private byte[] GetSecondRoundResult(byte[] firstRoundResult, byte[] subKey)
{
var nibbled = Aes16Helper.NibbleSubstitution(firstRoundResult);
var secondFourBitsOfFirstByte = (byte)(nibbled[0] & 0b00001111);
var secondFourBitsOfSecondByte = (byte)(nibbled[1] & 0b00001111);
var newFirstByte = (byte)((nibbled[0] & 0b11110000) | secondFourBitsOfSecondByte);
var newSecondByte = (byte)((nibbled[1] & 0b11110000) | secondFourBitsOfFirstByte);
var shiftedBytes = new[] { newFirstByte, newSecondByte };
return(Aes16Helper.AddRoundKey(shiftedBytes, subKey));
}
private byte[] GetFirstRoundResult(byte[] zeroRoundResult, byte[] roundKey)
{
// Nibble substitution
var nibbled = Aes16Helper.NibbleSubstitution(zeroRoundResult);
// Shift row
var shiftedRowBytes = Aes16Helper.ShiftRow(nibbled);
var mixedBytes = Aes16Helper.MixColumns(shiftedRowBytes);
return(Aes16Helper.AddRoundKey(new[] { mixedBytes[0], mixedBytes[1] }, roundKey));
}