public static void Process(IBlockCipher cipher, MemoryStream data, int off, int len,
byte[] iv, IBlockCipher f8Cipher)
{
F8Context f8ctx = new F8Context();
/*
* Get memory for the derived IV (IV')
*/
f8ctx.ivAccent = new byte[BLKLEN];
/*
* Use the derived IV encryption setup to encrypt the original IV to produce IV'.
*/
f8Cipher.ProcessBlock(iv, 0, f8ctx.ivAccent, 0);
f8ctx.J = 0; // initialize the counter
f8ctx.S = new byte[BLKLEN]; // get the key stream buffer
Arrays.Fill(f8ctx.S, (byte)0);
int inLen = len;
while (inLen >= BLKLEN)
{
ProcessBlock(cipher, f8ctx, data, off, data, off, BLKLEN);
inLen -= BLKLEN;
off += BLKLEN;
}
if (inLen > 0)
{
ProcessBlock(cipher, f8ctx, data, off, data, off, inLen);
}
}
/**
* Encrypt / Decrypt a block using F8 Mode AES algorithm, read len bytes
* data from in at inOff and write the output into out at outOff
*
* @param f8ctx
* F8 encryption context
* @param in
* byte array holding the data to be processed
* @param inOff
* start offset of the data to be processed inside in array
* @param out
* byte array that will hold the processed data
* @param outOff
* start offset of output data in out
* @param len
* length of the input data
*/
public static void ProcessBlock(IBlockCipher cipher, F8Context f8ctx,
MemoryStream _in, int inOff, MemoryStream _out, int outOff, int len)
{
/*
* XOR the previous key stream with IV'
* ( S(-1) xor IV' )
*/
for (int i = 0; i < BLKLEN; i++)
{
f8ctx.S[i] ^= f8ctx.ivAccent[i];
}
/*
* Now XOR (S(n-1) xor IV') with the current counter, then increment
* the counter
*/
f8ctx.S[12] ^= (byte)(f8ctx.J >> 24);
f8ctx.S[13] ^= (byte)(f8ctx.J >> 16);
f8ctx.S[14] ^= (byte)(f8ctx.J >> 8);
f8ctx.S[15] ^= (byte)(f8ctx.J);
f8ctx.J++;
/*
* Now compute the new key stream using AES encrypt
*/
cipher.ProcessBlock(f8ctx.S, 0, f8ctx.S, 0);
/*
* As the last step XOR the plain text with the key stream to produce
* the cipher text.
*/
for (int i = 0; i < len; i++)
{
_in.Position = inOff + i;
var inByte = _in.ReadByte();
_out.Position = outOff + i;
_out.WriteByte((byte)(inByte ^ f8ctx.S[i]));
}
}
