/// <summary>
/// Initializes the Skein hash instance.
/// </summary>
/// <param name="stateSize">The internal state size of the hash in bits.
/// Supported values are 256, 512, and 1024.</param>
/// <param name="outputSize">The output size of the hash in bits.
/// Output size must be divisible by 8 and greater than zero.</param>
public Skein(int stateSize, int outputSize)
{
if (outputSize <= 0)
{
throw new CryptographicException("Output bit size must be greater than zero.");
}
if (outputSize % 8 != 0)
{
throw new CryptographicException("Output bit size must be divisible by 8.");
}
cipherStateBits = stateSize;
cipherStateBytes = stateSize / 8;
cipherStateWords = stateSize / 64;
HashSizeValue = outputSize;
outputBytes = (outputSize + 7) / 8;
cipher = ThreefishCipher.CreateCipher(stateSize);
if (cipher == null)
{
throw new CryptographicException("Unsupported state size.");
}
inputBuffer = new byte[cipherStateBytes];
cipherInput = new ulong[cipherStateWords];
state = new ulong[cipherStateWords];
UbiParameters = new UbiTweak();
Configuration = new SkeinConfig(this);
Configuration.SetSchema(83, 72, 65, 51); // "SHA3"
Configuration.SetVersion(1);
Configuration.GenerateConfiguration();
Initialize();
}
public void GenerateConfiguration()
{
var cipher = ThreefishCipher.CreateCipher(stateSize);
var tweak = new UbiTweak();
tweak.StartNewBlockType(UbiType.Config);
tweak.IsFinalBlock = true;
tweak.BitsProcessed = 32;
cipher.SetTweak(tweak.Tweak);
cipher.Encrypt(ConfigString, ConfigValue);
ConfigValue[0] ^= ConfigString[0];
ConfigValue[1] ^= ConfigString[1];
ConfigValue[2] ^= ConfigString[2];
}
