Integrity Guarantee - Authenticated Encryption Architecture

ANKASecure© ensures 100% cryptographic integrity verification for all encrypted data through mandatory AEAD (Authenticated Encryption with Associated Data) for every encryption the platform performs.

Executive Summary

ANKASecure© implements a zero-trust integrity model where every encryption operation produces an authentication tag that is cryptographically bound to the ciphertext. Decryption always validates this tag before returning plaintext data.

Key Guarantees:

• 100% of symmetric algorithms use AEAD modes (GCM, CCM, Poly1305)
• 100% of asymmetric algorithms use authenticated padding (OAEP) or hybrid AEAD
• 100% of Post-Quantum KEMs use AES-256-GCM for content encryption
• No code paths exist that return decrypted data without integrity verification

Authenticated Encryption Modes

GCM (Galois/Counter Mode)

Used by: AES, Camellia, SEED, SM4, ARIA

GCM provides simultaneous confidentiality and authenticity using a 128-bit authentication tag. The tag is computed over both the ciphertext and any associated data (AAD), ensuring that any modification to either component is detected.

Technical Parameters:

Security Properties:

• Provides IND-CCA2 (Indistinguishability under Adaptive Chosen Ciphertext Attack)
• Detects bit-flip attacks with probability 1 - 2^(-128)
• Prevents ciphertext reordering and truncation attacks
• AAD binding prevents context manipulation

CCM (Counter with CBC-MAC)

Used by: AES, SM4, ARIA

CCM combines CTR mode encryption with CBC-MAC authentication, providing both confidentiality and authenticity in a single pass (with preprocessing).

Technical Parameters:

Security Properties:

• Provably secure under standard assumptions
• Suitable for constrained environments
• Resistant to timing attacks with proper implementation

Poly1305

Used by: ChaCha20-Poly1305

Poly1305 is a cryptographic message authentication code (MAC) designed for high-speed software implementations.

Technical Parameters:

Security Properties:

• Information-theoretic security (given unique key per message)
• Constant-time implementation prevents timing attacks
• IETF standard for TLS 1.3

Asymmetric Algorithm Integrity

RSA-OAEP (Optimal Asymmetric Encryption Padding)

All RSA encryption in ANKASecure© uses OAEP with SHA-512, which provides:

• Plaintext-awareness: Attacker cannot create valid ciphertexts without knowing plaintext
• Padding oracle immunity: Invalid padding is indistinguishable from decryption failure
• IND-CCA2 security: Proven secure against adaptive chosen-ciphertext attacks

Configuration:

ECDH-ES Key Agreement

Elliptic Curve Diffie-Hellman Ephemeral-Static key agreement uses:

• A256KW (AES Key Wrap): Includes 64-bit Integrity Check Value (ICV)
• Content Encryption: AES-256-GCM with 128-bit authentication tag
• Key Derivation: NIST Concat KDF with algorithm-specific context

Post-Quantum KEM Hybrid Encryption

All PQC KEMs (ML-KEM, HQC, FrodoKEM, BIKE, SABER, NTRU, etc.) use hybrid encryption:

1. Key Encapsulation: KEM produces shared secret
2. Key Derivation: HKDF-SHA256 derives content encryption key
3. Content Encryption: Always AES-256-GCM with 128-bit tag

This ensures quantum-resistant key exchange combined with proven symmetric AEAD.

Authentication Tag Validation Architecture

Validation Flow

flowchart TD
    A["/"<b>DECRYPTION REQUEST</b>"/"]

    B["<b>1. Parse JWE/Ciphertext Structure</b><br/>• Extract IV, ciphertext, authentication tag<br/>• Validate header parameters"]

    C["<b>2. Initialize AEAD Cipher</b><br/>• Load decryption key from keystore<br/>• Configure GCM/CCM/Poly1305 parameters<br/>• Set tag length to 128 bits"]

    D["<b>3. Process Ciphertext + Tag</b><br/>• Concatenate ciphertext with authentication tag<br/>• Execute cipher.doFinal()"]

    E{"<b>Tag Valid?</b>"}

    F["<b>✓ SUCCESS</b><br/>Return plaintext"]

    G["<b>✗ FAILURE</b><br/>AEADBadTagException<br/>→ HTTP 422<br/>'Integrity failed'"]

    A --> B
    B --> C
    C --> D
    D --> E
    E -->|Yes| F
    E -->|No| G

    style A fill:#e1f5fe,stroke:#01579b,stroke-width:2px
    style B fill:#fff3e0,stroke:#e65100,stroke-width:1px
    style C fill:#fff3e0,stroke:#e65100,stroke-width:1px
    style D fill:#fff3e0,stroke:#e65100,stroke-width:1px
    style E fill:#fce4ec,stroke:#880e4f,stroke-width:2px
    style F fill:#e8f5e9,stroke:#1b5e20,stroke-width:2px
    style G fill:#ffebee,stroke:#b71c1c,stroke-width:2px

Constant-Time Comparison

All MAC/tag comparisons use constant-time algorithms to prevent timing attacks:

• Java's MessageDigest.isEqual() for byte array comparison
• No early-exit on mismatch
• Fixed execution time regardless of data content

Algorithm Coverage Matrix

Symmetric Algorithms (100% AEAD)

Asymmetric/Hybrid Algorithms (100% Authenticated)

Signature Algorithms (Integrity by Design)

Security Guarantees

What ANKASecure© Guarantees

1. Tamper Detection: Any modification to ciphertext is detected with probability 1 - 2^(-128)
2. Authenticity: Ciphertext provably originated from a key holder
3. No Silent Failures: Invalid integrity always raises an exception
4. Audit Trail: All integrity failures are logged with correlation IDs

Attack Vectors Mitigated

Standards Compliance

ANKASecure© integrity mechanisms comply with:

Operational Considerations

Performance Impact

AEAD modes add minimal overhead compared to unauthenticated encryption:

Error Handling

When integrity verification fails:

1. Exception: AEADBadTagException (Java) or equivalent
2. HTTP Response: 422 Unprocessable Entity
3. Message: "Ciphertext integrity verification failed"
4. Logging: WARN level with transaction ID (no sensitive data)
5. No Partial Data: Entire operation fails atomically

Verification and Audit

Runtime Verification

Integrity is verified at multiple levels:

1. Algorithm Catalog: Only AEAD algorithms are available
2. Cipher Initialization: Tag length enforced at cipher setup
3. Decryption: doFinal() validates tag before returning data
4. JWE Processing: Tag extracted and verified per RFC 7516

Audit Capabilities

• All crypto operations logged with correlation IDs
• Integrity failures generate security alerts
• Usage metrics track authentication success/failure rates

Related Documentation

• Algorithm Catalog - Complete algorithm reference
• Performance Benchmarks - Algorithm performance data
• Key Management^* - Key lifecycle and storage
• Encryption & Digital Signatures^* - Implementation details