internal override bool Decrypt(int recordType, int version,
byte[] data, ref int off, ref int len)
{
off += 8;
len -= 24;
IO.Enc64be(seq, tmp, 0);
IO.WriteHeader(recordType, version, len, tmp, 8);
IO.Enc64be(13 << 3, tmp, 13);
IO.Enc64be((ulong)len << 3, tmp, 21);
for (int i = 0; i < 16; i++)
{
tag[i] = 0;
}
GHASH.Run(tag, h, tmp, 0, 13);
GHASH.Run(tag, h, data, off, len);
GHASH.Run(tag, h, tmp, 13, 16);
seq++;
Array.Copy(data, off - 8, iv, 4, 8);
bc.CTRRun(iv, 2, data, off, len);
bc.CTRRun(iv, 1, data, off + len, 16);
int z = 0;
for (int i = 0; i < 16; i++)
{
z |= tag[i] ^ data[off + len + i];
}
return(z == 0);
}
internal override void Encrypt(int recordType, int version,
byte[] data, ref int off, ref int len)
{
/*
* Explicit nonce is the encoded sequence number. We
* encrypt the data itself; the counter starts at 2
* (value 1 is for the authentication tag).
*/
IO.Enc64be(seq, data, off - 8);
Array.Copy(data, off - 8, iv, 4, 8);
bc.CTRRun(iv, 2, data, off, len);
/*
* For the authentication tag:
* header = sequence + 5-byte "plain" header
* footer = the two relevant lengths (in bits)
*/
IO.Enc64be(seq, tmp, 0);
IO.WriteHeader(recordType, version, len, tmp, 8);
IO.Enc64be(13 << 3, tmp, 13);
IO.Enc64be((ulong)len << 3, tmp, 21);
/*
* Compute clear authentication tag.
*/
for (int i = 0; i < 16; i++)
{
tag[i] = 0;
}
GHASH.Run(tag, h, tmp, 0, 13);
GHASH.Run(tag, h, data, off, len);
GHASH.Run(tag, h, tmp, 13, 16);
/*
* Copy authentication tag and apply final encryption on it.
*/
Array.Copy(tag, 0, data, off + len, 16);
bc.CTRRun(iv, 1, data, off + len, 16);
/*
* Each record uses one sequence number.
*/
seq++;
/*
* Write encrypted header and return adjusted offset/length.
*/
off -= 13;
len += 24;
IO.WriteHeader(recordType, version, len, data, off);
len += 5;
}
