# VCL Protocol
**Verified Commit Link** — Cryptographically chained packet transport protocol
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## 📚 Documentation
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[](https://www.rust-lang.org)
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[](LICENSE)
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## 📖 About
VCL Protocol is a transport protocol where each packet cryptographically links to the previous one, creating an immutable chain of data transmission. Inspired by blockchain principles, optimized for real-time networking.
**Now with X25519 Handshake + XChaCha20-Poly1305 Encryption + Replay Protection** — secure key exchange, authenticated encryption, and protection against packet replay attacks!
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## ✨ Features
| 🔐 Cryptographic Chain | Each packet references hash of previous packet |
| ✍️ Ed25519 Signatures | Fast and secure digital signatures |
| 🔑 X25519 Handshake | Ephemeral key exchange, no pre-shared keys needed |
| 🔒 XChaCha20-Poly1305 | Authenticated encryption for all payloads |
| 🛡️ Replay Protection | Sequence number + nonce tracking prevents packet replay |
| ✅ Chain Validation | Automatic integrity checking |
| ⚡ UDP Transport | Low latency, high performance |
| 🧪 Full Test Suite | 14 passing tests (unit + integration) |
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## 🏗️ Architecture
Packet N Packet N+1 Packet N+2
+--------+ +--------+ +--------+
| hash | | prev | | prev |
| 0x00.. | --> | 0x00.. | --> | 0x3a.. |
| sig | | sig | | sig |
+--------+ +--------+ +--------+
hash(Packet N) -> stored in prev_hash of Packet N+1
hash(Packet N+1) -> stored in prev_hash of Packet N+2
### Handshake Flow
Client Server
| |
| -- ClientHello (pubkey) ----> |
| |
| <---- ServerHello (pubkey) -- |
| |
| [Shared secret computed] |
| [Secure channel established] |
### Encryption Flow
Send: plaintext → encrypt(XChaCha20) → sign(Ed25519) → send
Recv: receive → verify(Ed25519) → decrypt(XChaCha20) → plaintext
### Replay Protection
1. Check sequence number (must be > last received)
2. Check nonce (must not be in seen_nonces set)
3. Store nonce in sliding window (1000 entries)
4. Reject packet if either check fails
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## 🚀 Quick Start
### Installation
# Install Rust (if not already installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Clone repository
git clone https://github.com/ultrakill148852-collab/vcl-protocol.git
cd vcl-protocol
### Run Demo
cargo run
### Run Tests
cargo test
### Expected Output (Demo)
=== VCL Protocol Demo ===
Server started on 127.0.0.1:8080
Handshake completed
Client connected (handshake complete)
Client sent: Message 1
Server received packet 1: Message 1
Client sent: Message 2
Server received packet 2: Message 2
Client sent: Message 3
Server received packet 3: Message 3
Client sent: Message 4
Server received packet 4: Message 4
Client sent: Message 5
Server received packet 5: Message 5
=== Demo Complete ===
### Expected Output (Tests)
running 10 tests
test crypto::tests::test_hash_data ... ok
test crypto::tests::test_decrypt_wrong_key_fails ... ok
...
test result: ok. 10 passed; 0 failed
running 4 tests
test test_client_server_basic ... ok
test test_encryption_integrity ... ok
test test_chain_validation ... ok
test test_replay_protection ... ok
test result: ok. 4 passed; 0 failed
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## 📦 Packet Structure
pub struct VCLPacket {
pub version: u8, // Protocol version
pub sequence: u64, // Packet sequence number (monotonic)
pub prev_hash: Vec<u8>, // SHA-256 hash of previous packet
pub nonce: [u8; 24], // XChaCha20 nonce for encryption
pub payload: Vec<u8>, // Encrypted data payload
pub signature: Vec<u8>, // Ed25519 signature
}
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## 🎯 Use Cases
### 💰 Financial Transactions
Immutable audit log of all transactions with cryptographic proof of integrity.
### 🎮 Anti-Cheat Systems
Verify integrity of game events and detect tampering in real-time.
### 📋 Audit Logging
Cryptographically proven data integrity for compliance and debugging.
### 🔐 Secure Communications
Authenticated and encrypted channel with end-to-end verification, ephemeral key exchange, and replay protection.
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## 🔬 Technical Details
### Cryptography
- **Hashing:** SHA-256
- **Signatures:** Ed25519 (Edwards-curve Digital Signature Algorithm)
- **Key Exchange:** X25519 (Elliptic-curve Diffie-Hellman)
- **Encryption:** XChaCha20-Poly1305 (AEAD)
- **Key Generation:** CSPRNG (Cryptographically Secure PRNG)
- **Replay Protection:** Sequence number validation + nonce tracking (1000-entry window)
### Transport
- **Protocol:** UDP
- **Runtime:** Tokio async
- **Max Packet Size:** 65535 bytes
### Serialization
- **Format:** Bincode
- **Efficiency:** Minimal overhead, fast serialization
### Dependencies
- `ed25519-dalek` — Ed25519 signatures
- `x25519-dalek` — X25519 key exchange
- `chacha20poly1305` — XChaCha20-Poly1305 AEAD encryption
- `sha2` — SHA-256 hashing
- `tokio` — Async runtime
- `serde` + `bincode` — Serialization
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## 🛠️ Development
# Run all tests
cargo test
# Run unit tests only
cargo test --lib
# Run integration tests only
cargo test --test integration_test
# Format code
cargo fmt
# Linting
cargo clippy
# Build release
cargo build --release
# Generate docs
cargo doc --open
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## 📄 License
MIT License — see [LICENSE](LICENSE) file for details.
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## 👤 Author
**ultrakill148852-collab** — Creator of the VCL Protocol
GitHub: [@ultrakill148852-collab](https://github.com/ultrakill148852-collab)
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## 🙏 Acknowledgments
- **Ed25519** — Fast and secure cryptography
- **X25519** — Efficient elliptic-curve key exchange
- **XChaCha20-Poly1305** — Modern authenticated encryption
- **Tokio** — Asynchronous runtime for Rust
- **Rust** — The language that makes the impossible possible
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<div align="center">
**Made with ❤️ using Rust**
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