Classical Cryptography Threat Model

Version: 1.0
Last Updated: 2025-01-02
Security Classification: PUBLIC
Author: MetaMUI Security Team

Executive Summary

This document defines the comprehensive threat model for classical cryptographic implementations in the MetaMUI ecosystem. It covers symmetric encryption, hash functions, digital signatures, and key derivation functions, analyzing both current and emerging threats.

Threat Landscape

Current Threat Environment

Classical cryptography faces threats from:

• Computational Advances: Increasing computational power
• Cryptanalytic Progress: New attack techniques
• Implementation Vulnerabilities: Side-channel and fault attacks
• Quantum Computing: Future threat requiring migration planning

Algorithm Categories and Threats

Hash Functions

SHA-2 Family (SHA-256/384/512)

Primary Threats:

• Length extension attacks (mitigated by HMAC construction)
• Collision attacks (theoretical, not practical)
• Preimage attacks (computationally infeasible)

Security Levels:

sha_security = {
    'SHA-256': {'collision': 128, 'preimage': 256, 'quantum': 128},
    'SHA-384': {'collision': 192, 'preimage': 384, 'quantum': 192},
    'SHA-512': {'collision': 256, 'preimage': 512, 'quantum': 256}
}

SHA-3 Family (Keccak Sponge)

Primary Threats:

• State recovery attacks (prevented by capacity)
• Cube attacks (theoretical on reduced rounds)
• Side-channel leakage in software implementations

Security Analysis:

def keccak_security(capacity_bits: int) -> dict:
    """Calculate Keccak sponge security levels"""
    return {
        'collision_resistance': capacity_bits // 2,
        'preimage_resistance': min(capacity_bits // 2, 256),
        'second_preimage': capacity_bits // 2,
        'indifferentiability': capacity_bits // 2
    }

BLAKE Family (BLAKE2b/2s/3)

Primary Threats:

• Differential cryptanalysis (no practical attacks)
• Rotational cryptanalysis (mitigated by constants)
• Implementation timing attacks

Symmetric Encryption

AES-256

Primary Threats:

• Related-key attacks (theoretical on full AES-256)
• Cache-timing attacks (implementation dependent)
• Fault injection attacks (DFA on AES)
• Side-channel attacks (power analysis, EM)

Attack Complexity:

aes_attack_complexity = {
    'brute_force': 2**256,
    'biclique': 2**254.4,  # Marginal improvement
    'quantum_grover': 2**128,
    'related_key': 2**99.5,  # 256-bit only, not practical
    'cache_timing': 'implementation_dependent'
}

ChaCha20

Primary Threats:

• Differential cryptanalysis (no attacks on full 20 rounds)
• Nonce reuse (catastrophic for security)
• Implementation errors in quarter-round function

Security Guarantees:

chacha20_security = {
    'key_recovery': 2**256,
    'distinguisher': 2**256,  # No known distinguishers
    'nonce_reuse': 'complete_break',
    'rounds_broken': 7,  # Out of 20
    'quantum_resistance': 2**128
}

Digital Signatures

Ed25519

Primary Threats:

• Shor’s algorithm (complete break with quantum computers)
• Fault attacks on signature generation
• Implementation bugs (e.g., nonce generation)
• Side-channel attacks on scalar multiplication

Threat Timeline:

ed25519_quantum_timeline = {
    2025: 'safe',
    2030: 'monitor',
    2035: 'high_risk',
    2040: 'likely_broken'
}

Implementation Vulnerabilities

Side-Channel Attacks

class SideChannelVulnerabilities:
    """Classical crypto side-channel attack vectors"""
    
    timing_attacks = {
        'vulnerable_operations': [
            'table_lookups',
            'conditional_branches',
            'cache_access_patterns',
            'variable_time_arithmetic'
        ],
        'mitigation': 'constant_time_implementation'
    }
    
    power_analysis = {
        'simple_power_analysis': 'key_bit_recovery',
        'differential_power_analysis': 'statistical_key_recovery',
        'correlation_power_analysis': 'template_attacks',
        'mitigation': 'masking_and_shuffling'
    }
    
    fault_injection = {
        'voltage_glitching': 'skip_instructions',
        'clock_glitching': 'corrupt_computations',
        'laser_injection': 'flip_bits',
        'software_faults': 'rowhammer_style',
        'mitigation': 'redundancy_and_checks'
    }

Memory Vulnerabilities

class MemoryAttacks:
    """Memory-based attack vectors"""
    
    cold_boot = {
        'threat': 'key_recovery_from_ram',
        'persistence': '5-60_seconds',
        'mitigation': 'memory_encryption'
    }
    
    swap_file = {
        'threat': 'key_recovery_from_disk',
        'persistence': 'permanent',
        'mitigation': 'disable_swap_or_encrypt'
    }
    
    memory_disclosure = {
        'heartbleed_style': 'buffer_overread',
        'use_after_free': 'stale_pointers',
        'uninitialized_memory': 'information_leak',
        'mitigation': 'secure_coding_practices'
    }

Cryptanalytic Advances

Current Research Threats

class CryptanalyticThreats:
    """Emerging cryptanalytic techniques"""
    
    machine_learning = {
        'threat_level': 'research',
        'target': 'implementation_patterns',
        'success_rate': 'limited',
        'timeline': '5-10_years'
    }
    
    quantum_inspired = {
        'threat_level': 'theoretical',
        'algorithms': ['quantum_annealing', 'tensor_networks'],
        'impact': 'marginal_speedup',
        'timeline': 'current'
    }
    
    algebraic_attacks = {
        'threat_level': 'algorithm_specific',
        'vulnerable': 'lightweight_ciphers',
        'mitigation': 'proper_design'
    }

Protocol-Level Threats

Key Management

class KeyManagementThreats:
    """Threats to key lifecycle"""
    
    generation = {
        'weak_entropy': 'predictable_keys',
        'flawed_rng': 'biased_output',
        'mitigation': 'hardware_rng_with_testing'
    }
    
    storage = {
        'plaintext_keys': 'direct_compromise',
        'weak_encryption': 'offline_attacks',
        'mitigation': 'hsm_or_key_wrapping'
    }
    
    distribution = {
        'mitm_attacks': 'key_substitution',
        'weak_authentication': 'impersonation',
        'mitigation': 'authenticated_key_exchange'
    }
    
    rotation = {
        'stale_keys': 'increased_exposure',
        'poor_timing': 'service_disruption',
        'mitigation': 'automated_rotation'
    }

Downgrade Attacks

def assess_downgrade_risk(protocol: dict) -> str:
    """Evaluate protocol downgrade attack risk"""
    
    if not protocol.get('version_binding'):
        return 'critical'
    
    if protocol.get('legacy_support'):
        return 'high'
    
    if not protocol.get('authenticated_negotiation'):
        return 'medium'
    
    return 'low'

Quantum Computing Impact

Grover’s Algorithm Impact

def grover_impact(algorithm: str, key_bits: int) -> dict:
    """Calculate Grover's algorithm impact"""
    
    classical_security = key_bits
    quantum_security = key_bits // 2
    
    return {
        'algorithm': algorithm,
        'classical_bits': classical_security,
        'quantum_bits': quantum_security,
        'requires_doubling': quantum_security < 128,
        'migration_priority': 'medium'
    }

Shor’s Algorithm Impact

def shor_impact(algorithm: str) -> dict:
    """Assess Shor's algorithm impact"""
    
    vulnerable = ['RSA', 'ECDSA', 'DSA', 'DH', 'ECDH']
    safe = ['AES', 'SHA-256', 'ChaCha20']
    
    if algorithm in vulnerable:
        return {
            'status': 'completely_broken',
            'timeline': '5-15_years',
            'action': 'migrate_to_pqc_immediately'
        }
    elif algorithm in safe:
        return {
            'status': 'requires_larger_keys',
            'timeline': 'long_term',
            'action': 'double_key_sizes'
        }

Risk Assessment Matrix

Algorithm Risk Levels

Algorithm	Current Risk	5-Year Risk	10-Year Risk	Quantum Risk
AES-256	Very Low	Very Low	Low	Medium*
ChaCha20	Very Low	Very Low	Low	Medium*
SHA-256	Very Low	Very Low	Low	Low**
SHA3-256	Very Low	Very Low	Very Low	Low**
BLAKE3	Very Low	Very Low	Very Low	Low**
Ed25519	Very Low	Low	High	Critical
HMAC-SHA256	Very Low	Very Low	Low	Low**
Argon2id	Very Low	Very Low	Very Low	Low

*Requires 2x key size for quantum resistance
**Grover provides only quadratic speedup

Mitigation Strategies

Defense in Depth

class DefenseStrategies:
    """Layered defense for classical crypto"""
    
    def build_defense_layers(self) -> list:
        return [
            {
                'layer': 1,
                'name': 'Algorithm Selection',
                'actions': ['use_recommended_algorithms', 'avoid_deprecated']
            },
            {
                'layer': 2,
                'name': 'Key Management',
                'actions': ['secure_generation', 'protected_storage', 'regular_rotation']
            },
            {
                'layer': 3,
                'name': 'Implementation Security',
                'actions': ['constant_time_code', 'side_channel_protection']
            },
            {
                'layer': 4,
                'name': 'Protocol Security',
                'actions': ['authenticated_encryption', 'forward_secrecy']
            },
            {
                'layer': 5,
                'name': 'Monitoring',
                'actions': ['anomaly_detection', 'security_logging']
            }
        ]

Migration Planning

class MigrationStrategy:
    """Plan for quantum-resistant migration"""
    
    priority_levels = {
        'immediate': ['long_term_signatures', 'root_certificates'],
        'high': ['key_exchange', 'vpn_tunnels'],
        'medium': ['tls_certificates', 'email_encryption'],
        'low': ['session_keys', 'short_lived_tokens']
    }
    
    hybrid_approach = {
        'phase1': 'add_pqc_alongside_classical',
        'phase2': 'prefer_pqc_when_available',
        'phase3': 'deprecate_vulnerable_classical',
        'phase4': 'pqc_only_deployment'
    }

Compliance Considerations

Standards Compliance

Standard	Requirement	Timeline	Impact
NIST SP 800-131A	Transition from weak crypto	Current	High
FIPS 140-3	Validated implementations	Current	High
PCI DSS	Strong cryptography	Current	Medium
GDPR	Appropriate security	Current	Medium
CCPA	Reasonable security	Current	Medium

Monitoring and Detection

class ThreatMonitoring:
    """Monitor for cryptographic threats"""
    
    def detect_attacks(self) -> dict:
        indicators = {
            'timing_anomalies': self.check_response_times(),
            'failed_verifications': self.count_auth_failures(),
            'unusual_patterns': self.analyze_usage_patterns(),
            'side_channel_indicators': self.monitor_power_em()
        }
        return indicators
    
    def threat_intelligence(self) -> dict:
        return {
            'cve_monitoring': 'check_vulnerability_databases',
            'research_tracking': 'follow_cryptanalytic_advances',
            'standard_updates': 'monitor_nist_recommendations',
            'vendor_advisories': 'track_implementation_issues'
        }

Incident Response

class IncidentResponse:
    """Cryptographic incident response procedures"""
    
    severity_levels = {
        'critical': 'key_compromise_or_algorithm_break',
        'high': 'implementation_vulnerability',
        'medium': 'theoretical_weakness',
        'low': 'configuration_issue'
    }
    
    response_actions = {
        'immediate': ['isolate_affected_systems', 'revoke_compromised_keys'],
        'short_term': ['patch_vulnerabilities', 'rotate_keys'],
        'long_term': ['algorithm_migration', 'protocol_upgrade']
    }

Future Considerations

Emerging Threats

• Quantum computing advancement
• AI-assisted cryptanalysis
• Supply chain attacks on implementations
• New side-channel techniques

Technology Trends

• Homomorphic encryption adoption
• Secure multi-party computation
• Zero-knowledge proofs
• Threshold cryptography

References

1. NIST Cryptographic Standards
2. eSTREAM Portfolio
3. IACR ePrint Archive
4. ENISA Cryptographic Guidelines
5. BSI Technical Guidelines

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Related Documentation

• PQC Threat Model
• Hybrid System Threats
• Algorithm-Specific Threat Models
• Security Best Practices