/// <summary>
/// Computes a derived key.
/// </summary>
/// <param name="hmacAlgorithm">
/// </param>
/// <param name="salt">
/// The salt.
/// A unique salt means a unique derived key, even if the original key is identical.
/// </param>
/// <param name="iterations">The number of iterations to apply.</param>
/// <param name="derivedKeyLength">The desired length of the derived key.</param>
/// <returns>The derived key.</returns>
public static byte[] ComputeDerivedKey(KeyedHashAlgorithm hmacAlgorithm, byte[] salt, int iterations,
int derivedKeyLength)
{
NBitcoin.Crypto.Internal.Check.Range("derivedKeyLength", derivedKeyLength, 0, int.MaxValue);
using (Pbkdf2 kdf = new Pbkdf2(hmacAlgorithm, salt, iterations))
{
return(kdf.Read(derivedKeyLength));
}
}
/// <summary>
/// Computes a derived key.
/// </summary>
/// <param name="hmacAlgorithm">
/// The HMAC algorithm to use, for example <see cref="HMACSHA256"/>.
/// Make sure to set <see cref="KeyedHashAlgorithm.Key"/>.
/// </param>
/// <param name="salt">
/// The salt.
/// A unique salt means a unique derived key, even if the original key is identical.
/// </param>
/// <param name="iterations">The number of iterations to apply.</param>
/// <param name="derivedKeyLength">The desired length of the derived key.</param>
/// <returns>The derived key.</returns>
public static byte[] ComputeDerivedKey(KeyedHashAlgorithm hmacAlgorithm, byte[] salt, int iterations,
int derivedKeyLength)
{
Check.Range("derivedKeyLength", derivedKeyLength, 0, int.MaxValue);
using (Pbkdf2 kdf = new Pbkdf2(hmacAlgorithm, salt, iterations))
{
return kdf.Read(derivedKeyLength);
}
}
/// <summary>
/// Creates a derived key stream from which a derived key can be read.
/// </summary>
/// <param name="key">The key to derive from.</param>
/// <param name="salt">
/// The salt.
/// A unique salt means a unique scrypt stream, even if the original key is identical.
/// </param>
/// <param name="cost">
/// The cost parameter, typically a fairly large number such as 262144.
/// Memory usage and CPU time scale approximately linearly with this parameter.
/// </param>
/// <param name="blockSize">
/// The mixing block size, typically 8.
/// Memory usage and CPU time scale approximately linearly with this parameter.
/// </param>
/// <param name="parallel">
/// The level of parallelism, typically 1.
/// CPU time scales approximately linearly with this parameter.
/// </param>
/// <param name="maxThreads">
/// The maximum number of threads to spawn to derive the key.
/// This is limited by the <paramref name="parallel"/> value.
/// <c>null</c> will use as many threads as possible.
/// </param>
/// <returns>The derived key stream.</returns>
public static Pbkdf2 GetStream(byte[] key, byte[] salt,
int cost, int blockSize, int parallel, int? maxThreads)
{
byte[] B = GetEffectivePbkdf2Salt(key, salt, cost, blockSize, parallel, maxThreads);
Pbkdf2 kdf = new Pbkdf2(new HMACSHA256(key), B, 1);
Security.Clear(B); return kdf;
}
