/// <summary>
/// Performs an Expensive Key Schedule (EKS) Blowfish key expansion and
/// creates a Blowfish cipher using the result. Flags may modify the key expansion.
/// </summary>
/// <param name="key">
/// The key. This must be between 1 and 72 bytes.
/// Unlike <see cref="BlowfishCrypter"/>, this method does NOT automatically add a null byte to the key.
/// </param>
/// <param name="salt">The salt. This must be 16 bytes.</param>
/// <param name="cost">
/// The expansion cost. This is a value between 4 and 31,
/// specifying the logarithm of the number of iterations.
/// </param>
/// <param name="flags">Flags modifying the key expansion.</param>
/// <returns>A Blowfish cipher.</returns>
public static BlowfishCipher CreateEks(byte[] key, byte[] salt, int cost,
EksBlowfishKeyExpansionFlags flags)
{
Check.Length("key", key, 1, 72);
Check.Length("salt", salt, 16, 16);
Check.Range("cost", cost, 4, 31);
BlowfishCipher fish = new BlowfishCipher(null, null);
fish.ExpandKey(key, salt, flags);
for (uint i = 1u << cost; i > 0; i--)
{
fish.ExpandKey(key, _zeroSalt, flags);
fish.ExpandKey(salt, _zeroSalt, EksBlowfishKeyExpansionFlags.None);
}
return(fish);
}
/// <summary>
/// Creates a Blowfish cipher using the provided key.
/// </summary>
/// <param name="key">The Blowfish key. This must be between 4 and 56 bytes.</param>
/// <returns>A Blowfish cipher.</returns>
public static BlowfishCipher Create(byte[] key)
{
Check.Length("key", key, 4, 56);
BlowfishCipher fish = new BlowfishCipher(null, null);
fish.ExpandKey(key, _zeroSalt, EksBlowfishKeyExpansionFlags.None);
return(fish);
}