public void ShiftLeftWrapped(BLOCK8BYTE s, int bitShift)
{
// this shift is only applied to the first 32 bits, and parity bit is ignored
// Declaration of local variables
int byteOffset;
bool bit;
// Copy byte and shift regardless
for (byteOffset = 0; byteOffset < 4; byteOffset++)
_data[byteOffset] = Convert.ToByte((s._data[byteOffset] << bitShift) & 0xFF);
// if shifting by 1...
if (bitShift == 1)
{
// repair bits on right of BYTE
for (byteOffset = 0; byteOffset < 3; byteOffset++)
{
// get repairing bit offsets
bit = s.GetBit(byteOffset + 1, 7);
this.SetBit(byteOffset, 1, bit);
}
// wrap around the final bit
this.SetBit(3, 1, s.GetBit(0, 7));
}
else if (bitShift == 2)
{
// repair bits on right of BYTE
for (byteOffset = 0; byteOffset < 3; byteOffset++)
{
// get repairing bit offsets
bit = s.GetBit(byteOffset + 1, 7);
this.SetBit(byteOffset, 2, bit);
bit = s.GetBit(byteOffset + 1, 6);
this.SetBit(byteOffset, 1, bit);
}
// wrap around the final bit
this.SetBit(3, 2, s.GetBit(0, 7));
this.SetBit(3, 1, s.GetBit(0, 6));
}
else
Debug.Assert(false);
}
protected KeySet ExpandKey(byte[] key, int offset)
{
//
// Expand an 8 byte DES key into a set of permuted keys
//
// Declare return variable
KeySet ftmp = new KeySet();
// Declaration of local variables
int arrayOffset, permOffset, byteOffset, bitOffset;
bool bBit;
// Put key into an 8-bit block
BLOCK8BYTE k = new BLOCK8BYTE();
k.Set(key, offset);
// Permutate Kp with PC1
BLOCK8BYTE kp = new BLOCK8BYTE();
for (arrayOffset = 0; arrayOffset < DESTables.PC1.Length; arrayOffset++)
{
// Get permute offset
permOffset = DESTables.PC1[arrayOffset];
permOffset--;
// Get and set bit
kp.SetBit(
BitAddressToByteOffset(arrayOffset, 7),
BitAddressToBitOffset(arrayOffset, 7),
k.GetBit(
BitAddressToByteOffset(permOffset, 8),
BitAddressToBitOffset(permOffset, 8)
)
);
}
// Create 17 blocks of C and D from Kp
BLOCK8BYTE[] kpCn = new BLOCK8BYTE[17];
BLOCK8BYTE[] kpDn = new BLOCK8BYTE[17];
for (arrayOffset = 0; arrayOffset < 17; arrayOffset++)
{
kpCn[arrayOffset] = new BLOCK8BYTE();
kpDn[arrayOffset] = new BLOCK8BYTE();
}
for (arrayOffset = 0; arrayOffset < 32; arrayOffset++)
{
// Set bit in KpCn
byteOffset = BitAddressToByteOffset(arrayOffset, 8);
bitOffset = BitAddressToBitOffset(arrayOffset, 8);
bBit = kp.GetBit(byteOffset, bitOffset);
kpCn[0].SetBit(byteOffset, bitOffset, bBit);
// Set bit in KpDn
bBit = kp.GetBit(byteOffset + 4, bitOffset);
kpDn[0].SetBit(byteOffset, bitOffset, bBit);
}
for (arrayOffset = 1; arrayOffset < 17; arrayOffset++)
{
// Shift left wrapped
kpCn[arrayOffset].ShiftLeftWrapped(kpCn[arrayOffset - 1], DESTables.Shifts[arrayOffset - 1]);
kpDn[arrayOffset].ShiftLeftWrapped(kpDn[arrayOffset - 1], DESTables.Shifts[arrayOffset - 1]);
}
// Create 17 keys Kn
for (arrayOffset = 0; arrayOffset < 17; arrayOffset++)
{
// Loop through the bits
int tableOffset;
for (tableOffset = 0; tableOffset < 48; tableOffset++)
{
// Get address if bit
permOffset = DESTables.PC2[tableOffset];
permOffset--;
// Convert to byte and bit offsets
byteOffset = BitAddressToByteOffset(permOffset, 7);
bitOffset = BitAddressToBitOffset(permOffset, 7);
// Get bit
if (byteOffset < 4)
bBit = kpCn[arrayOffset].GetBit(byteOffset, bitOffset);
else
bBit = kpDn[arrayOffset].GetBit(byteOffset - 4, bitOffset);
// Set bit
byteOffset = BitAddressToByteOffset(tableOffset, 6);
bitOffset = BitAddressToBitOffset(tableOffset, 6);
ftmp.GetAt(arrayOffset).SetBit(byteOffset, bitOffset, bBit);
}
}
return ftmp;
}