/// <summary>
/// Construct a new cryptographically secure random stream object.
/// </summary>
/// <param name="genAlgorithm">Algorithm to use.</param>
/// <param name="pbKey">Initialization key. Must not be <c>null</c> and
/// must contain at least 1 byte.</param>
/// <exception cref="System.ArgumentNullException">Thrown if the
/// <paramref name="pbKey" /> parameter is <c>null</c>.</exception>
/// <exception cref="System.ArgumentException">Thrown if the
/// <paramref name="pbKey" /> parameter contains no bytes or the
/// algorithm is unknown.</exception>
public CryptoRandomStream(CrsAlgorithm genAlgorithm, byte[] pbKey)
{
if (pbKey == null)
throw new ArgumentNullException("pbKey");
_algorithm = genAlgorithm;
var uKeyLen = (uint)pbKey.Length;
if (uKeyLen == 0)
throw new ArgumentException();
switch (genAlgorithm)
{
case CrsAlgorithm.ArcFourVariant:
_pbState = new byte[256];
for (uint w = 0; w < 256; ++w)
_pbState[w] = (byte)w;
unchecked
{
byte j = 0, t;
uint inxKey = 0;
for (uint w = 0; w < 256; ++w) // Key setup
{
j += (byte)(_pbState[w] + pbKey[inxKey]);
t = _pbState[0]; // Swap entries
_pbState[0] = _pbState[j];
_pbState[j] = t;
++inxKey;
if (inxKey >= uKeyLen) inxKey = 0;
}
}
GetRandomBytes(512); // Increases security, see cryptanalysis
break;
case CrsAlgorithm.Salsa20:
{
var sha256 = new SHA256Managed();
var pbKey32 = sha256.ComputeHash(pbKey);
var pbIV = new byte[]
{
0xE8, 0x30, 0x09, 0x4B,
0x97, 0x20, 0x5D, 0x2A
}; // Unique constant
_salsa20 = new Salsa20Cipher(pbKey32, pbIV);
}
break;
default:
throw new ArgumentException();
}
}
/// <summary>
/// Construct a new cryptographically secure random stream object.
/// </summary>
/// <param name="genAlgorithm">Algorithm to use.</param>
/// <param name="pbKey">Initialization key. Must not be <c>null</c> and
/// must contain at least 1 byte.</param>
/// <exception cref="System.ArgumentNullException">Thrown if the
/// <paramref name="pbKey" /> parameter is <c>null</c>.</exception>
/// <exception cref="System.ArgumentException">Thrown if the
/// <paramref name="pbKey" /> parameter contains no bytes or the
/// algorithm is unknown.</exception>
public CryptoRandomStream(CrsAlgorithm genAlgorithm, byte[] pbKey)
{
if (pbKey == null)
{
throw new ArgumentNullException("pbKey");
}
_algorithm = genAlgorithm;
var uKeyLen = (uint)pbKey.Length;
if (uKeyLen == 0)
{
throw new ArgumentException();
}
switch (genAlgorithm)
{
case CrsAlgorithm.ArcFourVariant:
_pbState = new byte[256];
for (uint w = 0; w < 256; ++w)
{
_pbState[w] = (byte)w;
}
unchecked
{
byte j = 0, t;
uint inxKey = 0;
for (uint w = 0; w < 256; ++w) // Key setup
{
j += (byte)(_pbState[w] + pbKey[inxKey]);
t = _pbState[0]; // Swap entries
_pbState[0] = _pbState[j];
_pbState[j] = t;
++inxKey;
if (inxKey >= uKeyLen)
{
inxKey = 0;
}
}
}
GetRandomBytes(512); // Increases security, see cryptanalysis
break;
case CrsAlgorithm.Salsa20:
{
var sha256 = new SHA256Managed();
var pbKey32 = sha256.ComputeHash(pbKey);
var pbIV = new byte[]
{
0xE8, 0x30, 0x09, 0x4B,
0x97, 0x20, 0x5D, 0x2A
}; // Unique constant
_salsa20 = new Salsa20Cipher(pbKey32, pbIV);
}
break;
default:
throw new ArgumentException();
}
}
