~~NOTOC~~
{{wvds:title>Glossary}}

===== Glossary: Post-Quantum Cryptography =====

==== Cryptographic Methods ====

=== ML-KEM (Module-Lattice Key Encapsulation) ===

| Standard | FIPS 203 |
| Purpose | Key exchange |
| Security | Post-Quantum secure |

ML-KEM replaces classical methods like RSA or ECDH for key exchange. It's based on the "Learning with Errors" (LWE) problem, which is hard to solve even for quantum computers.

**Operations:**
  * **KeyGen** - Generate key pair (Public + Private)
  * **Encaps** - Create Shared Secret + Ciphertext from Public Key
  * **Decaps** - Extract Shared Secret from Ciphertext + Private Key

=== ML-DSA (Module-Lattice Digital Signature) ===

| Standard | FIPS 204 |
| Purpose | Digital signatures |
| Security | Post-Quantum secure |

ML-DSA replaces RSA/ECDSA for digital signatures. Also lattice-based.

**Operations:**
  * **Sign** - Sign message with Private Key
  * **Verify** - Verify signature with Public Key

=== AES-256-GCM ===

| Standard | NIST SP 800-38D |
| Purpose | Authenticated encryption |
| Key Length | 256 bits |

AES-GCM provides simultaneous encryption AND integrity protection. The GCM mode creates an Authentication Tag that detects tampering.

**Components:**
  * **Key** - 256-bit key
  * **Nonce** - 12-byte initialization vector (NEVER reuse!)
  * **AAD** - Additional Authenticated Data (unencrypted but authenticated)
  * **Tag** - 16-byte Authentication Tag

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==== Security Concepts ====

=== Nonce (Number Used Once) ===

| Size | 12 bytes (96 bits) |
| Critical | NEVER reuse! |

A nonce is a number that may only be used once per key. With AES-GCM, nonce reuse leads to complete compromise:

<WRAP center round alert 80%>
**Nonce Reuse = Catastrophe**

If the same nonce is used twice with the same key, an attacker can reconstruct both plaintexts!
</WRAP>

The WvdS Crypto Service automatically protects against nonce reuse through tracking.

=== AAD (Additional Authenticated Data) ===

Data that is NOT encrypted but protected by the Authentication Tag. Typical use:

  * Metadata (timestamp, sender ID)
  * Routing information
  * Version numbers

=== Zeroize ===

Security-critical data (keys, plaintexts) is actively overwritten with zeros after use. This prevents memory dumps from containing sensitive data.

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==== Standards & Compliance ====

=== FIPS (Federal Information Processing Standards) ===

US standards for cryptographic modules:

| FIPS 140-3 | Security requirements for crypto modules |
| FIPS 203 | ML-KEM (Kyber) |
| FIPS 204 | ML-DSA (Dilithium) |

=== BSI TR-03116-4 ===

Technical guideline from BSI for cryptographic requirements in eHealth systems. Defines allowed algorithms and key lengths.

=== NIS2 ===

EU directive on network and information security. Article 21 requires "state of the art" cryptography for critical infrastructure.

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==== Hardware ====

=== HSM (Hardware Security Module) ===

Dedicated hardware for cryptographic operations. Keys never leave the HSM in plaintext.

=== TPM (Trusted Platform Module) ===

Chip on the motherboard for:
  * Secure Boot verification
  * Key storage
  * Platform attestation

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