public byte[] ComputeHash(byte[] data)
{
byte[] ipad = new byte[64];
byte[] opad = new byte[64];
var hash = new Sha256();
Array.Copy(_key, ipad, _key.Length);
Array.Copy(_key, opad, _key.Length);
for (int i = 0; i < 64 ; ++i)
{
ipad[i] ^= 0x36;
opad[i] ^= 0x5c;
}
hash.AddData(ipad, 0, (uint)ipad.Length);
if (data.Length>0)
hash.AddData(data, 0, (uint)data.Length);
var ipadHash = hash.GetHash();
hash = new Sha256();
hash.AddData(opad, 0, (uint)opad.Length);
hash.AddData(ipadHash, 0, (uint)ipadHash.Length);
return hash.GetHash();
}
public static byte[] HashFile(Stream fs)
{
Sha256 sha = new Sha256();
byte[] buf = new byte[8196];
uint bytes_read;
do
{
bytes_read = (uint)fs.Read(buf, 0, buf.Length);
if (bytes_read == 0)
break;
sha.AddData(buf, 0, bytes_read);
}
while (bytes_read == 8196);
return sha.GetHash();
}
private void Initialize(byte[] keyData)
{
Array.Clear(_key,0,_key.Length);
// If the key is too long, use the hash of the key
if (keyData.Length>_key.Length)
{
var hashAlgo = new Sha256();
hashAlgo.AddData(keyData, 0, (uint)keyData.Length);
keyData = hashAlgo.GetHash();
}
Array.Copy(keyData, _key, keyData.Length);
}