/// <summary>
/// expands R from 20 to 30 bit
/// </summary>
public static ByteUInt ExpandR(ByteUInt R)
{
uint tmp;
// Set bits right to left, starting here:
tmp = 0x00100000; // and set bits form 0B-0D(0-3)
for (var i = 0; i < 10; i++)
{
if ((R.FullUint & expandRTable[i]) != 0)
{
R.FullUint |= tmp;
}
tmp <<= 1;
}
return(R);
}
// Read from: sboxresult
// write to: L
public static ByteUInt DoPbox(ByteUInt sBoxResult)
{
uint tmp;
ByteUInt L = new ByteUInt();
L.FullUint = 0xFF000000; // clear 12-14
tmp = 0x00000001; // and set bits from 1C-1E (result from F)
for (var i = 0; i < 20; i++)
{
if ((sBoxResult.FullUint & mUintArrBitPattern20[i]) != 0)
{
L.FullUint |= tmp;
}
tmp <<= 1;
}
return(L);
}
/// <summary>
/// Compress 40 bit time to 30 bit key (stored in L')
/// </summary>
private ByteUInt CompressKey(byte timeH, uint timeL)
{
ByteUInt L_ = new ByteUInt();
uint tmp;
L_.FullUint = 0; // clear 12-15
tmp = 0x00000001; // and set bits from 16-1A (time)
for (var i = 0; i < 30; i++)
{
if ((timeL & timeCompression1[i]) != 0 ||
(timeH & timeCompression2[i]) != 0)
{
L_.FullUint |= tmp;
}
tmp <<= 1;
}
return(L_);
}
public static ByteUInt ExpandR(ByteUInt R)
{
uint tmp;
Console.Write("{ " + R.FullUint + ", ");
R.FullUint &= 0x000FFFFF; // clear 0D(4-7),0E
tmp = 0x00100000; // and set bits form 0B-0D(0-3)
for (var i = 0; i < 10; i++)
{
if ((R.FullUint & mUintArrBitPattern12[i]) != 0)
{
R.FullUint |= tmp;
}
tmp <<= 1;
}
Console.WriteLine(R.FullUint + "},");
return(R);
}
/// <summary>
/// DECRYPTION
/// </summary>
/// <param name="cipher"></param>
/// <param name="key"></param>
/// <returns></returns>
private unsafe byte[] Decrypt(byte *cipher, byte *key)
{
var container = new DataContainer();
var plain = new byte[5];
CopyTimeToByteUint(cipher, key, ref container);
// OUTER LOOP 1 (16 Rounds)
for (var round = 16; round > 0; round--)
{
Console.WriteLine($"Round {round}: L={container.L.FullUint:X}, R={container.R.FullUint:X}");
Console.WriteLine($"timeH=0x{container.timeH:x}, timeL=0x{container.timeL:x}");
ShiftTimeRight(round, ref container);
Console.WriteLine($"Rotated Time. timeH=0x{container.timeH:x}, timeL=0x{container.timeL:x}");
ByteUInt compressedKey = CompressKey(container.timeH, container.timeL);
Console.WriteLine($"Compressed key: 0x{compressedKey.FullUint:x}");
uint expandedR = ExpandR(container.R).FullUint;
Console.WriteLine($"Expanded R: 0x{expandedR:x}");
uint sboxInput = compressedKey.FullUint ^ expandedR;
uint bit6Group = build6bitGroups(sboxInput);
Console.WriteLine($"Built 6bit groups: {bit6Group:x}");
uint sboxresult = Sbox(bit6Group);
Console.WriteLine($"S Box result: {sboxresult:x}");
uint pboxResult = Pbox(sboxresult);
Console.WriteLine($"Applied f: {pboxResult:x}");
pboxResult ^= container.L.FullUint;
// L = R
container.L.FullUint = container.R.FullUint;
// R = L'
container.R.FullUint = pboxResult;
}
Console.WriteLine($"Decrypted R = {container.R.FullUint}, L = {container.L.FullUint}");
// 4 bits from R get moved to L
container.R.FullUint <<= 4;
container.L.Byte2 &= 0x0F;
container.L.Byte2 |= (byte)(container.R.Byte0 & 0xF0);
plain[0] = container.L.Byte0;
plain[1] = container.L.Byte1;
plain[2] = container.L.Byte2;
plain[3] = container.R.Byte1;
plain[4] = container.R.Byte2;
for (int i = 0; i < 5; i++)
{
Console.WriteLine($"plain[{i}] = 0x{plain[i]:X}");
}
return(plain);
}
public static ByteUInt DoSbox(ByteUInt L)
{
byte tmp, helper; //mByteR1B;
ByteUInt result = new ByteUInt();
result.FullUint = 0;
helper = L.Byte3; // R1B = R15;
L.Byte3 = L.Byte2; // R15 = R14
// INNER LOOP
for (var i = 5; i > 0; i--)
{
if ((i & 1) == 0) // round 4,2
{
tmp = (byte)(L.Byte0 >> 4); // swap R12
tmp |= (byte)((L.Byte0 & 0x0f) << 4);
L.Byte0 = tmp;
}
L.Byte3 &= 0xF0; // set R1C
tmp = (byte)((L.Byte0 & 0x0F) | L.Byte3);
if ((i & 4) != 0)
{
tmp = mByteArrLookupTable1C_1[tmp & 0x3F];
}
if ((i & 2) != 0)
{
tmp = mByteArrLookupTable1C_2[tmp & 0x3F];
}
else if (i == 1)
{
tmp = mByteArrLookupTable1C_3[tmp & 0x3F];
}
if ((i & 1) != 0)
{
result.Byte0 = (byte)(tmp & 0x0F);
}
else
{
result.Byte0 |= (byte)(tmp & 0xF0);
}
if ((i & 1) == 0) // copy 14->13->12, 1C->1E->1D
{
tmp = L.Byte3;
L.FullUint >>= 8;
L.Byte3 = tmp;
result.FullUint <<= 8;
}
L.Byte3 >>= 1; // rotate R1B>R15 twice
if ((helper & 1) != 0)
{
L.Byte3 |= 0x80;
}
helper >>= 1;
L.Byte3 >>= 1;
if ((helper & 1) != 0)
{
L.Byte3 |= 0x80;
}
helper >>= 1;
} // end of inner loop
return(result);
}
