public static HMAC GetMac(HMACType func, byte[] key)
{
switch (func)
{
case HMACType.SHA1:
return(new HMACSHA1(key));
case HMACType.SHA256:
return(new HMACSHA256(key));
case HMACType.SHA384:
return(new HMACSHA384(key));
case HMACType.SHA512:
return(new HMACSHA512(key));
default:
throw new ArgumentOutOfRangeException("func", func, null);
}
}
public HMACTypeHandler(HMACType _type)
{
switch (_type)
{
case HMACType.MD5:
hmac = new HMACMD5();
break;
case HMACType.SHA1:
hmac = new HMACSHA1();
break;
case HMACType.SHA2:
hmac = new HMACSHA256();
break;
case HMACType.SHA3:
hmac = new HMACSHA384();
break;
default:
break;
}
}
protected virtual bool ExplicitHasValue()
{
return(SecretKey != null && CodeDigits > 0 && HMACType.IsDefined() && Period > 0);
}
public static byte[] GenerateDerivedKey(int keySize, byte[] password, byte[] salt, int iterations, HMACType func)
{
using (var mac = GetMac(func, password))
{
var hLen = mac.HashSize / 8;
var l = (keySize + hLen - 1) / hLen;
var outBytes = new byte[l * hLen];
byte[] p = new byte[salt.Length + 4];
Array.Copy(salt, 0, p, 0, salt.Length);
for (int i = 1; i <= l; i++)
{
p[p.Length - 4] = (byte)((uint)i >> 24);
p[p.Length - 3] = (byte)((uint)i >> 16);
p[p.Length - 2] = (byte)((uint)i >> 8);
p[p.Length - 1] = (byte)((uint)i >> 0);
byte[] state = new HMACSHA512(password).ComputeHash(p);
Array.Copy(state, 0, outBytes, (i - 1) * hLen, state.Length);
for (int count = 1; count != iterations; count++)
{
state = new HMACSHA512(password).ComputeHash(state);
for (int j = 0; j != state.Length; j++)
{
outBytes[(i - 1) * hLen + j] ^= state[j];
}
}
}
byte[] output = new byte[keySize];
Buffer.BlockCopy(outBytes, 0, output, 0, keySize);
return(output);
}
}
