/// <summary>
/// Initialises a stream cipher from cipher configuration DTO. Used by constructor.
/// </summary>
private static ICipherWrapper InitStreamCipher(bool encrypting, CipherConfiguration config, byte[] key, out int maxDelta)
{
var streamConfigWrapper = new StreamCipherConfigurationWrapper(config);
if (key.Length != streamConfigWrapper.KeySizeBytes)
{
throw new ArgumentException("Key is not of the length declared in the cipher configuration.",
"key");
}
StreamCipherEngine streamCipher;
try {
streamCipher = CipherFactory.CreateStreamCipher(streamConfigWrapper.GetStreamCipher());
streamCipher.Init(encrypting, key, streamConfigWrapper.GetNonce());
} catch (Exception e) {
throw new ConfigurationInvalidException("Configuration of stream cipher is invalid.",
e.InnerException);
}
// This should always be 0, but we'll do it anyway...
maxDelta = Athena.Cryptography.StreamCiphers[streamCipher.Identity].MaximumOutputSizeDifference(encrypting);
return(new StreamCipherWrapper(encrypting, streamCipher, strideIncreaseFactor: 2));
}
/// <summary>
/// Initialises a block cipher from cipher configuration DTO. Used by constructor.
/// </summary>
private static ICipherWrapper InitBlockCipher(bool encrypting, CipherConfiguration config, byte[] key, out int maxDelta)
{
var blockConfigWrapper = new BlockCipherConfigurationWrapper(config);
if (key.Length != blockConfigWrapper.KeySizeBytes)
{
throw new ArgumentException("Key is not of the length declared in the cipher configuration.",
"key");
}
BlockCipherBase blockCipherPrimitive = CipherFactory.CreateBlockCipher(blockConfigWrapper.GetBlockCipher(),
blockConfigWrapper.GetBlockSizeBits());
// Overlay the cipher with the mode of operation
BlockCipherModeBase blockCipher;
try {
blockCipher = CipherFactory.OverlayBlockCipherWithMode(blockCipherPrimitive, blockConfigWrapper.Mode);
} catch (Exception e) {
throw new ConfigurationInvalidException(
"Configuration of block cipher mode of operation is invalid.", e.InnerException);
}
IBlockCipherPadding padding = null;
BlockCipherPadding paddingEnum = blockConfigWrapper.GetPadding();
if (paddingEnum != BlockCipherPadding.None)
{
padding = CipherFactory.CreatePadding(paddingEnum);
padding.Init(StratCom.EntropySupplier);
}
maxDelta = Athena.Cryptography.BlockCiphers[blockCipherPrimitive.Identity].MaximumOutputSizeDifference(encrypting);
blockCipher.Init(encrypting, key, blockConfigWrapper.GetInitialisationVector());
return(new BlockCipherWrapper(encrypting, blockCipher, padding));
}