/// <summary>
/// Creates a Poly1305 primitive using a symmetric block cipher primitive (cipher must have a block size of 128 bits).
/// If salt is used, it is applied as: salt||message, where || is concatenation.
/// </summary>
/// <param name="cipherEnum">Cipher primitive to use as the basis for the Poly1305 construction.</param>
/// <param name="key">Cryptographic key to use in the MAC operation.</param>
/// <param name="nonce">Initialisation vector/nonce. Required.</param>
/// <param name="salt">Cryptographic salt to use in the MAC operation, if any.</param>
/// <returns>Pre-initialised Poly1305 MAC primitive as a <see cref="IMac" />.</returns>
public static IMac CreatePoly1305Primitive(BlockCipher cipherEnum, byte[] key, byte[] nonce, byte[] salt = null)
{
if (Athena.Cryptography.BlockCiphers[cipherEnum].DefaultBlockSizeBits != 128)
{
throw new NotSupportedException();
}
var macObj = new Poly1305Mac(CipherFactory.CreateBlockCipher(cipherEnum));
macObj.Init(key, nonce);
if (salt.IsNullOrZeroLength() == false)
{
macObj.BlockUpdate(salt, 0, salt.Length);
}
return(macObj);
}
/// <summary>
/// Creates a CMAC primitive using a symmetric block cipher primitive configured with default block size.
/// Default block sizes (and so, output sizes) can be found by querying <see cref="Athena" />.
/// </summary>
/// <param name="cipherEnum">
/// Cipher primitive to use as the basis for the CMAC construction. Block size must be 64 or 128
/// bits.
/// </param>
/// <param name="key">Cryptographic key to use in the MAC operation.</param>
/// <param name="salt">Cryptographic salt to use in the MAC operation, if any.</param>
/// <returns>Pre-initialised CMAC primitive as a <see cref="IMac" />.</returns>
public static IMac CreateCmacPrimitive(BlockCipher cipherEnum, byte[] key, byte[] salt = null)
{
int?defaultBlockSize = Athena.Cryptography.BlockCiphers[cipherEnum].DefaultBlockSizeBits;
if (defaultBlockSize != 64 && defaultBlockSize != 128)
{
throw new NotSupportedException("CMAC/OMAC1 only supports ciphers with 64 / 128 bit block sizes.");
}
var macObj = new CMac(CipherFactory.CreateBlockCipher(cipherEnum, null));
macObj.Init(key);
if (salt.IsNullOrZeroLength() == false)
{
macObj.BlockUpdate(salt, 0, salt.Length);
}
return(macObj);
}
