/// <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();
}
internal ThreefishTransform(byte[] key, byte[] iv, int feedbackSize, ThreefishTransformMode transformMode,
CipherMode cipherMode, PaddingMode paddingMode)
{
this.transformMode = transformMode;
this.cipherMode = cipherMode;
this.paddingMode = paddingMode;
cipherBytes = key.Length;
cipherWords = key.Length / 8;
feedbackBytes = feedbackSize / 8;
// Allocate working blocks now so that we don't have to allocate them
// each time Transform(Final)Block is called
block = new ulong[cipherWords];
tempBlock = new ulong[cipherWords];
streamBytes = new byte[cipherBytes];
depadBuffer = new byte[cipherBytes];
this.iv = new ulong[cipherWords];
GetBytes(iv, 0, this.iv, cipherBytes);
switch (OutputBlockSize)
{
case 256 / 8: cipher = new Threefish256(); break;
case 512 / 8: cipher = new Threefish512(); break;
case 1024 / 8: cipher = new Threefish1024(); break;
default: throw new CryptographicException("Unsupported key/block size.");
}
bool e = transformMode == ThreefishTransformMode.Encrypt;
switch (cipherMode)
{
case CipherMode.ECB:
transformFunc = e ? EcbEncrypt : new TransformFunc(EcbDecrypt);
break;
case CipherMode.CBC:
transformFunc = e ? CbcEncrypt : new TransformFunc(CbcDecrypt);
break;
case CipherMode.OFB:
transformFunc = OfbApplyStream;
break;
case CipherMode.CFB:
transformFunc = e ? CfbEncrypt : new TransformFunc(CfbDecrypt);
break;
default:
throw new CryptographicException("Unsupported cipher mode.");
}
var keyWords = new ulong[cipherWords];
GetBytes(key, 0, keyWords, cipherBytes);
cipher.SetKey(keyWords);
InitializeBlocks();
}
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];
}