public static byte[] GetKeyTokenFromFullKey(this byte[] fullKey) {
var csp = new SHA1CryptoServiceProvider();
byte[] hash = csp.ComputeHash(fullKey);
var token = new byte[8];
for (int i = 0; i < 8; i++) {
token[i] = hash[hash.Length - (i + 1)];
}
return hash;
}