public Rc4RandomGenerator(IBuffer key)
{
if (key == null)
throw new ArgumentNullException("key");
_state = new byte[256];
var keyLength = key.Length;
for (uint w = 0; w < 256; ++w)
_state[w] = (byte)w;
unchecked
{
byte j = 0;
uint keyIndex = 0;
for (uint w = 0; w < 256; ++w) // Key setup
{
j += (byte)(_state[w] + key.GetByte(keyIndex));
var temp = _state[0];
_state[0] = _state[j];
_state[j] = temp;
++keyIndex;
if (keyIndex >= keyLength)
keyIndex = 0;
}
}
GetRandomBytes(512);
}
/// <summary>
/// Parse the headers fields.
/// </summary>
/// <param name="input">The input stream.</param>
/// <param name="buffer">The header bytes reader.</param>
/// <returns>The file headers.</returns>
private static async Task<FileHeaders> GetHeaders(
IInputStream input, IBuffer buffer)
{
var result = new FileHeaders();
while (true)
{
buffer = await input.ReadAsync(buffer, 3);
var field = (HeaderFields)buffer.GetByte(0);
var size = BitConverter.ToUInt16(buffer.ToArray(1, 2), 0);
if (size > 0)
buffer = await input.ReadAsync(buffer, size);
switch (field)
{
case HeaderFields.EndOfHeader:
return result;
case HeaderFields.CompressionFlags:
result.UseGZip = buffer.GetByte(0) == 1;
break;
case HeaderFields.EncryptionIV:
result.EncryptionIV = buffer
.ToArray().AsBuffer();
break;
case HeaderFields.MasterSeed:
result.MasterSeed = buffer
.ToArray().AsBuffer();
break;
case HeaderFields.StreamStartBytes:
result.StartBytes = buffer
.ToArray().AsBuffer();
break;
case HeaderFields.TransformSeed:
result.TransformSeed = buffer
.ToArray().AsBuffer();
break;
case HeaderFields.TransformRounds:
result.TransformRounds = BitConverter.ToUInt64(
buffer.ToArray(), 0);
break;
case HeaderFields.ProtectedStreamKey:
result.ProtectedStreamKey = buffer
.ToArray().AsBuffer();
break;
case HeaderFields.InnerRandomStreamID:
result.RandomAlgorithm = (CrsAlgorithm)
BitConverter.ToUInt32(buffer.ToArray(), 0);
break;
}
}
}
