Encryption Layers

KayakNet uses multiple layers of encryption to protect your data.

Overview

┌─────────────────────────────────────────────────┐
│  Layer 4: Application E2E Encryption            │
│  (Chat messages, delivery info, etc.)           │
├─────────────────────────────────────────────────┤
│  Layer 3: Onion Routing Encryption              │
│  (3 nested layers, one per hop)                 │
├─────────────────────────────────────────────────┤
│  Layer 2: Transport Encryption (TLS 1.3)        │
│  (Per-connection encryption)                    │
├─────────────────────────────────────────────────┤
│  Layer 1: Physical Transport                    │
│  (TCP/UDP packets)                              │
└─────────────────────────────────────────────────┘

Layer 1: Transport Encryption

Every connection between nodes uses TLS 1.3:

• Cipher Suite: TLS_CHACHA20_POLY1305_SHA256

• Key Exchange: X25519

• Certificate: Self-signed Ed25519

What It Protects

• Content of packets between directly connected peers

• Node identity (certificate includes public key)

What It Doesn't Protect

• Traffic patterns (timing, size)

• Metadata (who's talking to whom)

Layer 2: Onion Routing

Messages are wrapped in 3 layers of encryption:

Sender encrypts:
  Layer 3 key → for Exit Node
    Layer 2 key → for Middle Node
      Layer 1 key → for Entry Node
        Message

Key Exchange

Each hop gets its own ephemeral key:

1. Sender generates X25519 keypair

2. ECDH with hop's public key

3. HKDF to derive symmetric key

4. ChaCha20-Poly1305 encryption

Header Format

┌──────────────────────────────────┐
│ Ephemeral Public Key (32 bytes)  │
├──────────────────────────────────┤
│ Next Hop (encrypted)             │
├──────────────────────────────────┤
│ Payload (encrypted)              │
└──────────────────────────────────┘

Layer 3: Application E2E

Chat messages and sensitive data have additional encryption:

Chat Room Keys

• Symmetric key shared by room members

• Rotated when membership changes

• ChaCha20-Poly1305

Direct Messages

• X25519 key exchange with recipient

• Per-message key derivation (forward secrecy)

• Ed25519 signature for authentication

Escrow Data

• Delivery info encrypted to seller's key

• Only seller can decrypt

Cryptographic Primitives

Purpose	Algorithm	Standard
Signatures	Ed25519	RFC 8032
Key Exchange	X25519	RFC 7748
Symmetric Encryption	ChaCha20-Poly1305	RFC 8439
Key Derivation	HKDF-SHA256	RFC 5869
Hashing	BLAKE2b-256	RFC 7693

Key Management

Node Identity Key

• Ed25519 keypair

• Generated on first run

• Stored in identity.key

• Never transmitted

Session Keys

• Ephemeral per-connection

• X25519 exchange

• Destroyed after use

Room Keys

• Generated by room creator

• Encrypted to each member

• Rotated on membership change

Forward Secrecy

KayakNet provides forward secrecy through:

1. Ephemeral Keys - New keys per session

2. Key Rotation - Regular key changes

3. Key Destruction - Old keys deleted

If your long-term key is compromised:

• Past messages remain encrypted

• Only future messages affected

Quantum Resistance

Current algorithms are NOT quantum-resistant. Planned upgrades:

• CRYSTALS-Kyber - Post-quantum key exchange

• CRYSTALS-Dilithium - Post-quantum signatures

• Hybrid Mode - Classical + PQ for transition

Implementation Details

Random Number Generation

// Using crypto/rand for all randomness
import "crypto/rand"

key := make([]byte, 32)
rand.Read(key)

Constant-Time Operations

All cryptographic comparisons use constant-time functions:

import "crypto/subtle"

if subtle.ConstantTimeCompare(a, b) == 1 {
    // Equal
}

Memory Security

Sensitive data is:

• Zeroed after use

• Not logged or printed

• Stored in secure memory where possible

Verification

You can verify encryption using packet captures:

# Capture KayakNet traffic
tcpdump -i any port 4242 -w capture.pcap

# Analyze with Wireshark
# All payloads should appear as random data