Security Model

DEVELOPMENT STATUS WARNING

This security model describes the INTENDED security properties of Cypheron Core v0.1.0.

CRITICAL: This is a Rust wrapper around official NIST reference implementations - not custom cryptography. The core algorithms are NIST-certified, but the Rust integration layer is experimental and has NOT been:

• Independently audited for FFI safety
• Formally verified for memory management
• Validated in production environments

Integration layer uses C vendor code with Rust FFI bindings requiring security evaluation.

Cypheron Core’s security model describes intended cryptographic foundations and defensive programming practices.

Threat Model

Adversarial Capabilities

We protect against adversaries with the following capabilities:

1. Classical Computers: Unlimited classical computational power
2. Quantum Computers: Large-scale fault-tolerant quantum computers
3. Side-Channel Attacks: Timing, power, and electromagnetic analysis
4. Memory Attacks: Cold boot attacks, memory dumps, swap file analysis

Security Goals

• Confidentiality: Encrypted data remains secret
• Authenticity: Signatures prove message origin
• Integrity: Tampering is detectable
• Forward Secrecy: Past communications remain secure if keys are compromised

Cryptographic Security

Post-Quantum Resistance

All algorithms are designed to resist quantum computer attacks:

• ML-KEM: Based on Module Learning With Errors (M-LWE)
• ML-DSA: Based on Module Short Integer Solution (M-SIS)
• Falcon: Based on NTRU lattices and Gaussian sampling
• SPHINCS+: Based on hash functions and one-time signatures

Security Levels

Implementation Security

Constant-Time Operations

All cryptographic operations execute in constant time:

#![allow(unused)]
fn main() {
// Example: Constant-time secret key usage
let (pk, sk) = MlKem768::keypair()?;
let (ct, ss) = MlKem768::encapsulate(&pk)?;

// Decapsulation time is independent of:
// - Secret key content
// - Ciphertext validity  
// - Previous operations
let result = MlKem768::decapsulate(&ct, &sk)?;
}

Memory Protection

Sensitive data is automatically protected:

#![allow(unused)]
fn main() {
use secrecy::ExposeSecret;

{
    let (pk, sk) = MlKem768::keypair()?;
    
    // Secret key is in protected memory
    let secret_data = sk.0.expose_secret();
    
    // Use secret_data...
    
} // Secret key memory is zeroized automatically
}

Randomness Requirements

Cryptographic operations require high-quality randomness:

• Entropy Sources: Hardware RNG, OS entropy pools
• Seeding: Proper CSPRNG initialization
• Reseeding: Regular entropy pool updates

#![allow(unused)]
fn main() {
// Entropy failure is handled gracefully
match MlKem768::keypair() {
    Ok((pk, sk)) => { /* success */ },
    Err(MlKemError::KeyGenerationEntropyFailure) => {
        // Handle insufficient entropy
        std::thread::sleep(std::time::Duration::from_millis(100));
        // Retry...
    },
    Err(e) => return Err(e),
}
}

Side-Channel Protection

Timing Attacks

All operations use constant-time algorithms:

• No secret-dependent branches: Control flow is independent of secrets
• No secret-dependent memory access: Memory patterns are predictable
• No secret-dependent loop bounds: Iteration counts are fixed

Power Analysis

Operations are designed to minimize power analysis vulnerabilities:

• Uniform operations: Similar power consumption patterns
• Masked arithmetic: Secret values are never used directly
• Randomized execution: Some operations include deliberate randomness

Fault Injection

Critical operations include integrity checks:

#![allow(unused)]
fn main() {
// Example: Built-in integrity verification
let (pk, sk) = MlKem768::keypair()?;
let (ct, ss1) = MlKem768::encapsulate(&pk)?;

// Decapsulation includes implicit ciphertext validation
match MlKem768::decapsulate(&ct, &sk) {
    Ok(ss2) => {
        // ss1 and ss2 are identical if no faults occurred
        assert_eq!(ss1.expose_secret(), ss2.expose_secret());
    },
    Err(MlKemError::DecapsulationInvalidCiphertext) => {
        // Ciphertext was corrupted or maliciously modified
    },
}
}

Key Management

Key Lifecycle

1. Generation: High-entropy key creation
2. Storage: Encrypted at rest when possible
3. Usage: Minimal exposure time
4. Destruction: Cryptographic erasure

#![allow(unused)]
fn main() {
// Proper key lifecycle management
fn secure_key_usage() -> Result<(), Box<dyn std::error::Error>> {
    // 1. Generation
    let (pk, sk) = MlKem768::keypair()?;
    
    // 2. Usage (minimize exposure time)
    let (ct, ss) = MlKem768::encapsulate(&pk)?;
    
    // 3. Destruction is automatic when variables go out of scope
    Ok(())
} // Keys are zeroized here
}

Key Rotation

Regular key rotation is recommended:

#![allow(unused)]
fn main() {
use std::time::{Duration, Instant};

struct KeyManager {
    current_keys: (MlKemPublicKey, MlKemSecretKey),
    created_at: Instant,
    rotation_interval: Duration,
}

impl KeyManager {
    fn should_rotate(&self) -> bool {
        self.created_at.elapsed() > self.rotation_interval
    }
    
    fn rotate(&mut self) -> Result<(), MlKemError> {
        if self.should_rotate() {
            self.current_keys = MlKem768::keypair()?;
            self.created_at = Instant::now();
        }
        Ok(())
    }
}
}

Compliance and Standards

NIST Standardization

All algorithms implement NIST-standardized specifications:

• FIPS 203: ML-KEM standard
• FIPS 204: ML-DSA standard
• FIPS 205: SPHINCS+ standard

Security Validations

• Known Answer Tests (KAT): Validation against NIST test vectors
• Monte Carlo Testing: Statistical randomness validation
• Side-Channel Testing: Timing and power analysis resistance

Limitations and Assumptions

Trust Assumptions

• Implementation Correctness: No bugs in cryptographic implementations
• Hardware Security: CPU and memory provide basic security guarantees
• Random Number Generation: OS provides cryptographically secure randomness

Known Limitations

• No Perfect Forward Secrecy: KEM schemes don’t provide PFS by default
• Post-Quantum Assumptions: Security relies on unproven mathematical assumptions
• Implementation Attacks: Hardware vulnerabilities could compromise security

Best Practices

Application Security

#![allow(unused)]
fn main() {
// ✅ Good: Validate all inputs
if ciphertext.len() != EXPECTED_CIPHERTEXT_SIZE {
    return Err("Invalid ciphertext size");
}

// ✅ Good: Handle errors appropriately  
match MlKem768::decapsulate(&ct, &sk) {
    Ok(ss) => use_shared_secret(ss),
    Err(e) => log_security_event(e),
}

// ❌ Bad: Ignoring security-critical errors
let ss = MlKem768::decapsulate(&ct, &sk).unwrap(); // Don't do this!
}

Operational Security

1. Monitor Entropy: Check system entropy levels
2. Log Security Events: Record cryptographic failures
3. Update Regularly: Keep libraries up to date
4. Test Thoroughly: Validate all error paths

See Also

• Side-Channel Protection - Detailed protection mechanisms
• Memory Safety - Memory security guarantees
• Compliance - Standards compliance