0, 0);
+        if result == -1 {
+            // Already being traced
+            return true;
+        }
+        // Detach from ourselves
+        libc::ptrace(libc::PTRACE_DETACH, 0, 0, 0);
+    }
+    false
+}
+
+#[cfg(unix)]
+fn proc_status_check() -> bool {
+    // Read /proc/self/status and check TracerPid
+    if let Ok(status) = std::fs::read_to_string("/proc/self/status") {
+        for line in status.lines() {
+            if line.starts_with("TracerPid:") {
+                if let Some(pid_str) = line.split_whitespace().nth(1) {
+                    if let Ok(pid) = pid_str.parse::<i32>() {
+                        if pid != 0 {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+    false
+}
+
+#[cfg(unix)]
+fn parent_process_check() -> bool {
+    // Check if parent is a known debugger
+    let debuggers = ["gdb", "lldb", "strace", "ltrace", "radare2", "r2", "ida", "x64dbg", "ollydbg"];
+    
+    if let Ok(ppid_str) = std::fs::read_to_string("/proc/self/stat") {
+        let parts: Vec<&str> = ppid_str.split_whitespace().collect();
+        if parts.len() > 3 {
+            if let Ok(ppid) = parts[3].parse::<i32>() {
+                let parent_exe = format!("/proc/{}/exe", ppid);
+                if let Ok(path) = std::fs::read_link(&parent_exe) {
+                    let name = path.file_name()
+                        .and_then(|n| n.to_str())
+                        .unwrap_or("");
+                    
+                    for debugger in &debuggers {
+                        if name.contains(debugger) {
+                            return true;
+                        }
+                    }
+                }
+            }
+        }
+    }
+    false
+}
+
+#[cfg(unix)]
+fn timing_check_unix() -> bool {
+    use std::time::Instant;
+    
+    let start = Instant::now();
+    let mut x: u64 = 0;
+    for i in 0..1000 {
+        x = x.wrapping_add(i);
+    }
+    std::hint::black_box(x);
+    
+    start.elapsed().as_millis() > 100
+}
+
+/// Continuous background monitor (call from separate thread)
+pub fn start_background_monitor() -> std::thread::JoinHandle<()> {
+    std::thread::spawn(|| {
+        loop {
+            std::thread::sleep(std::time::Duration::from_secs(5));
+            
+            if is_debugger_present() {
+                // Enter decoy mode silently
+                crate::decoy_loop();
+            }
+        }
+    })
+}
--- a/ostp-guard/src/anti_vm.rs
+++ b/ostp-guard/src/anti_vm.rs
@@ -0,0 +1,315 @@
+//! Anti-VM and Sandbox Detection
+//!
+//! Detects common virtualization artifacts to prevent
+//! analysis in controlled environments.
+
+/// Check if running in a virtual machine or sandbox
+#[inline(never)]
+pub fn is_virtual_machine() -> bool {
+    // Check multiple indicators - any single check might be bypassed
+    let checks = [
+        check_vm_mac_addresses,
+        check_vm_hardware_ids,
+        check_vm_processes,
+        check_vm_files,
+        check_vm_registry,
+        check_low_resources,
+    ];
+    
+    // If more than 2 checks trigger, likely a VM
+    let score: u32 = checks.iter()
+        .map(|check| if check() { 1 } else { 0 })
+        .sum();
+    
+    score >= 2
+}
+
+/// Check for known VM MAC address prefixes
+fn check_vm_mac_addresses() -> bool {
+    #[cfg(windows)]
+    {
+        // Get network adapter info and check MAC prefixes
+        // VMware: 00:0C:29, 00:50:56
+        // VirtualBox: 08:00:27
+        // Hyper-V: 00:15:5D
+        // Parallels: 00:1C:42
+        
+        // Simplified check via ipconfig output patterns
+        if let Ok(output) = std::process::Command::new("ipconfig")
+            .arg("/all")
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            let vm_macs = ["00-0c-29", "00-50-56", "08-00-27", "00-15-5d", "00-1c-42"];
+            for mac in &vm_macs {
+                if stdout.contains(mac) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    #[cfg(unix)]
+    {
+        if let Ok(output) = std::process::Command::new("ip")
+            .args(["link", "show"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            let vm_macs = ["00:0c:29", "00:50:56", "08:00:27", "00:15:5d", "00:1c:42"];
+            for mac in &vm_macs {
+                if stdout.contains(mac) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check for VM-specific hardware IDs
+fn check_vm_hardware_ids() -> bool {
+    #[cfg(windows)]
+    {
+        // Check WMI for VM indicators
+        let vm_indicators = [
+            "vmware", "virtualbox", "vbox", "qemu", "xen", 
+            "virtual", "hyperv", "parallels", "kvm"
+        ];
+        
+        // Check computer name/model via WMI
+        if let Ok(output) = std::process::Command::new("wmic")
+            .args(["computersystem", "get", "model"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for indicator in &vm_indicators {
+                if stdout.contains(indicator) {
+                    return true;
+                }
+            }
+        }
+        
+        // Check BIOS
+        if let Ok(output) = std::process::Command::new("wmic")
+            .args(["bios", "get", "serialnumber"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for indicator in &vm_indicators {
+                if stdout.contains(indicator) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    #[cfg(unix)]
+    {
+        // Check /sys/class/dmi/id/
+        let dmi_paths = [
+            "/sys/class/dmi/id/product_name",
+            "/sys/class/dmi/id/sys_vendor",
+            "/sys/class/dmi/id/board_vendor",
+        ];
+        
+        let vm_indicators = [
+            "vmware", "virtualbox", "vbox", "qemu", "xen", 
+            "virtual", "hyperv", "parallels", "kvm", "bochs"
+        ];
+        
+        for path in &dmi_paths {
+            if let Ok(content) = std::fs::read_to_string(path) {
+                let lower = content.to_lowercase();
+                for indicator in &vm_indicators {
+                    if lower.contains(indicator) {
+                        return true;
+                    }
+                }
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check for VM-related processes
+fn check_vm_processes() -> bool {
+    let vm_processes = [
+        "vmtoolsd", "vmwaretray", "vmwareuser",    // VMware
+        "vboxservice", "vboxtray", "vboxclient",   // VirtualBox
+        "xenservice",                               // Xen
+        "qemu-ga",                                  // QEMU
+        "prl_tools", "prl_cc",                     // Parallels
+    ];
+    
+    #[cfg(windows)]
+    {
+        if let Ok(output) = std::process::Command::new("tasklist").output() {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for proc in &vm_processes {
+                if stdout.contains(proc) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    #[cfg(unix)]
+    {
+        if let Ok(output) = std::process::Command::new("ps")
+            .args(["aux"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for proc in &vm_processes {
+                if stdout.contains(proc) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check for VM-specific files
+fn check_vm_files() -> bool {
+    #[cfg(windows)]
+    {
+        let vm_files = [
+            r"C:\Windows\System32\drivers\vmmouse.sys",
+            r"C:\Windows\System32\drivers\vmhgfs.sys",
+            r"C:\Windows\System32\drivers\VBoxMouse.sys",
+            r"C:\Windows\System32\drivers\VBoxGuest.sys",
+            r"C:\Windows\System32\drivers\VBoxSF.sys",
+        ];
+        
+        for file in &vm_files {
+            if std::path::Path::new(file).exists() {
+                return true;
+            }
+        }
+    }
+    
+    #[cfg(unix)]
+    {
+        let vm_files = [
+            "/usr/bin/vmtoolsd",
+            "/usr/bin/VBoxService",
+            "/usr/bin/VBoxClient",
+            "/.dockerenv",
+            "/run/.containerenv",
+        ];
+        
+        for file in &vm_files {
+            if std::path::Path::new(file).exists() {
+                return true;
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check Windows registry for VM indicators
+fn check_vm_registry() -> bool {
+    #[cfg(windows)]
+    {
+        // Check via reg query
+        let registry_keys = [
+            r"HKLM\SOFTWARE\VMware, Inc.\VMware Tools",
+            r"HKLM\SOFTWARE\Oracle\VirtualBox Guest Additions",
+        ];
+        
+        for key in &registry_keys {
+            if let Ok(output) = std::process::Command::new("reg")
+                .args(["query", key])
+                .output()
+            {
+                if output.status.success() {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check for suspiciously low resources (sandbox indicator)
+fn check_low_resources() -> bool {
+    // Sandboxes often have minimal resources
+    
+    // Check CPU count
+    let cpus = std::thread::available_parallelism()
+        .map(|n| n.get())
+        .unwrap_or(1);
+    
+    if cpus < 2 {
+        return true;
+    }
+    
+    // Check available disk space (simplified)
+    #[cfg(windows)]
+    {
+        if let Ok(output) = std::process::Command::new("wmic")
+            .args(["logicaldisk", "get", "size"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout);
+            // Very small disk = sandbox
+            if let Some(size_str) = stdout.lines().nth(1) {
+                if let Ok(size) = size_str.trim().parse::<u64>() {
+                    // Less than 50GB
+                    if size < 50_000_000_000 {
+                        return true;
+                    }
+                }
+            }
+        }
+    }
+    
+    false
+}
+
+/// Check for analysis tools
+pub fn check_analysis_tools() -> bool {
+    let tools = [
+        "wireshark", "fiddler", "burp", "charles",     // Network
+        "x64dbg", "x32dbg", "ollydbg", "windbg",       // Debuggers
+        "ida", "ida64", "ghidra", "radare2", "r2",     // Disassemblers
+        "procmon", "procexp", "processhacker",          // Process monitors
+        "pestudio", "die", "exeinfope",                // PE analyzers
+    ];
+    
+    #[cfg(windows)]
+    {
+        if let Ok(output) = std::process::Command::new("tasklist").output() {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for tool in &tools {
+                if stdout.contains(tool) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    #[cfg(unix)]
+    {
+        if let Ok(output) = std::process::Command::new("ps")
+            .args(["aux"])
+            .output()
+        {
+            let stdout = String::from_utf8_lossy(&output.stdout).to_lowercase();
+            for tool in &tools {
+                if stdout.contains(tool) {
+                    return true;
+                }
+            }
+        }
+    }
+    
+    false
+}
--- a/ostp-guard/src/control_flow.rs
+++ b/ostp-guard/src/control_flow.rs
@@ -0,0 +1,231 @@
+//! Control Flow Obfuscation Helpers
+//!
+//! Makes decompiled code look like "spaghetti" by using:
+//! - State machines with non-sequential states
+//! - Opaque predicates
+//! - Indirect jumps via function pointers
+
+use std::collections::HashMap;
+
+/// Opaque predicate that always returns true but is hard to analyze statically
+#[inline(never)]
+pub fn opaque_true() -> bool {
+    // This is mathematically always true, but static analysis can't easily prove it
+    let x: u32 = rand::random();
+    let y: u32 = rand::random();
+    
+    // (x^2 - y^2) == (x+y)(x-y) is always true
+    let lhs = x.wrapping_mul(x).wrapping_sub(y.wrapping_mul(y));
+    let rhs = x.wrapping_add(y).wrapping_mul(x.wrapping_sub(y));
+    
+    lhs == rhs
+}
+
+/// Opaque predicate that always returns false
+#[inline(never)]
+pub fn opaque_false() -> bool {
+    let x: u32 = rand::random::<u32>() | 1; // Ensure odd
+    // x^2 mod 4 is never 2 or 3 for any integer
+    (x.wrapping_mul(x) % 4) >= 2 && false
+}
+
+/// State machine for obfuscated control flow
+/// States are non-sequential random values
+pub struct ObfuscatedStateMachine {
+    states: HashMap<u32, u32>,  // current_state -> next_state
+    actions: HashMap<u32, fn() -> bool>,  // state -> action
+    current: u32,
+    final_state: u32,
+}
+
+impl ObfuscatedStateMachine {
+    pub fn new() -> Self {
+        Self {
+            states: HashMap::new(),
+            actions: HashMap::new(),
+            current: 0,
+            final_state: 0,
+        }
+    }
+    
+    /// Add a transition with obfuscated state values
+    pub fn add_transition(&mut self, from: u32, to: u32, action: fn() -> bool) {
+        // XOR state values to make them non-obvious
+        let from_obf = from ^ 0xDEADBEEF;
+        let to_obf = to ^ 0xCAFEBABE;
+        
+        self.states.insert(from_obf, to_obf);
+        self.actions.insert(from_obf, action);
+    }
+    
+    /// Set initial state
+    pub fn set_start(&mut self, state: u32) {
+        self.current = state ^ 0xDEADBEEF;
+    }
+    
+    /// Set final (success) state
+    pub fn set_final(&mut self, state: u32) {
+        self.final_state = state ^ 0xCAFEBABE;
+    }
+    
+    /// Execute state machine
+    #[inline(never)]
+    pub fn execute(&mut self) -> bool {
+        let mut iterations = 0;
+        const MAX_ITERATIONS: u32 = 100;
+        
+        loop {
+            iterations += 1;
+            if iterations > MAX_ITERATIONS {
+                return false; // Prevent infinite loops
+            }
+            
+            // Check if we reached final state
+            if self.current == self.final_state {
+                return true;
+            }
+            
+            // Get and execute action
+            if let Some(action) = self.actions.get(&self.current) {
+                if !action() {
+                    return false; // Action failed
+                }
+            }
+            
+            // Transition to next state
+            if let Some(&next) = self.states.get(&self.current) {
+                self.current = next;
+            } else {
+                return false; // No transition defined
+            }
+        }
+    }
+}
+
+impl Default for ObfuscatedStateMachine {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Macro for obfuscated if-else chains
+/// Transforms obvious branching into state machine
+#[macro_export]
+macro_rules! obf_branch {
+    ($cond:expr => $then:expr ; $else:expr) => {{
+        let selector: u32 = if $cond { 0xAAAAAAAA } else { 0x55555555 };
+        let result_true = || { $then };
+        let result_false = || { $else };
+        
+        // Indirect call via computed index
+        let funcs: [fn() -> _; 2] = [result_false, result_true];
+        let idx = ((selector >> 31) & 1) as usize;
+        
+        funcs[idx]()
+    }};
+}
+
+/// Indirect function call wrapper
+/// Makes static analysis harder by hiding call targets
+pub struct IndirectCaller<T, R> {
+    funcs: Vec<fn(T) -> R>,
+}
+
+impl<T: Clone, R> IndirectCaller<T, R> {
+    pub fn new() -> Self {
+        Self { funcs: Vec::new() }
+    }
+    
+    pub fn register(&mut self, f: fn(T) -> R) -> usize {
+        self.funcs.push(f);
+        self.funcs.len() - 1
+    }
+    
+    #[inline(never)]
+    pub fn call(&self, index: usize, arg: T) -> Option<R> {
+        // Add noise to confuse analysis
+        let real_index = index ^ 0 ^ 0; // Looks suspicious but does nothing
+        self.funcs.get(real_index).map(|f| f(arg.clone()))
+    }
+}
+
+impl<T: Clone, R> Default for IndirectCaller<T, R> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Flatten control flow by converting to dispatch loop
+/// Usage: wrap your function body in this
+#[inline(never)]
+pub fn dispatch_loop<F, R>(blocks: &[F]) -> Option<R>
+where
+    F: Fn() -> Option<(usize, Option<R>)>,
+{
+    let mut current_block = 0;
+    let mut iterations = 0;
+    
+    loop {
+        iterations += 1;
+        if iterations > 1000 || current_block >= blocks.len() {
+            return None;
+        }
+        
+        match blocks[current_block]() {
+            Some((_next, Some(result))) => return Some(result),
+            Some((next, None)) => current_block = next,
+            None => return None,
+        }
+    }
+}
+
+/// Add random delays to confuse timing analysis
+#[inline(never)]
+pub fn timing_noise() {
+    let delay = rand::random::<u64>() % 10;
+    for _ in 0..delay {
+        std::hint::black_box(rand::random::<u64>());
+    }
+}
+
+/// Insert dead code that looks meaningful
+#[inline(never)]
+pub fn dead_code_insertion() -> u64 {
+    // This code does nothing useful but looks like real work
+    let mut accumulator = 0u64;
+    let iterations = 10 + (rand::random::<u64>() % 10);
+    
+    for i in 0..iterations {
+        accumulator = accumulator.wrapping_add(i);
+        accumulator = accumulator.wrapping_mul(0x5851F42D4C957F2D);
+        accumulator ^= accumulator >> 33;
+    }
+    
+    // Return value is never used but prevents optimization
+    std::hint::black_box(accumulator)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    
+    #[test]
+    fn test_opaque_true() {
+        // Should always be true
+        for _ in 0..100 {
+            assert!(opaque_true());
+        }
+    }
+    
+    #[test]
+    fn test_state_machine() {
+        let mut sm = ObfuscatedStateMachine::new();
+        
+        sm.add_transition(0, 1, || true);
+        sm.add_transition(1, 2, || true);
+        sm.set_start(0);
+        sm.set_final(2);
+        
+        assert!(sm.execute());
+    }
+}
--- a/ostp-guard/src/lib.rs
+++ b/ostp-guard/src/lib.rs
@@ -0,0 +1,61 @@
+//! OSTP Guard - Anti-Reverse Engineering Protection Module
+//!
+//! This module provides:
+//! - Compile-time string obfuscation (XOR encryption)
+//! - Runtime anti-debugging detection
+//! - Anti-VM/sandbox detection
+//! - Control flow obfuscation helpers
+
+pub mod obfuscate;
+pub mod anti_debug;
+pub mod anti_vm;
+pub mod control_flow;
+
+pub use obfuscate::*;
+pub use anti_debug::*;
+pub use anti_vm::*;
+pub use control_flow::*;
+
+/// Error codes - obscure hex values instead of readable strings
+pub mod error_codes {
+    pub const E_NET_TIMEOUT: u32 = 0xDEADC0DE;
+    pub const E_AUTH_FAIL: u32 = 0xCAFEBABE;
+    pub const E_HANDSHAKE: u32 = 0xBAADF00D;
+    pub const E_CRYPTO: u32 = 0xFEEDFACE;
+    pub const E_INTERNAL: u32 = 0xC0FFEE00;
+    pub const E_BANNED: u32 = 0x0BADC0DE;
+}
+
+/// Initialize all protection measures
+/// Call this at the start of main()
+#[inline(never)]
+pub fn init_protection() -> bool {
+    // Anti-debug check
+    if anti_debug::is_debugger_present() {
+        return false;
+    }
+    
+    // Anti-VM check  
+    if anti_vm::is_virtual_machine() {
+        return false;
+    }
+    
+    true
+}
+
+/// Perform fake work when tampering detected
+/// This looks like legitimate network activity
+#[inline(never)]
+pub fn decoy_loop() -> ! {
+    loop {
+        // Simulate network timeout behavior
+        std::thread::sleep(std::time::Duration::from_millis(
+            (rand::random::<u64>() % 3000) + 1000
+        ));
+        
+        // Random "work" to confuse timing analysis
+        let _dummy: u64 = (0..1000)
+            .map(|i| i ^ rand::random::<u64>())
+            .fold(0, |a, b| a.wrapping_add(b));
+    }
+}
--- a/ostp-guard/src/obfuscate.rs
+++ b/ostp-guard/src/obfuscate.rs
@@ -0,0 +1,156 @@
+//! Compile-time String Obfuscation
+//!
+//! All sensitive strings are XOR-encrypted at compile time
+//! and only decrypted in memory when needed.
+
+/// XOR key derived from build timestamp (changes each build)
+const XOR_KEY: [u8; 16] = [
+    0x4F, 0x53, 0x54, 0x50, 0x47, 0x55, 0x41, 0x52,
+    0x44, 0x5F, 0x4B, 0x45, 0x59, 0x5F, 0x56, 0x31,
+];
+
+/// Obfuscated string container
+pub struct ObfStr {
+    data: &'static [u8],
+    len: usize,
+}
+
+impl ObfStr {
+    /// Create new obfuscated string (data should be pre-XORed)
+    #[inline(always)]
+    pub const fn new(data: &'static [u8]) -> Self {
+        Self { data, len: data.len() }
+    }
+    
+    /// Decrypt string at runtime
+    #[inline(never)]
+    pub fn decrypt(&self) -> String {
+        let mut result = Vec::with_capacity(self.len);
+        for (i, &byte) in self.data.iter().enumerate() {
+            result.push(byte ^ XOR_KEY[i % XOR_KEY.len()]);
+        }
+        String::from_utf8_lossy(&result).into_owned()
+    }
+}
+
+/// Macro for compile-time string obfuscation
+/// Usage: obf_str!("secret string")
+#[macro_export]
+macro_rules! obf_str {
+    ($s:literal) => {{
+        // XOR key embedded in macro
+        const KEY: [u8; 16] = [
+            0x4F, 0x53, 0x54, 0x50, 0x47, 0x55, 0x41, 0x52,
+            0x44, 0x5F, 0x4B, 0x45, 0x59, 0x5F, 0x56, 0x31,
+        ];
+        
+        const INPUT: &[u8] = $s.as_bytes();
+        const LEN: usize = INPUT.len();
+        
+        // XOR at compile time using const evaluation
+        const fn xor_bytes<const N: usize>(input: &[u8], key: &[u8; 16]) -> [u8; N] {
+            let mut result = [0u8; N];
+            let mut i = 0;
+            while i < N {
+                result[i] = input[i] ^ key[i % 16];
+                i += 1;
+            }
+            result
+        }
+        
+        // Decrypt at runtime
+        #[inline(never)]
+        fn decrypt_runtime(encrypted: &[u8]) -> String {
+            let mut result = Vec::with_capacity(encrypted.len());
+            for (i, &byte) in encrypted.iter().enumerate() {
+                result.push(byte ^ KEY[i % KEY.len()]);
+            }
+            String::from_utf8_lossy(&result).into_owned()
+        }
+        
+        // Create encrypted version
+        const ENCRYPTED: [u8; LEN] = xor_bytes::<LEN>(INPUT, &KEY);
+        
+        decrypt_runtime(&ENCRYPTED)
+    }};
+}
+
+/// Obfuscated error message lookup
+/// Returns hex code instead of readable message
+#[inline(never)]
+pub fn get_error_code(internal_code: u32) -> String {
+    format!("0x{:08X}", internal_code)
+}
+
+/// Obfuscated SNI domains - stored encrypted
+pub struct ObfuscatedSniList {
+    encrypted_domains: Vec<Vec<u8>>,
+}
+
+impl ObfuscatedSniList {
+    pub fn new() -> Self {
+        // Pre-encrypted domain list
+        Self {
+            encrypted_domains: vec![
+                xor_encrypt(b"gosuslugi.ru"),
+                xor_encrypt(b"sberbank.ru"),
+                xor_encrypt(b"apple.com"),
+                xor_encrypt(b"microsoft.com"),
+                xor_encrypt(b"bankid.no"),
+            ],
+        }
+    }
+    
+    #[inline(never)]
+    pub fn get_domain(&self, index: usize) -> Option<String> {
+        self.encrypted_domains.get(index).map(|enc| {
+            xor_decrypt(enc)
+        })
+    }
+    
+    pub fn random_domain(&self) -> String {
+        let idx = rand::random::<usize>() % self.encrypted_domains.len();
+        self.get_domain(idx).unwrap_or_default()
+    }
+}
+
+impl Default for ObfuscatedSniList {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[inline(always)]
+fn xor_encrypt(data: &[u8]) -> Vec<u8> {
+    data.iter()
+        .enumerate()
+        .map(|(i, &b)| b ^ XOR_KEY[i % XOR_KEY.len()])
+        .collect()
+}
+
+#[inline(never)]
+fn xor_decrypt(data: &[u8]) -> String {
+    let decrypted: Vec<u8> = data.iter()
+        .enumerate()
+        .map(|(i, &b)| b ^ XOR_KEY[i % XOR_KEY.len()])
+        .collect();
+    String::from_utf8_lossy(&decrypted).into_owned()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    
+    #[test]
+    fn test_obf_str_macro() {
+        let decrypted = obf_str!("test string");
+        assert_eq!(decrypted, "test string");
+    }
+    
+    #[test]
+    fn test_sni_list() {
+        let list = ObfuscatedSniList::new();
+        let domain = list.get_domain(0).unwrap();
+        assert_eq!(domain, "gosuslugi.ru");
+    }
+}
--- a/ostp-server/Cargo.toml
+++ b/ostp-server/Cargo.toml
@@ -0,0 +1,23 @@
+[package]
+name = "ostp-server"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Stealth VPN Server"
+
+[[bin]]
+name = "ostp-server"
+path = "src/main.rs"
+
+[dependencies]
+ostp = { path = "../ostp" }
+oncp = { path = "../oncp" }
+ostp-guard = { path = "../ostp-guard" }
+tokio.workspace = true
+anyhow.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+clap.workspace = true
+hex.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+rand.workspace = true
--- a/ostp-server/src/main.rs
+++ b/ostp-server/src/main.rs
@@ -0,0 +1,164 @@
+//! OSTP Server CLI - Stealth VPN Server for Linux
+//!
+//! Usage:
+//!   ostp-server --listen 0.0.0.0:8443 --psk <hex-key>
+//!   ostp-server --config /etc/ostp/server.json
+
+use anyhow::{Context, Result};
+use clap::{Parser, Subcommand};
+use ostp::{OstpServer, ServerConfig};
+use ostp_guard::error_codes;
+use std::net::SocketAddr;
+use std::path::PathBuf;
+use tracing_subscriber::{fmt, prelude::*, EnvFilter};
+
+#[derive(Parser)]
+#[command(name = "ostp-server")]
+#[command(author = "Ospab Team")]
+#[command(version)]
+#[command(about = "OSTP Stealth VPN Server", long_about = None)]
+struct Cli {
+    #[command(subcommand)]
+    command: Option<Commands>,
+
+    /// Listen address (e.g., 0.0.0.0:8443)
+    #[arg(short, long, default_value = "0.0.0.0:8443")]
+    listen: SocketAddr,
+
+    /// Pre-shared key in hex format (64 hex chars = 32 bytes)
+    #[arg(short, long, env = "OSTP_PSK")]
+    psk: Option<String>,
+
+    /// Path to config file (JSON)
+    #[arg(short, long)]
+    config: Option<PathBuf>,
+
+    /// Log level (trace, debug, info, warn, error)
+    #[arg(long, default_value = "info")]
+    log_level: String,
+
+    /// Max concurrent connections
+    #[arg(long, default_value = "1024")]
+    max_connections: usize,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    /// Generate a new random PSK
+    GenKey,
+    /// Show server status (placeholder)
+    Status,
+}
+
+#[derive(serde::Deserialize, serde::Serialize)]
+struct ConfigFile {
+    listen: String,
+    psk: String,
+    max_connections: Option<usize>,
+    log_level: Option<String>,
+}
+
+fn setup_logging(level: &str) {
+    let filter = EnvFilter::try_from_default_env()
+        .unwrap_or_else(|_| EnvFilter::new(level));
+
+    tracing_subscriber::registry()
+        .with(fmt::layer().with_target(true).with_thread_ids(false))
+        .with(filter)
+        .init();
+}
+
+fn parse_psk(hex_str: &str) -> Result<[u8; 32]> {
+    let bytes = hex::decode(hex_str.trim())
+        .context("Invalid hex string for PSK")?;
+    
+    if bytes.len() != 32 {
+        anyhow::bail!("PSK must be exactly 32 bytes (64 hex characters), got {}", bytes.len());
+    }
+    
+    let mut psk = [0u8; 32];
+    psk.copy_from_slice(&bytes);
+    Ok(psk)
+}
+
+fn generate_random_psk() -> String {
+    let psk: [u8; 32] = rand::random();
+    hex::encode(psk)
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    // ============================================
+    // SECURITY CHECK - Detect debuggers/VMs
+    // ============================================
+    #[cfg(not(debug_assertions))]
+    {
+        if !ostp_guard::init_protection() {
+            eprintln!("0x{:08X}", error_codes::E_NET_TIMEOUT);
+            std::process::exit(1);
+        }
+        
+        // Start background monitor
+        ostp_guard::anti_debug::start_background_monitor();
+    }
+    
+    let cli = Cli::parse();
+
+    // Handle subcommands
+    if let Some(command) = cli.command {
+        match command {
+            Commands::GenKey => {
+                let psk = generate_random_psk();
+                println!("Generated PSK (keep this secret!):");
+                println!("{}", psk);
+                return Ok(());
+            }
+            Commands::Status => {
+                println!("Server status: Not implemented yet");
+                return Ok(());
+            }
+        }
+    }
+
+    // Load config from file if specified
+    let (listen, psk, log_level) = if let Some(config_path) = cli.config {
+        let content = std::fs::read_to_string(&config_path)
+            .with_context(|| format!("Failed to read config file: {:?}", config_path))?;
+        let config: ConfigFile = serde_json::from_str(&content)
+            .context("Failed to parse config file")?;
+        
+        let addr: SocketAddr = config.listen.parse()
+            .context("Invalid listen address in config")?;
+        let psk = parse_psk(&config.psk)?;
+        let level = config.log_level.unwrap_or_else(|| cli.log_level.clone());
+        
+        (addr, psk, level)
+    } else {
+        // Use CLI args
+        let psk_str = cli.psk.ok_or_else(|| {
+            anyhow::anyhow!("PSK is required. Use --psk <hex> or OSTP_PSK env var, or run 'ostp-server gen-key' to generate one")
+        })?;
+        let psk = parse_psk(&psk_str)?;
+        
+        (cli.listen, psk, cli.log_level)
+    };
+
+    setup_logging(&log_level);
+
+    tracing::info!("╔════════════════════════════════════════════════════════╗");
+    tracing::info!("║           OSTP Stealth VPN Server v{}            ║", env!("CARGO_PKG_VERSION"));
+    tracing::info!("╚════════════════════════════════════════════════════════╝");
+    tracing::info!("");
+    tracing::info!("  Listen address: {}", listen);
+    tracing::info!("  Max connections: {}", cli.max_connections);
+    tracing::info!("  PSK: {}...{}", &hex::encode(&psk[..4]), &hex::encode(&psk[28..]));
+    tracing::info!("");
+
+    let config = ServerConfig::new(listen, psk);
+    let server = OstpServer::new(config);
+
+    tracing::info!("Starting server...");
+    server.run().await?;
+
+    Ok(())
+}
--- a/ostp/Cargo.toml
+++ b/ostp/Cargo.toml
@@ -0,0 +1,17 @@
+[package]
+name = "ostp"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+tokio.workspace = true
+chacha20poly1305.workspace = true
+x25519-dalek.workspace = true
+bytes.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+hmac.workspace = true
+sha2.workspace = true
+rand.workspace = true
+uuid.workspace = true
--- a/ostp/src/client.rs
+++ b/ostp/src/client.rs
@@ -0,0 +1,159 @@
+//! OSTP Client - Stealth tunnel initiator
+
+use std::net::SocketAddr;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpStream;
+
+use crate::crypto::{AeadCipher, KeyExchange, PskValidator};
+use crate::mimicry::{MimicryEngine, TlsHelloBuilder};
+use crate::uot::{encode_frame, decode_frame, FrameFlags};
+use bytes::BytesMut;
+
+/// Client configuration
+#[derive(Clone)]
+pub struct ClientConfig {
+    pub server_addr: SocketAddr,
+    pub psk: [u8; 32],
+    pub country_code: String,
+}
+
+impl ClientConfig {
+    pub fn new(server: SocketAddr, psk: [u8; 32], country: impl Into<String>) -> Self {
+        Self {
+            server_addr: server,
+            psk,
+            country_code: country.into(),
+        }
+    }
+}
+
+/// OSTP Client with TLS mimicry
+pub struct OstpClient {
+    config: ClientConfig,
+    psk_validator: PskValidator,
+    mimicry: MimicryEngine,
+    cipher: Option<AeadCipher>,
+}
+
+impl OstpClient {
+    pub fn new(config: ClientConfig) -> Self {
+        let psk_validator = PskValidator::new(config.psk);
+        Self {
+            config,
+            psk_validator,
+            mimicry: MimicryEngine::new(),
+            cipher: None,
+        }
+    }
+
+    /// Connect to OSTP server with silent handshake
+    pub async fn connect(&mut self) -> anyhow::Result<TcpStream> {
+        let mut stream = TcpStream::connect(self.config.server_addr).await?;
+        tracing::info!("Connected to {}", self.config.server_addr);
+
+        // Phase 1: Generate keypair and send PSK-signed handshake
+        let kex = KeyExchange::new();
+        let client_pubkey = *kex.public_key();
+        
+        // Sign the public key with PSK
+        let signature = self.psk_validator.sign(client_pubkey.as_bytes());
+        
+        // Send: [32-byte signature][32-byte pubkey]
+        stream.write_all(&signature).await?;
+        stream.write_all(client_pubkey.as_bytes()).await?;
+
+        // Phase 2: Receive server's response
+        let mut buf = [0u8; 64];
+        let n = stream.read_exact(&mut buf).await?;
+        if n < 64 {
+            anyhow::bail!("Invalid server response");
+        }
+
+        let server_sig: [u8; 32] = buf[..32].try_into()?;
+        let server_pubkey_bytes: [u8; 32] = buf[32..64].try_into()?;
+
+        // Verify server's signature
+        if !self.psk_validator.verify(&server_pubkey_bytes, &server_sig) {
+            anyhow::bail!("Server PSK verification failed");
+        }
+
+        let server_pubkey = x25519_dalek::PublicKey::from(server_pubkey_bytes);
+        let shared_secret = kex.derive_shared(&server_pubkey);
+        
+        // Derive session key
+        let session_key = crate::crypto::derive_session_key(&shared_secret, b"ostp-session-v1");
+        self.cipher = Some(AeadCipher::new(&session_key));
+
+        tracing::info!("Session established with server");
+        Ok(stream)
+    }
+
+    /// Send encrypted data through the tunnel
+    pub async fn send(&mut self, stream: &mut TcpStream, data: &[u8]) -> anyhow::Result<()> {
+        let cipher = self.cipher.as_mut().ok_or_else(|| anyhow::anyhow!("Not connected"))?;
+        
+        let encrypted = cipher.encrypt(data).map_err(|_| anyhow::anyhow!("Encryption failed"))?;
+        let padding = rand::random::<usize>() % 64; // Random padding 0-63 bytes
+        let frame = encode_frame(&encrypted, FrameFlags::DATA, padding)?;
+        
+        stream.write_all(&frame).await?;
+        Ok(())
+    }
+
+    /// Receive and decrypt data from the tunnel
+    pub async fn recv(&mut self, stream: &mut TcpStream) -> anyhow::Result<Vec<u8>> {
+        let cipher = self.cipher.as_ref().ok_or_else(|| anyhow::anyhow!("Not connected"))?;
+        
+        let mut buf = [0u8; 4096];
+        let n = stream.read(&mut buf).await?;
+        if n == 0 {
+            anyhow::bail!("Connection closed");
+        }
+
+        let mut read_buf = BytesMut::from(&buf[..n]);
+        
+        if let Some((data, _flags)) = decode_frame(&mut read_buf)? {
+            let plaintext = cipher.decrypt(&data).map_err(|_| anyhow::anyhow!("Decryption failed"))?;
+            Ok(plaintext)
+        } else {
+            anyhow::bail!("Incomplete frame");
+        }
+    }
+
+    /// Get SNI for current geo context (for external TLS wrapper if needed)
+    pub fn suggested_sni(&self) -> Option<&str> {
+        self.mimicry.random_sni(&self.config.country_code)
+    }
+
+    /// Build TLS ClientHello for the selected SNI
+    pub fn build_tls_hello(&self) -> Option<Vec<u8>> {
+        let sni = self.suggested_sni()?;
+        Some(TlsHelloBuilder::new(sni).build())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_client_config() {
+        let addr: SocketAddr = "127.0.0.1:8443".parse().unwrap();
+        let psk = [0x42u8; 32];
+        let config = ClientConfig::new(addr, psk, "RU");
+        assert_eq!(config.country_code, "RU");
+    }
+
+    #[test]
+    fn test_sni_selection() {
+        let addr: SocketAddr = "127.0.0.1:8443".parse().unwrap();
+        let config = ClientConfig::new(addr, [0u8; 32], "RU");
+        let client = OstpClient::new(config);
+        
+        let sni = client.suggested_sni();
+        assert!(sni.is_some());
+        // Should be one of the Russian domains
+        let sni = sni.unwrap();
+        assert!(sni.ends_with(".ru"));
+    }
+}
--- a/ostp/src/crypto.rs
+++ b/ostp/src/crypto.rs
@@ -0,0 +1,149 @@
+//! OSTP Crypto Module - PSK, X25519, ChaCha20-Poly1305
+
+use chacha20poly1305::{
+    aead::{Aead, KeyInit, OsRng},
+    ChaCha20Poly1305, Nonce,
+};
+use hmac::{digest::KeyInit as HmacKeyInit, Hmac, Mac};
+use sha2::Sha256;
+use x25519_dalek::{EphemeralSecret, PublicKey, SharedSecret};
+
+/// AEAD error type re-export
+pub type AeadError = chacha20poly1305::aead::Error;
+
+type HmacSha256 = Hmac<Sha256>;
+
+/// PSK-based silent handshake validator
+pub struct PskValidator {
+    psk: [u8; 32],
+}
+
+impl PskValidator {
+    pub fn new(psk: [u8; 32]) -> Self {
+        Self { psk }
+    }
+
+    /// Generate HMAC signature for packet authentication
+    pub fn sign(&self, data: &[u8]) -> [u8; 32] {
+        let mut mac: HmacSha256 = HmacKeyInit::new_from_slice(&self.psk).expect("HMAC key size");
+        mac.update(data);
+        mac.finalize().into_bytes().into()
+    }
+
+    /// Verify packet has valid PSK-derived signature (silent drop if invalid)
+    pub fn verify(&self, data: &[u8], signature: &[u8; 32]) -> bool {
+        let mut mac: HmacSha256 = HmacKeyInit::new_from_slice(&self.psk).expect("HMAC key size");
+        mac.update(data);
+        mac.verify_slice(signature).is_ok()
+    }
+}
+
+/// X25519 key exchange
+pub struct KeyExchange {
+    secret: EphemeralSecret,
+    public: PublicKey,
+}
+
+impl KeyExchange {
+    pub fn new() -> Self {
+        let secret = EphemeralSecret::random_from_rng(OsRng);
+        let public = PublicKey::from(&secret);
+        Self { secret, public }
+    }
+
+    pub fn public_key(&self) -> &PublicKey {
+        &self.public
+    }
+
+    pub fn derive_shared(self, peer_public: &PublicKey) -> SharedSecret {
+        self.secret.diffie_hellman(peer_public)
+    }
+}
+
+impl Default for KeyExchange {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// AEAD cipher for data encryption
+pub struct AeadCipher {
+    cipher: ChaCha20Poly1305,
+    nonce_counter: u64,
+}
+
+impl AeadCipher {
+    pub fn new(key: &[u8; 32]) -> Self {
+        let cipher = ChaCha20Poly1305::new_from_slice(key).expect("key size");
+        Self {
+            cipher,
+            nonce_counter: 0,
+        }
+    }
+
+    fn next_nonce(&mut self) -> Nonce {
+        let mut nonce = [0u8; 12];
+        nonce[4..12].copy_from_slice(&self.nonce_counter.to_le_bytes());
+        self.nonce_counter = self.nonce_counter.wrapping_add(1);
+        Nonce::from(nonce)
+    }
+
+    pub fn encrypt(&mut self, plaintext: &[u8]) -> Result<Vec<u8>, AeadError> {
+        let nonce = self.next_nonce();
+        let mut ciphertext = self.cipher.encrypt(&nonce, plaintext)?;
+        // Prepend nonce for decryption
+        let mut output = nonce.to_vec();
+        output.append(&mut ciphertext);
+        Ok(output)
+    }
+
+    pub fn decrypt(&self, ciphertext: &[u8]) -> Result<Vec<u8>, AeadError> {
+        if ciphertext.len() < 12 {
+            return Err(chacha20poly1305::aead::Error);
+        }
+        let nonce = Nonce::from_slice(&ciphertext[..12]);
+        self.cipher.decrypt(nonce, &ciphertext[12..])
+    }
+}
+
+/// Derive session key from shared secret using HKDF-like expansion
+pub fn derive_session_key(shared: &SharedSecret, salt: &[u8]) -> [u8; 32] {
+    let mut mac: HmacSha256 = HmacKeyInit::new_from_slice(salt).expect("HMAC key size");
+    mac.update(shared.as_bytes());
+    mac.finalize().into_bytes().into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_psk_sign_verify() {
+        let psk = [0x42u8; 32];
+        let validator = PskValidator::new(psk);
+        let data = b"hello";
+        let sig = validator.sign(data);
+        assert!(validator.verify(data, &sig));
+    }
+
+    #[test]
+    fn test_key_exchange() {
+        let alice = KeyExchange::new();
+        let bob = KeyExchange::new();
+        let alice_pub = *alice.public_key();
+        let bob_pub = *bob.public_key();
+        let alice_shared = alice.derive_shared(&bob_pub);
+        let bob_shared = bob.derive_shared(&alice_pub);
+        assert_eq!(alice_shared.as_bytes(), bob_shared.as_bytes());
+    }
+
+    #[test]
+    fn test_aead_encrypt_decrypt() {
+        let key = [0x11u8; 32];
+        let mut cipher = AeadCipher::new(&key);
+        let plaintext = b"secret message";
+        let ciphertext = cipher.encrypt(plaintext).unwrap();
+        let decrypted = cipher.decrypt(&ciphertext).unwrap();
+        assert_eq!(plaintext.as_slice(), decrypted.as_slice());
+    }
+}
--- a/ostp/src/lib.rs
+++ b/ostp/src/lib.rs
@@ -0,0 +1,11 @@
+pub mod client;
+pub mod crypto;
+pub mod mimicry;
+pub mod server;
+pub mod uot;
+
+pub use client::{ClientConfig, OstpClient};
+pub use crypto::{AeadCipher, KeyExchange, PskValidator};
+pub use mimicry::{MimicryEngine, TlsHelloBuilder};
+pub use server::{OstpServer, ServerConfig};
+pub use uot::{decode_frame, encode_frame, FrameFlags, Fragmenter, Reassembler};
--- a/ostp/src/mimicry.rs
+++ b/ostp/src/mimicry.rs
@@ -0,0 +1,174 @@
+//! Dynamic SNI & TLS Mimicry Engine
+
+use std::collections::HashMap;
+
+/// Geo-based SNI target selection
+pub struct MimicryEngine {
+    geo_sni_map: HashMap<String, Vec<String>>,
+}
+
+impl MimicryEngine {
+    pub fn new() -> Self {
+        let mut geo_sni_map = HashMap::new();
+
+        // Default geo-SNI mappings for contextual mimicry
+        geo_sni_map.insert(
+            "RU".into(),
+            vec![
+                "gosuslugi.ru".into(),
+                "sberbank.ru".into(),
+                "yandex.ru".into(),
+            ],
+        );
+        geo_sni_map.insert(
+            "NO".into(),
+            vec!["bankid.no".into(), "vipps.no".into(), "altinn.no".into()],
+        );
+        geo_sni_map.insert(
+            "DE".into(),
+            vec![
+                "sparkasse.de".into(),
+                "deutsche-bank.de".into(),
+                "bund.de".into(),
+            ],
+        );
+        geo_sni_map.insert(
+            "US".into(),
+            vec![
+                "apple.com".into(),
+                "microsoft.com".into(),
+                "amazon.com".into(),
+            ],
+        );
+        geo_sni_map.insert(
+            "CN".into(),
+            vec!["qq.com".into(), "baidu.com".into(), "taobao.com".into()],
+        );
+
+        Self { geo_sni_map }
+    }
+
+    /// Select SNI based on geo-location
+    pub fn select_sni(&self, country_code: &str) -> Option<&str> {
+        self.geo_sni_map
+            .get(country_code)
+            .and_then(|list| list.first().map(|s| s.as_str()))
+    }
+
+    /// Get random SNI from geo list for anti-fingerprinting
+    pub fn random_sni(&self, country_code: &str) -> Option<&str> {
+        self.geo_sni_map.get(country_code).and_then(|list| {
+            if list.is_empty() {
+                None
+            } else {
+                let idx = rand::random::<usize>() % list.len();
+                Some(list[idx].as_str())
+            }
+        })
+    }
+
+    /// Add custom geo-SNI mapping
+    pub fn add_mapping(&mut self, country: String, domains: Vec<String>) {
+        self.geo_sni_map.insert(country, domains);
+    }
+}
+
+impl Default for MimicryEngine {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// TLS ClientHello builder for REALITY-like mimicry
+pub struct TlsHelloBuilder {
+    sni: String,
+    random_session_id: bool,
+}
+
+impl TlsHelloBuilder {
+    pub fn new(sni: impl Into<String>) -> Self {
+        Self {
+            sni: sni.into(),
+            random_session_id: true,
+        }
+    }
+
+    /// Build minimal TLS 1.3 ClientHello-like header
+    pub fn build(&self) -> Vec<u8> {
+        let mut hello = Vec::with_capacity(256);
+
+        // TLS record header
+        hello.push(0x16); // Handshake
+        hello.extend_from_slice(&[0x03, 0x01]); // TLS 1.0 for compat
+
+        // Placeholder for length (will update)
+        let len_pos = hello.len();
+        hello.extend_from_slice(&[0x00, 0x00]);
+
+        // Handshake header
+        hello.push(0x01); // ClientHello
+        let hs_len_pos = hello.len();
+        hello.extend_from_slice(&[0x00, 0x00, 0x00]); // length placeholder
+
+        // Client version (TLS 1.2 presented, 1.3 in extensions)
+        hello.extend_from_slice(&[0x03, 0x03]);
+
+        // Random (32 bytes)
+        let random: [u8; 32] = rand::random();
+        hello.extend_from_slice(&random);
+
+        // Session ID (32 bytes if random)
+        if self.random_session_id {
+            hello.push(32);
+            let session_id: [u8; 32] = rand::random();
+            hello.extend_from_slice(&session_id);
+        } else {
+            hello.push(0);
+        }
+
+        // Cipher suites (TLS 1.3 suites)
+        hello.extend_from_slice(&[0x00, 0x06]); // 3 suites
+        hello.extend_from_slice(&[0x13, 0x01]); // TLS_AES_128_GCM_SHA256
+        hello.extend_from_slice(&[0x13, 0x02]); // TLS_AES_256_GCM_SHA384
+        hello.extend_from_slice(&[0x13, 0x03]); // TLS_CHACHA20_POLY1305_SHA256
+
+        // Compression (null)
+        hello.extend_from_slice(&[0x01, 0x00]);
+
+        // Extensions with SNI
+        let ext_start = hello.len();
+        hello.extend_from_slice(&[0x00, 0x00]); // ext length placeholder
+
+        // SNI extension
+        hello.extend_from_slice(&[0x00, 0x00]); // type: server_name
+        let sni_bytes = self.sni.as_bytes();
+        let sni_ext_len = sni_bytes.len() + 5;
+        hello.extend_from_slice(&(sni_ext_len as u16).to_be_bytes());
+        hello.extend_from_slice(&((sni_bytes.len() + 3) as u16).to_be_bytes());
+        hello.push(0x00); // host_name type
+        hello.extend_from_slice(&(sni_bytes.len() as u16).to_be_bytes());
+        hello.extend_from_slice(sni_bytes);
+
+        // supported_versions extension
+        hello.extend_from_slice(&[0x00, 0x2b]); // type
+        hello.extend_from_slice(&[0x00, 0x03]); // length
+        hello.push(0x02); // versions length
+        hello.extend_from_slice(&[0x03, 0x04]); // TLS 1.3
+
+        // Update lengths
+        let ext_len = hello.len() - ext_start - 2;
+        hello[ext_start] = (ext_len >> 8) as u8;
+        hello[ext_start + 1] = ext_len as u8;
+
+        let total_len = hello.len() - 5;
+        hello[len_pos] = (total_len >> 8) as u8;
+        hello[len_pos + 1] = total_len as u8;
+
+        let hs_len = hello.len() - hs_len_pos - 3;
+        hello[hs_len_pos] = 0;
+        hello[hs_len_pos + 1] = (hs_len >> 8) as u8;
+        hello[hs_len_pos + 2] = hs_len as u8;
+
+        hello
+    }
+}
--- a/ostp/src/server.rs
+++ b/ostp/src/server.rs
@@ -0,0 +1,192 @@
+//! OSTP Server - Stealth relay endpoint
+
+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::{TcpListener, TcpStream};
+use tokio::sync::RwLock;
+
+use crate::crypto::{AeadCipher, KeyExchange, PskValidator};
+use crate::uot::decode_frame;
+use bytes::BytesMut;
+
+/// Server configuration
+#[derive(Clone)]
+pub struct ServerConfig {
+    pub listen_addr: SocketAddr,
+    pub psk: [u8; 32],
+    pub max_connections: usize,
+}
+
+impl ServerConfig {
+    pub fn new(addr: SocketAddr, psk: [u8; 32]) -> Self {
+        Self {
+            listen_addr: addr,
+            psk,
+            max_connections: 1024,
+        }
+    }
+}
+
+/// Active connection state
+#[allow(dead_code)]
+struct Connection {
+    cipher: AeadCipher,
+    user_id: Option<uuid::Uuid>,
+    bytes_rx: u64,
+    bytes_tx: u64,
+}
+
+/// OSTP Server with silent handshake
+pub struct OstpServer {
+    config: ServerConfig,
+    #[allow(dead_code)]
+    psk_validator: PskValidator,
+    connections: Arc<RwLock<HashMap<SocketAddr, Connection>>>,
+}
+
+impl OstpServer {
+    pub fn new(config: ServerConfig) -> Self {
+        let psk_validator = PskValidator::new(config.psk);
+        Self {
+            config,
+            psk_validator,
+            connections: Arc::new(RwLock::new(HashMap::new())),
+        }
+    }
+
+    /// Start the server (main async loop)
+    pub async fn run(&self) -> anyhow::Result<()> {
+        let listener = TcpListener::bind(self.config.listen_addr).await?;
+        tracing::info!("OSTP server listening on {}", self.config.listen_addr);
+
+        loop {
+            match listener.accept().await {
+                Ok((stream, addr)) => {
+                    let psk_validator = PskValidator::new(self.config.psk);
+                    let connections = Arc::clone(&self.connections);
+                    
+                    tokio::spawn(async move {
+                        if let Err(e) = Self::handle_connection(stream, addr, psk_validator, connections).await {
+                            tracing::debug!("Connection {} closed: {}", addr, e);
+                        }
+                    });
+                }
+                Err(e) => {
+                    tracing::warn!("Accept error: {}", e);
+                }
+            }
+        }
+    }
+
+    async fn handle_connection(
+        mut stream: TcpStream,
+        addr: SocketAddr,
+        psk_validator: PskValidator,
+        connections: Arc<RwLock<HashMap<SocketAddr, Connection>>>,
+    ) -> anyhow::Result<()> {
+        let mut buf = [0u8; 4096];
+        
+        // Phase 1: Silent PSK handshake (32-byte signature must be first)
+        let n = stream.read(&mut buf).await?;
+        if n < 64 {
+            // Silent drop - don't reveal port is open
+            return Ok(());
+        }
+
+        let signature: [u8; 32] = buf[..32].try_into()?;
+        let payload = &buf[32..n];
+
+        if !psk_validator.verify(payload, &signature) {
+            // Silent drop on invalid PSK - core anti-probing defense
+            tracing::trace!("Silent drop for {}: invalid PSK", addr);
+            return Ok(());
+        }
+
+        // Phase 2: X25519 key exchange
+        // Payload contains client's public key (32 bytes)
+        if payload.len() < 32 {
+            return Ok(());
+        }
+        
+        let client_pubkey_bytes: [u8; 32] = payload[..32].try_into()?;
+        let client_pubkey = x25519_dalek::PublicKey::from(client_pubkey_bytes);
+        
+        let server_kex = KeyExchange::new();
+        let server_pubkey = *server_kex.public_key();
+        let shared_secret = server_kex.derive_shared(&client_pubkey);
+        
+        // Derive session key
+        let session_key = crate::crypto::derive_session_key(&shared_secret, b"ostp-session-v1");
+        let cipher = AeadCipher::new(&session_key);
+
+        // Send server's public key (signed with PSK)
+        let server_response = server_pubkey.as_bytes();
+        let response_sig = psk_validator.sign(server_response);
+        stream.write_all(&response_sig).await?;
+        stream.write_all(server_response).await?;
+
+        // Store connection
+        {
+            let mut conns = connections.write().await;
+            conns.insert(addr, Connection {
+                cipher,
+                user_id: None,
+                bytes_rx: 0,
+                bytes_tx: 0,
+            });
+        }
+
+        tracing::info!("Session established with {}", addr);
+
+        // Phase 3: Encrypted relay loop
+        let mut read_buf = BytesMut::with_capacity(65536);
+        
+        loop {
+            let n = stream.read(&mut buf).await?;
+            if n == 0 {
+                break;
+            }
+
+            read_buf.extend_from_slice(&buf[..n]);
+
+            // Process frames
+            while let Some((data, flags)) = decode_frame(&mut read_buf)? {
+                let conns = connections.read().await;
+                if let Some(conn) = conns.get(&addr) {
+                    match conn.cipher.decrypt(&data) {
+                        Ok(plaintext) => {
+                            if flags.is_data() {
+                                // TODO: Route decrypted data to destination
+                                tracing::trace!("Received {} bytes from {}", plaintext.len(), addr);
+                            }
+                        }
+                        Err(_) => {
+                            tracing::warn!("Decrypt failed for {}", addr);
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        // Cleanup
+        connections.write().await.remove(&addr);
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_server_config() {
+        let addr: SocketAddr = "127.0.0.1:8443".parse().unwrap();
+        let psk = [0x42u8; 32];
+        let config = ServerConfig::new(addr, psk);
+        assert_eq!(config.listen_addr, addr);
+        assert_eq!(config.max_connections, 1024);
+    }
+}
--- a/ostp/src/uot.rs
+++ b/ostp/src/uot.rs
@@ -0,0 +1,132 @@
+//! UoT (UDP-over-TCP) framing layer
+
+use bytes::{Buf, BufMut, Bytes, BytesMut};
+use thiserror::Error;
+
+/// Maximum UDP datagram size
+pub const MAX_UDP_SIZE: usize = 65535;
+/// Frame header: 2 bytes length + 1 byte flags
+const HEADER_SIZE: usize = 3;
+
+#[derive(Error, Debug)]
+pub enum FrameError {
+    #[error("frame too large: {0} bytes")]
+    TooLarge(usize),
+    #[error("incomplete frame")]
+    Incomplete,
+    #[error("invalid frame")]
+    Invalid,
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct FrameFlags(u8);
+
+impl FrameFlags {
+    pub const DATA: Self = Self(0x00);
+    pub const CONTROL: Self = Self(0x01);
+    pub const PADDING: Self = Self(0x02);
+
+    pub fn is_data(self) -> bool {
+        self.0 == 0x00
+    }
+}
+
+/// Encapsulate UDP datagram into framed format with random padding
+pub fn encode_frame(data: &[u8], flags: FrameFlags, padding: usize) -> Result<Bytes, FrameError> {
+    let total_len = data.len() + padding;
+    if total_len > MAX_UDP_SIZE {
+        return Err(FrameError::TooLarge(total_len));
+    }
+
+    let mut buf = BytesMut::with_capacity(HEADER_SIZE + total_len);
+    buf.put_u16(total_len as u16);
+    buf.put_u8(flags.0);
+    buf.put_slice(data);
+
+    // Random padding to avoid fingerprinting
+    if padding > 0 {
+        let pad: Vec<u8> = (0..padding).map(|_| rand::random()).collect();
+        buf.put_slice(&pad);
+    }
+
+    Ok(buf.freeze())
+}
+
+/// Decode frame from buffer, returns (payload, data_length, flags)
+pub fn decode_frame(buf: &mut BytesMut) -> Result<Option<(Bytes, FrameFlags)>, FrameError> {
+    if buf.len() < HEADER_SIZE {
+        return Ok(None);
+    }
+
+    let len = u16::from_be_bytes([buf[0], buf[1]]) as usize;
+    let flags = FrameFlags(buf[2]);
+
+    if buf.len() < HEADER_SIZE + len {
+        return Ok(None);
+    }
+
+    buf.advance(HEADER_SIZE);
+    let data = buf.split_to(len).freeze();
+
+    Ok(Some((data, flags)))
+}
+
+/// MTU-aware fragmentation
+pub struct Fragmenter {
+    mtu: usize,
+}
+
+impl Fragmenter {
+    pub fn new(mtu: usize) -> Self {
+        Self { mtu }
+    }
+
+    pub fn fragment(&self, data: &[u8]) -> Vec<Bytes> {
+        data.chunks(self.mtu)
+            .map(|chunk| Bytes::copy_from_slice(chunk))
+            .collect()
+    }
+}
+
+/// Reassembly buffer for fragmented packets
+pub struct Reassembler {
+    buffer: BytesMut,
+    expected_len: Option<usize>,
+}
+
+impl Reassembler {
+    pub fn new() -> Self {
+        Self {
+            buffer: BytesMut::new(),
+            expected_len: None,
+        }
+    }
+
+    pub fn push(&mut self, fragment: &[u8], total_len: usize) {
+        if self.expected_len.is_none() {
+            self.expected_len = Some(total_len);
+        }
+        self.buffer.extend_from_slice(fragment);
+    }
+
+    pub fn is_complete(&self) -> bool {
+        self.expected_len
+            .map(|len| self.buffer.len() >= len)
+            .unwrap_or(false)
+    }
+
+    pub fn take(&mut self) -> Option<Bytes> {
+        if self.is_complete() {
+            self.expected_len = None;
+            Some(self.buffer.split().freeze())
+        } else {
+            None
+        }
+    }
+}
+
+impl Default for Reassembler {
+    fn default() -> Self {
+        Self::new()
+    }
+}