/// <summary>
/// Create a configuration for a block cipher.
/// </summary>
/// <param name="cipher">Block cipher to use.</param>
/// <param name="mode">Mode of operation for the cipher.</param>
/// <param name="padding">Padding scheme to use with the mode, where necessary (e.g. CBC).</param>
/// <param name="keySize">Key size to use, in bits.</param>
/// <param name="blockSize">Cipher block size to use, in bits.</param>
/// <returns>Block cipher configuration DTO.</returns>
public static CipherConfiguration CreateBlockCipherConfiguration(BlockCipher cipher,
BlockCipherMode mode, BlockCipherPadding padding, int?keySize = null, int?blockSize = null)
{
var config = new CipherConfiguration {
Type = CipherType.Block
};
// Set the key size
int keySizeNonNull = keySize ?? Athena.Cryptography.BlockCiphers[cipher].DefaultKeySizeBits;
if (keySize == null || Athena.Cryptography.BlockCiphers[cipher].AllowableKeySizesBits.Contains(keySizeNonNull))
{
config.KeySizeBits = keySizeNonNull;
}
else
{
throw new CipherKeySizeException(cipher, keySizeNonNull);
}
// Set the block size
int blockSizeNonNull = blockSize ?? Athena.Cryptography.BlockCiphers[cipher].DefaultBlockSizeBits;
if (blockSize == null ||
Athena.Cryptography.BlockCiphers[cipher].AllowableBlockSizesBits.Contains(blockSizeNonNull))
{
config.BlockSizeBits = blockSizeNonNull;
}
else
{
throw new BlockSizeException(cipher, blockSizeNonNull);
}
// Set the mode
if (Athena.Cryptography.BlockCipherModes[mode].PaddingRequirement == PaddingRequirement.Always &&
padding == BlockCipherPadding.None)
{
throw new ArgumentException(mode +
" mode must be used with padding or errors will occur when plaintext length is not equal to or a multiple of the block size.");
}
config.ModeName = mode.ToString();
config.PaddingName = padding.ToString();
config.CipherName = cipher.ToString();
config.InitialisationVector = new byte[config.BlockSizeBits.Value / 8];
StratCom.EntropySupplier.NextBytes(config.InitialisationVector);
return(config);
}
/// <summary>
/// Scheme utillised to 'pad' blocks to full size where required.
/// What any unused space in a block is filled with.
/// Set to empty if using block cipher in streaming mode.
/// </summary>
public void SetPadding(BlockCipherPadding value)
{
RawConfiguration.PaddingName = value.ToString();
}