/// <summary>
/// adapted from ethereumJ
/// </summary>
private byte[] UpdateMac(KeccakDigest mac, byte[] seed, int offset, byte[] output, int outOffset, bool egress)
{
byte[] aesBlock = new byte[mac.GetDigestSize()];
DoFinalNoReset(mac, aesBlock, 0);
// TODO: check if need to make a new one each time
MakeMacCipher().ProcessBlock(aesBlock, 0, aesBlock, 0);
// Note that although the mac digest size is 32 bytes, we only use 16 bytes in the computation
int length = 16;
for (int i = 0; i < length; i++)
{
aesBlock[i] ^= seed[i + offset];
}
mac.BlockUpdate(aesBlock, 0, length);
byte[] result = new byte[mac.GetDigestSize()];
DoFinalNoReset(mac, result, 0);
if (egress)
{
Array.Copy(result, 0, output, outOffset, length);
}
else
{
bool isMacSame = true;
for (int i = 0; i < length; i++)
{
if (output[i + outOffset] != result[i])
{
isMacSame = false;
break;
}
}
if (!isMacSame)
{
throw new IOException($"MAC mismatch from {_remoteNodeId.ToFullString()}");
}
}
return(result);
}
