public BitArray[] Generate(BitArray key)
{
if (key.Count != 10)
{
throw new ArgumentException("Key length should be 10 bits");
}
var p10 = SimplifiedDesHelper.P10(key);
var first5Bits = SimplifiedDesHelper.GetBits(p10, 0, 5);
var second5Bits = SimplifiedDesHelper.GetBits(p10, 5, 5);
var first5BitsShifted = SimplifiedDesHelper.LeftShift(first5Bits, 1);
var second5BitsShifted = SimplifiedDesHelper.LeftShift(second5Bits, 1);
var mergedKey = first5BitsShifted.Merge(second5BitsShifted);
var firstSubKey = SimplifiedDesHelper.P8(mergedKey);
var a = SimplifiedDesHelper.LeftShift(first5Bits, 3);
var b = SimplifiedDesHelper.LeftShift(second5Bits, 3);
var mergedKeyAgain = a.Merge(b);
var secondSubKey = SimplifiedDesHelper.P8(mergedKeyAgain);
return(new[] { firstSubKey, secondSubKey });
}
private BitArray F(BitArray bitArray, BitArray key)
{
if (bitArray.Count != 4)
{
throw new ArgumentException("F argument length should be 4 bits");
}
var permuteAndExpand = new BitArray(8)
{
[0] = bitArray[3],
[1] = bitArray[0],
[2] = bitArray[1],
[3] = bitArray[2],
[4] = bitArray[1],
[5] = bitArray[2],
[6] = bitArray[3],
[7] = bitArray[0]
};
var xoredWithKey = permuteAndExpand.NormalXor(key);
var leftPart = SimplifiedDesHelper.GetLeftPart(xoredWithKey);
var rightPart = SimplifiedDesHelper.GetRightPart(xoredWithKey);
var leftPartSboxed = Sbox(leftPart, 1);
var rightPartSboxed = Sbox(rightPart, 2);
return(SimplifiedDesHelper.P4(leftPartSboxed.Merge(rightPartSboxed)));
}
private BitArray Switch(BitArray bitArray)
{
var leftPart = SimplifiedDesHelper.GetLeftPart(bitArray);
var rightPart = SimplifiedDesHelper.GetRightPart(bitArray);
return(rightPart.Merge(leftPart));
}
private BitArray Fk(BitArray afterIp, BitArray key)
{
var left = SimplifiedDesHelper.GetLeftPart(afterIp);
var right = SimplifiedDesHelper.GetRightPart(afterIp);
left = left.NormalXor(F(right, key));
return(left.Merge(right));
}