# Security Audit Preparation Documentation
This document provides comprehensive information for security auditors reviewing `chie-crypto`.
## Executive Summary
**chie-crypto** is a cryptographic library for the CHIE (Collective Hybrid Intelligence Ecosystem) protocol, providing essential cryptographic primitives and advanced features for secure content distribution.
- **Version**: 0.1.0
- **Language**: Rust (Edition 2024, MSRV 1.83)
- **License**: See LICENSE file
- **Lines of Code**: ~80 modules, 970 unit tests, 44 integration tests
- **Test Coverage**: 100% pass rate, zero warnings
## Audit Scope
### Core Cryptographic Primitives
1. **Symmetric Encryption** (`encryption.rs`)
- ChaCha20-Poly1305 AEAD
- Nonce handling and validation
- Authentication tag verification (constant-time)
2. **Digital Signatures** (`signing.rs`)
- Ed25519 signature generation and verification
- Batch verification
- Dual signature verification for bandwidth proofs
3. **Hashing** (`hash.rs`)
- BLAKE3 cryptographic hash function
- Incremental hashing for large files
- Hash-based commitments
4. **Key Derivation** (`kdf.rs`)
- HKDF (HMAC-based KDF) with SHA-256
- Content key derivation from master keys
- Salt handling
5. **Key Exchange** (`keyexchange.rs`)
- X25519 Diffie-Hellman
- Ephemeral and static keys
- Shared secret derivation
### Advanced Cryptographic Features
6. **Verifiable Random Functions** (`vrf.rs`)
- Ed25519-based VRF
- Challenge generation for bandwidth proofs
7. **Secret Sharing** (`shamir.rs`)
- Shamir's Secret Sharing over GF(256)
- Key backup and recovery
8. **Commitments** (`pedersen.rs`, `commitment.rs`)
- Pedersen commitments (homomorphic)
- Hash-based commitments
- Bandwidth proof commitments
9. **Merkle Trees** (`merkle.rs`)
- Binary Merkle trees
- Proof generation and verification
- Multi-proof support
10. **Threshold Cryptography** (`threshold.rs`, `dkg.rs`)
- Multi-signature aggregation
- Distributed key generation
- Threshold signatures
### Security Features
11. **Constant-Time Operations** (`ct.rs`)
- Constant-time comparison
- Timing side-channel resistance
12. **Key Management** (`rotation.rs`, `key_policy.rs`, `keystore.rs`)
- Automated key rotation
- Policy-based access control
- Secure key storage
13. **Side-Channel Resistance** (`sidechannel.rs`, `cache_timing.rs`)
- Timing attack detection
- Cache-timing mitigations
- Statistical analysis
14. **Entropy Quality** (`entropy.rs`)
- Entropy source monitoring
- Statistical health tests (NIST SP 800-90B)
15. **Audit and Compliance** (`audit_log.rs`, `compliance.rs`)
- Cryptographic operation logging
- FIPS 140-3 compliance reporting
## Security Properties
### Confidentiality
- ChaCha20-Poly1305 provides authenticated encryption
- X25519 provides forward-secret key exchange
- Secret sharing provides information-theoretic security
### Integrity
- Poly1305 authentication tags
- Ed25519 digital signatures
- Merkle tree proofs
### Authenticity
- Ed25519 signatures for message authentication
- VRF for verifiable randomness
- Dual signatures for bandwidth proofs
### Non-Repudiation
- Digital signatures provide non-repudiation
- Audit logs provide accountability
## Threat Model
### In-Scope Threats
1. **Passive Adversary**: Eavesdropping on network traffic
2. **Active Adversary**: Man-in-the-middle attacks
3. **Malicious Peer**: Byzantine behavior in P2P network
4. **Timing Attacks**: Side-channel information leakage
5. **Replay Attacks**: Reuse of bandwidth proofs
6. **Key Compromise**: Single key compromise
### Out-of-Scope Threats
1. **Physical Access**: Hardware tampering
2. **Side-Channel (Advanced)**: Power analysis, EM radiation
3. **Quantum Attacks**: Post-quantum security (future work)
4. **Social Engineering**: Non-cryptographic attacks
## Known Limitations
1. **RNG Dependency**: Relies on operating system RNG (rand crate)
2. **Timing Channels**: Perfect constant-time not guaranteed on all platforms
3. **Compiler Optimizations**: May introduce timing variations
4. **Post-Quantum**: Not resistant to quantum attacks
5. **Hardware**: No HSM integration in open-source version
## Dependencies
### Direct Cryptographic Dependencies
- `chacha20poly1305`: ChaCha20-Poly1305 AEAD (v0.10)
- `ed25519-dalek`: Ed25519 signatures (v2.1)
- `x25519-dalek`: X25519 key exchange (v2.0)
- `blake3`: BLAKE3 hashing (v1.5)
- `curve25519-dalek`: Curve25519 operations (v4.1)
- `hkdf`: HMAC-based KDF (v0.12)
- `sha2`: SHA-256/SHA-512 (v0.10)
- `argon2`: Argon2 password hashing (v0.5)
### Supporting Dependencies
- `rand`: Random number generation (v0.9)
- `zeroize`: Secure memory clearing (v1.7)
- `serde`: Serialization (v1.0)
- `bincode`: Binary serialization (v1.3)
All dependencies are from well-known, audited crates with active maintenance.
## Test Coverage
### Unit Tests
- **970 unit tests** covering all modules
- **100% pass rate**, zero warnings
- Edge cases, error conditions, regression tests
### Integration Tests
- **9 KAT vectors** from RFC specifications (8439, 8032, 5869, 7748)
- **10 cross-implementation** compatibility tests
- **12 MIRI memory safety** tests
- **13 constant-time** operation tests
### Fuzz Testing
- **8 fuzzing targets** using libFuzzer
- Cryptographic property testing
- Edge case discovery
### Memory Safety
- **MIRI verification** for undefined behavior
- No unsafe code in core modules
- Automated memory leak detection
### Constant-Time
- **Statistical analysis** of timing variations
- **Property-based testing** for timing independence
- **Documented guarantees** and limitations
## Code Quality
### Static Analysis
- **Clippy**: Rust linter (all warnings resolved)
- **Rustfmt**: Consistent code formatting
- **Cargo deny**: Dependency auditing
### Documentation
- **Doc comments** for all public APIs
- **86 doc tests** (all passing)
- **Examples** in documentation
### Code Review
- Peer review for all changes
- Security-focused review process
## Audit Recommendations
### Priority Areas
**High Priority:**
1. Constant-time comparison implementation (`ct.rs`)
2. Authentication tag verification (`encryption.rs`)
3. Signature verification (`signing.rs`)
4. Key derivation (`kdf.rs`)
5. Random number generation usage
**Medium Priority:**
6. Shamir secret sharing implementation (`shamir.rs`)
7. Merkle tree proof verification (`merkle.rs`)
8. VRF implementation (`vrf.rs`)
9. Pedersen commitment operations (`pedersen.rs`)
10. Threshold signature aggregation (`threshold.rs`)
**Low Priority:**
11. Serialization/deserialization
12. Utility functions
13. Logging and metrics
### Test Procedures
1. **Code Review**: Manual inspection of critical paths
2. **Fuzzing**: Extended fuzzing campaigns (48+ hours per target)
3. **Differential Testing**: Compare with reference implementations
4. **Side-Channel Analysis**: Timing measurements under various conditions
5. **Formal Verification**: Where applicable (constant-time properties)
### Tools and Methodologies
- **MIRI**: Memory safety verification
- **cargo-fuzz**: Coverage-guided fuzzing
- **dudect**: Constant-time verification
- **valgrind**: Memory leak detection
- **perf**: Performance profiling
## Compliance
### Standards Adherence
- **RFC 8439**: ChaCha20-Poly1305 AEAD
- **RFC 8032**: Ed25519 signatures
- **RFC 7748**: X25519 key exchange
- **RFC 5869**: HKDF key derivation
- **NIST SP 800-90B**: Entropy source validation
- **FIPS 140-3**: Compliance reporting (where applicable)
### Best Practices
- **OWASP Cryptographic Storage Cheat Sheet**
- **NIST Cryptographic Standards**
- **Mozilla Cryptographic Guidelines**
## Contact Information
For security issues and vulnerability reports:
- Email: [security contact]
- GPG Key: [if applicable]
- Bug Bounty: [if applicable]
## Revision History
- v0.1.0 (2026-01-18): Initial security audit documentation