Namespace: WvdS.System.Security.Cryptography.KeyDerivation

Statička klasa za derivaciju ključeva (Key Derivation Functions) s Post-Quantum podrškom. Podržava HKDF, PBKDF2 i Argon2id.

Podržani KDF algoritmi:

Derivira ključeve iz dijeljenog tajnog ključa (HKDF-Extract-then-Expand).

// ML-KEM dijeljeni tajni ključ iz Key Exchange
byte[] sharedSecret = session.SharedSecret;
 
// Standardna derivacija (SHA-256)
byte[] aesKey = KeyDerivationExtensions.DeriveKey(
    sharedSecret,
    outputLength: 32);  // 256 bita
 
// Sa salt i kontekst informacijom
byte[] salt = RandomNumberGenerator.GetBytes(32);
byte[] info = Encoding.UTF8.GetBytes("MyApp-Session-Key");
 
byte[] sessionKey = KeyDerivationExtensions.DeriveKey(
    sharedSecret,
    outputLength: 32,
    salt: salt,
    info: info,
    hashAlgorithm: HashAlgorithmName.SHA384);  // Opcionalno

Ekstrahira PRK (Pseudorandom Key) iz ulaznog ključnog materijala.

byte[] inputKeyMaterial = GetSharedSecret();
byte[] salt = RandomNumberGenerator.GetBytes(32);
 
byte[] prk = KeyDerivationExtensions.HkdfExtract(
    inputKeyMaterial,
    salt: salt,
    hashAlgorithm: HashAlgorithmName.SHA256);
 
// PRK ima istu duljinu kao hash izlaz (32 bajta za SHA-256)

Proširuje PRK na izlazni ključni materijal.

byte[] prk = GetPrk();
 
// Ključ za šifriranje
byte[] encKey = KeyDerivationExtensions.HkdfExpand(
    prk,
    outputLength: 32,
    info: Encoding.UTF8.GetBytes("encryption"));
 
// MAC ključ
byte[] macKey = KeyDerivationExtensions.HkdfExpand(
    prk,
    outputLength: 32,
    info: Encoding.UTF8.GetBytes("mac"));

Kombinira klasične (ECDH/DH) i PQ (ML-KEM) dijeljene tajne ključeve.

byte[] ecdhSecret = GetEcdhSharedSecret();
byte[] mlKemSecret = GetMlKemSharedSecret();
 
// Hibridni način: Oba tajni ključa se kombiniraju
byte[] hybridKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    outputLength: 32,
    mode: CryptoMode.Hybrid);
 
// Samo klasični
byte[] classicKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: null,
    outputLength: 32,
    mode: CryptoMode.Classic);
 
// Samo Post-Quantum
byte[] pqKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: null,
    pqSecret: mlKemSecret,
    outputLength: 32,
    mode: CryptoMode.PostQuantum);
 
// Prilagođeni info
byte[] customKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    outputLength: 64,
    mode: CryptoMode.Hybrid,
    info: Encoding.UTF8.GetBytes("MyProtocol-v1"));

Kombinacija ključeva:

Hibridni način:
  IKM = classicSecret || pqSecret
  Key = HKDF-SHA256(IKM, info="WvdS-Hybrid-Key")

Derivira više ključeva za različite namjene.

using HybridKeyMaterial keyMaterial = KeyDerivationExtensions.DeriveHybridKeyMaterial(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    mode: CryptoMode.Hybrid);
 
// Uporaba
byte[] encKey = keyMaterial.EncryptionKey;  // 32 bajta
byte[] macKey = keyMaterial.MacKey;         // 32 bajta
byte[] iv = keyMaterial.Iv;                 // 16 bajtova
byte[] authKey = keyMaterial.AuthKey;       // 32 bajta
 
// IDisposable: Ključevi se sigurno brišu

string password = "SecurePassword123!";
byte[] salt = RandomNumberGenerator.GetBytes(32);
 
// Standardni PBKDF2
byte[] key = KeyDerivationExtensions.Pbkdf2(
    password,
    salt,
    iterations: 100000,
    outputLength: 32);
 
// S PQ-entropijom (dodatna zaštita)
byte[] pqEntropy = GetPqEntropy();
 
byte[] enhancedKey = KeyDerivationExtensions.Pbkdf2(
    password,
    salt,
    iterations: 100000,
    outputLength: 32,
    pqEntropy: pqEntropy,  // Kombinira se sa salt
    hashAlgorithm: HashAlgorithmName.SHA512);

PBKDF2 s PQ-pojačanim salt (javni ključ uključen je u izračun salt).

string password = "UserPassword";
byte[] baseSalt = RandomNumberGenerator.GetBytes(16);
byte[] mlKemPublicKey = GetRecipientPublicKey();
 
// Salt = SHA256(baseSalt || pqPublicKey)
byte[] key = KeyDerivationExtensions.Pbkdf2WithPqSalt(
    password,
    baseSalt,
    mlKemPublicKey,
    iterations: 100000,
    outputLength: 32);

Argon2id putem OpenSSL 3.6 - otporan na GPU/ASIC napade.

byte[] password = Encoding.UTF8.GetBytes("SecurePassword");
byte[] salt = RandomNumberGenerator.GetBytes(16);  // Najmanje 16 bajtova
 
byte[] key = KeyDerivationExtensions.Argon2id(
    password,
    salt,
    outputLength: 32,     // Duljina ključa
    iterations: 3,        // Vremenski trošak (t)
    memoryKiB: 65536,     // Memorija: 64 MB
    parallelism: 4);      // Niti (p)

string password = "UserPassword123";
byte[] salt = RandomNumberGenerator.GetBytes(16);
 
byte[] key = KeyDerivationExtensions.Argon2id(
    password,
    salt,
    outputLength: 32,
    iterations: 3,
    memoryKiB: 65536,
    parallelism: 4);

Preporučeni parametri:

byte[] preMasterSecret = GetPreMasterSecret();
byte[] clientRandom = GetClientRandom();
byte[] serverRandom = GetServerRandom();
 
using TlsKeyMaterial keys = KeyDerivationExtensions.DeriveTlsKeys(
    preMasterSecret,
    clientRandom,
    serverRandom,
    mode: CryptoMode.Hybrid);
 
// Uporaba
var clientKey = keys.ClientWriteKey;   // 32 bajta
var serverKey = keys.ServerWriteKey;   // 32 bajta
var clientIv = keys.ClientWriteIv;     // 12 bajtova
var serverIv = keys.ServerWriteIv;     // 12 bajtova

TLS 1.3 kompatibilan raspored ključeva.

byte[]? pskSecret = null;  // Pre-Shared Key (opcionalno)
byte[] ecdhSecret = GetEcdhSecret();
byte[] pqSecret = GetMlKemSecret();
byte[] clientHello = GetClientHelloBytes();
byte[] serverHello = GetServerHelloBytes();
 
using Tls13KeySchedule schedule = KeyDerivationExtensions.DeriveTls13Keys(
    pskSecret,
    ecdhSecret,
    pqSecret,
    clientHello,
    serverHello,
    mode: CryptoMode.Hybrid);
 
// Handshake Traffic Secrets
var clientHsSecret = schedule.ClientHandshakeTrafficSecret;
var serverHsSecret = schedule.ServerHandshakeTrafficSecret;
 
// Application Traffic Secrets
var clientAppSecret = schedule.ClientApplicationTrafficSecret;
var serverAppSecret = schedule.ServerApplicationTrafficSecret;
 
// Resumption Secret
var resumptionSecret = schedule.ResumptionMasterSecret;

Kontejner za derivirane ključeve sa sigurnim čišćenjem memorije.

using HybridKeyMaterial keys = DeriveKeys();
 
// Ključevi se sigurno brišu pri Dispose()
// (CryptographicOperations.ZeroMemory)

TLS 1.2 stil ključni materijal.

TLS 1.3 raspored ključeva.

using WvdS.System.Security.Cryptography;
using WvdS.System.Security.Cryptography.KeyDerivation;
using WvdS.System.Security.Cryptography.KeyExchange;
 
// 1. Izvršiti Key Exchange
using var session = new KeyExchangeService();
await session.InitiateKeyExchangeAsync(recipientPublicKey, CryptoMode.Hybrid);
 
// 2. Derivirati hibridni ključni materijal
using HybridKeyMaterial keys = KeyDerivationExtensions.DeriveHybridKeyMaterial(
    classicSecret: session.ClassicSharedSecret,
    pqSecret: session.PqSharedSecret,
    mode: CryptoMode.Hybrid);
 
// 3. Koristiti ključeve
using var aes = Aes.Create();
aes.Key = keys.EncryptionKey;
 
using var hmac = new HMACSHA256(keys.MacKey);
 
// 4. Izvršiti šifriranje
// ...
 
// 5. Ključevi se automatski sigurno brišu

• KeyDerivation prostor imena
• HybridKeyMaterial
• TlsKeyMaterial
• Tls13KeySchedule
• KeyExchange prostor imena
• Encryption prostor imena
• ML-KEM algoritam

Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional