public static byte[] RepeatingKeyXor(byte[] key, byte[] source)
{
if (key == null)
{
throw new ArgumentNullException("key");
}
if (source == null)
{
throw new ArgumentNullException("source");
}
var keyLength = key.Length;
var result = new byte[source.Length];
using (var sourceMs = new MemoryStream(source))
{
using (var destinationMs = new MemoryStream(result))
{
var buffer = new byte[keyLength];
int read;
while ((read = sourceMs.Read(buffer, 0, buffer.Length)) > 0)
{
byte[] keyBytesToUse;
byte[] bufferToUse;
if (read != keyLength)
{
keyBytesToUse = new byte[read];
Array.Copy(key, keyBytesToUse, read);
bufferToUse = new byte[read];
Array.Copy(buffer, bufferToUse, read);
}
else
{
keyBytesToUse = key;
bufferToUse = buffer;
}
var currentChunk = Challenge2.Xor(keyBytesToUse, bufferToUse);
destinationMs.Write(currentChunk, 0, read);
}
}
}
return(result);
}
public static int HammingDistance(byte[] valueA, byte[] valueB)
{
if (valueA == null)
{
throw new ArgumentNullException("valueA");
}
if (valueB == null)
{
throw new ArgumentNullException("valueB");
}
if (valueA.Length != valueB.Length)
{
throw new ArgumentOutOfRangeException("valueA", "Both values must be the same length.");
}
var xorValue = Challenge2.Xor(valueA, valueB);
return(xorValue.Sum(x => SetBitCountMap[x]));
}