GPTL - General Purpose Transport Layer

A next-generation anonymity network with comprehensive defenses against modern attacks on Tor, I2P, and VPN systems.

Overview

GPTL implements cutting-edge countermeasures against 10 major attack categories identified in academic research from 2005-2024:

1. Traffic Confirmation Attacks (Murdoch-Danezis, 2005)
2. Website Fingerprinting (Panchenko et al., 2011-2016)
3. Circuit Fingerprinting (Kwon et al., 2015)
4. Guard Discovery Attacks (Overlier-Syverson, 2006)
5. Sniper Attacks (Resource Exhaustion) (Jansen et al., 2014)
6. Sybil Attacks (Biryukov et al., 2013)
7. BGP Hijacking Attacks (RAPTOR) (Sun et al., 2015)
8. Timing Attacks
9. DNS Leakage
10. WebRTC Leakage

Architecture

┌─────────────────────────────────────────────────────────────┐
│                    APPLICATION LAYER                        │
│  - WebRTC Guard    - DNS Guard    - Protocol Hardening      │
├─────────────────────────────────────────────────────────────┤
│                    CIRCUIT LAYER                            │
│  - Circuit Shield  - Vanguards    - Guard Armor             │
├─────────────────────────────────────────────────────────────┤
│                    ROUTING LAYER                            │
│  - BGP Guard       - AS-Aware Selection    - Multi-Path     │
├─────────────────────────────────────────────────────────────┤
│                    TRANSPORT LAYER                          │
│  - Timing Shield   - Traffic Shaping    - Adaptive Padding  │
├─────────────────────────────────────────────────────────────┤
│                    RESOURCE LAYER                           │
│  - Resource Guard  - Sybil Shield    - Rate Limiting        │
└─────────────────────────────────────────────────────────────┘

Quick Start

Prerequisites

• Rust 1.75+
• Cargo

Building

cd rust
cargo build --release

Running Tests

cd rust
cargo test

CLI Usage

The gptl binary is the primary way to configure GPTL. Configuration is stored at ~/.config/gptl/config.toml (Unix) or %APPDATA%\gptl\config.toml (Windows).

Commands

gptl status                              # Overview: level badge + all 11 protections
gptl config show                         # Full configuration table
gptl config show --format json           # Machine-readable JSON
gptl config set <key> <value>            # Change a setting (security changes require confirmation)
gptl config keys                         # All settable keys with accepted values
gptl config reset                        # Reset to defaults
gptl config path                         # Show config file location

gptl security level standard|enhanced|maximum   # Change security level (shows full diff + confirms)
gptl security level enhanced --label-only        # Update label only, keep individual settings
gptl security status                             # Protection checklist
gptl security audit                              # Detect mismatches and weaknesses

gptl profile list                        # List profiles (built-ins: standard/enhanced/maximum)
gptl profile show <name>                 # Preview a profile
gptl profile apply <name>                # Apply profile (shows diff + confirmation)
gptl profile save <name>                 # Save current config as named profile
gptl profile delete <name>               # Delete a saved profile

# Skip confirmation prompts (for scripting):
gptl -y security level maximum
gptl --yes profile apply standard

Security-sensitive changes (disabling protections, lowering security level) always show a diff of what will change and ask for confirmation. Use -y/--yes to bypass in scripts.

Security Levels

GPTL provides three configurable security levels:

Standard

• Basic traffic padding
• DNS-over-HTTPS protection
• WebRTC leak prevention
• Suitable for: General browsing

Enhanced (Default)

• All Standard features
• Timing protection with jitter
• Circuit obfuscation
• Vanguard layered guards
• Defends against: Traffic analysis, circuit fingerprinting

Maximum

• All Enhanced features
• BGP-aware routing
• Multi-path traffic splitting
• Aggressive padding and obfuscation
• Suitable for: High-risk situations, activists, journalists

Module Structure

gptl-core

Core anti-surveillance protections:

• anti_surveillance/traffic_shaping.rs - Traffic confirmation attack defense
• anti_surveillance/padding.rs - Website fingerprinting defense (WTF-PAD)
• anti_surveillance/timing_protection.rs - Timing attack defense
• anti_surveillance/circuit_obfuscation.rs - Circuit fingerprinting defense
• anti_surveillance/flow_correlation_defense.rs - DeepCorr defense

gptl-routing

Secure routing and network-level protections:

• bgp_protection.rs - RAPTOR/BGP hijacking defense with RPKI validation
• guard_management.rs - Vanguard protection against guard discovery
• resource_protection.rs - Sniper attack defense with PoW
• dns_protection.rs - DNS leak prevention with DoH/DoT
• webrtc_protection.rs - WebRTC leak prevention
• sybil_defense.rs - Sybil attack detection and prevention
• circuit/ - Circuit pool, health monitoring, and rotation

gptl-crypto

Production-grade cryptographic primitives (FIPS 140-3 validated via aws-lc-rs):

• AEAD ciphers — AES-256-GCM (primary), ChaCha20-Poly1305 (fallback)
• Key exchange — X25519 and Hybrid X25519 + ML-KEM-768 (post-quantum, NIST FIPS 203)
• Forward secrecy — Key ratcheting with Double Ratchet-inspired design
• Counter-based nonces — NIST-compliant with automatic rotation at 2³² messages
• Memory safety — All keys and secrets zeroized on drop

gptl-cli

User-facing command-line interface (gptl binary):

• main.rs — Entry point; dispatches config, security, profile, and status subcommands
• Config stored at ~/.config/gptl/config.toml (Unix) / %APPDATA%\gptl\config.toml (Windows)
• Built-in profiles: standard, enhanced, maximum (read-only)
• User profiles: ~/.config/gptl/profiles/<name>.toml
• Security-sensitive changes require confirmation; use -y/--yes for scripting

gptl-relay

Enterprise relay server with multi-layer security:

• auth/ — Multi-factor authentication (password, TOTP, WebAuthn, mTLS)
• ip_restriction/ — IP allowlist, geolocation blocking, threat intelligence
• rate_limit/ — Token bucket limiting with CAPTCHA integration
• session/ — JWT-based session management with binding
• api_key/ — Scoped API key management with HMAC validation
• audit/ — Tamper-evident audit log with Merkle tree integrity
• auto_setup.rs — Cross-platform firewall automation (UFW/iptables/nftables, netsh, pfctl)

Research Documentation

See research/TOR_I2P_VPN_ATTACKS_RESEARCH_REPORT.md for comprehensive analysis of each attack category including:

• Attack mechanisms and effectiveness
• Historical context and evolution
• Academic references
• GPTL countermeasure design rationale

Key Features

1. Traffic Confirmation Defense

• Constant-rate cell transmission
• Multi-path routing
• Cover traffic generation
• Congestion-independent timing

2. Website Fingerprinting Defense

• WTF-PAD adaptive padding
• Burst morphing
• Standardized traffic patterns
• Game-theoretic optimization

3. Circuit Fingerprinting Defense

• Preemptive circuit padding (PCP)
• Vanguard layered guards
• Circuit type obfuscation
• Standardized cell sequences with random payloads (indistinguishable from real data)

4. Guard Discovery Defense

• 3-layer guard architecture
• Predecessor attack detection
• DoS-resistant rotation
• Reputation-based selection

5. Sniper Attack Defense

• Proof-of-work circuit allocation
• Memory pool management
• Window-based flow control
• Circuit prioritization

6. Sybil Defense

• Economic stake requirements
• Reputation system
• Behavioral pattern detection
• Bandwidth verification
• Trust networks

7. BGP Hijacking Defense

• RPKI route validation
• AS-aware path selection (intermediate-hop diversity)
• Real-time hijack detection
• Counter-RAPTOR selection

8. Timing Attack Defense

• Poisson-distributed jitter
• Packet batching and reordering
• Clock skew protection
• Watermark detection

9. DNS Leak Prevention

• DNS-over-HTTPS (DoH)
• DNS-over-TLS (DoT)
• Transparent proxy detection
• System DNS management

10. WebRTC Leak Prevention

• ICE candidate filtering
• TURN relay enforcement
• Browser policy enforcement
• Leak testing

Cryptography

GPTL uses production-grade cryptographic primitives:

Primitive	Algorithm	Standard
Symmetric encryption	AES-256-GCM	NIST FIPS 197
Symmetric fallback	ChaCha20-Poly1305	RFC 8439
Classic key exchange	X25519	RFC 7748
Post-quantum KEM	ML-KEM-768 (Kyber)	NIST FIPS 203
Hybrid key exchange	X25519 + ML-KEM-768	IETF draft-ietf-tls-ecdhe-mlkem
Forward secrecy	Double Ratchet	Signal specification
Crypto library	aws-lc-rs	FIPS 140-3 validated

Key properties:

• All keys and secrets are memory-zeroized on drop (zeroize crate)
• Constant-time operations for sensitive comparisons (subtle crate)
• Counter-based nonces with automatic rotation at 2³² messages
• Hybrid KEM provides both classical and post-quantum security

Configuration

use gptl_core::anti_surveillance::{AntiSurveillanceManager, SecurityLevel};
use gptl_routing::RoutingManager;

#[tokio::main]
async fn main() {
    // Configure security level
    let mut manager = AntiSurveillanceManager::new(Default::default());
    manager.set_security_level(SecurityLevel::Maximum).await;

    // Initialize protections
    manager.initialize().await.unwrap();

    // Process cells securely
    let protected_cells = manager.protect_outgoing(cell).await.unwrap();
}

Testing

Each module includes comprehensive unit tests:

# Run all tests
cd rust && cargo test

# Run with logging
RUST_LOG=debug cargo test -- --nocapture

# Run specific module tests
cargo test -p gptl-crypto
cargo test -p gptl-core
cargo test timing_protection
cargo test sybil_defense

Security Considerations

Current Limitations

• Requires integration with a transport layer for full deployment
• Network-level consensus and directory authority system not included
• Performance optimizations for high-throughput scenarios are ongoing

Security Properties

• Memory safety: Rust ownership model eliminates use-after-free and buffer overflows
• Cryptographic agility: Hybrid classical + post-quantum key exchange
• Forward secrecy: Double Ratchet ratcheting ensures past sessions remain secure
• Bounded resource usage: All data structures have growth limits to prevent DoS
• Tamper-evident logging: Merkle tree-backed audit log with cryptographic integrity

Contributing

This project is part of the GPTL security research initiative. See individual module documentation for contribution guidelines.

License

Licensed under either of:

• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)

at your option.

Acknowledgments

This implementation is based on research by:

• Murdoch & Danezis (2005) - Traffic confirmation attacks
• Panchenko et al. (2011, 2016) - Website fingerprinting
• Kwon et al. (2015) - Circuit fingerprinting attacks
• Overlier & Syverson (2006) - Guard discovery
• Jansen et al. (2014) - Sniper attacks
• Sun et al. (2015) - RAPTOR attacks
• Biryukov et al. (2013) - Sybil attacks

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Note: This is a security research implementation. Production deployment requires additional operational hardening and network infrastructure.