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using System;
using Org.BouncyCastle.Crypto.Parameters;
namespace Org.BouncyCastle.Crypto.Macs
{
public class VmpcMac
: IMac
{
private byte g;
private byte n = 0;
private byte[] P = null;
private byte s = 0;
private byte[] T;
private byte[] workingIV;
private byte[] workingKey;
private byte x1, x2, x3, x4;
public virtual int DoFinal(byte[] output, int outOff)
{
// Execute the Post-Processing Phase
for (int r = 1; r < 25; r++)
{
s = P[(s + P[n & 0xff]) & 0xff];
x4 = P[(x4 + x3 + r) & 0xff];
x3 = P[(x3 + x2 + r) & 0xff];
x2 = P[(x2 + x1 + r) & 0xff];
x1 = P[(x1 + s + r) & 0xff];
T[g & 0x1f] = (byte) (T[g & 0x1f] ^ x1);
T[(g + 1) & 0x1f] = (byte) (T[(g + 1) & 0x1f] ^ x2);
T[(g + 2) & 0x1f] = (byte) (T[(g + 2) & 0x1f] ^ x3);
T[(g + 3) & 0x1f] = (byte) (T[(g + 3) & 0x1f] ^ x4);
g = (byte) ((g + 4) & 0x1f);
byte temp = P[n & 0xff];
P[n & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
n = (byte) ((n + 1) & 0xff);
}
// Input T to the IV-phase of the VMPC KSA
for (int m = 0; m < 768; m++)
{
s = P[(s + P[m & 0xff] + T[m & 0x1f]) & 0xff];
byte temp = P[m & 0xff];
P[m & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
}
// Store 20 new outputs of the VMPC Stream Cipher input table M
byte[] M = new byte[20];
for (int i = 0; i < 20; i++)
{
s = P[(s + P[i & 0xff]) & 0xff];
M[i] = P[(P[(P[s & 0xff]) & 0xff] + 1) & 0xff];
byte temp = P[i & 0xff];
P[i & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
}
Array.Copy(M, 0, output, outOff, M.Length);
Reset();
return M.Length;
}
public virtual string AlgorithmName
{
get { return "VMPC-MAC"; }
}
public virtual int GetMacSize()
{
return 20;
}
public virtual void Init(ICipherParameters parameters)
{
if (!(parameters is ParametersWithIV))
throw new ArgumentException("VMPC-MAC Init parameters must include an IV", "parameters");
ParametersWithIV ivParams = (ParametersWithIV) parameters;
KeyParameter key = (KeyParameter) ivParams.Parameters;
if (!(ivParams.Parameters is KeyParameter))
throw new ArgumentException("VMPC-MAC Init parameters must include a key", "parameters");
this.workingIV = ivParams.GetIV();
if (workingIV == null || workingIV.Length < 1 || workingIV.Length > 768)
throw new ArgumentException("VMPC-MAC requires 1 to 768 bytes of IV", "parameters");
this.workingKey = key.GetKey();
Reset();
}
private void initKey(byte[] keyBytes, byte[] ivBytes)
{
s = 0;
P = new byte[256];
for (int i = 0; i < 256; i++)
{
P[i] = (byte) i;
}
for (int m = 0; m < 768; m++)
{
s = P[(s + P[m & 0xff] + keyBytes[m % keyBytes.Length]) & 0xff];
byte temp = P[m & 0xff];
P[m & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
}
for (int m = 0; m < 768; m++)
{
s = P[(s + P[m & 0xff] + ivBytes[m % ivBytes.Length]) & 0xff];
byte temp = P[m & 0xff];
P[m & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
}
n = 0;
}
public virtual void Reset()
{
initKey(this.workingKey, this.workingIV);
g = x1 = x2 = x3 = x4 = n = 0;
T = new byte[32];
for (int i = 0; i < 32; i++)
{
T[i] = 0;
}
}
public virtual void Update(byte input)
{
s = P[(s + P[n & 0xff]) & 0xff];
byte c = (byte) (input ^ P[(P[(P[s & 0xff]) & 0xff] + 1) & 0xff]);
x4 = P[(x4 + x3) & 0xff];
x3 = P[(x3 + x2) & 0xff];
x2 = P[(x2 + x1) & 0xff];
x1 = P[(x1 + s + c) & 0xff];
T[g & 0x1f] = (byte) (T[g & 0x1f] ^ x1);
T[(g + 1) & 0x1f] = (byte) (T[(g + 1) & 0x1f] ^ x2);
T[(g + 2) & 0x1f] = (byte) (T[(g + 2) & 0x1f] ^ x3);
T[(g + 3) & 0x1f] = (byte) (T[(g + 3) & 0x1f] ^ x4);
g = (byte) ((g + 4) & 0x1f);
byte temp = P[n & 0xff];
P[n & 0xff] = P[s & 0xff];
P[s & 0xff] = temp;
n = (byte) ((n + 1) & 0xff);
}
public virtual void BlockUpdate(byte[] input, int inOff, int len)
{
if ((inOff + len) > input.Length)
throw new DataLengthException("input buffer too short");
for (int i = 0; i < len; i++)
{
Update(input[i]);
}
}
}
}
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