public static string Decrypt(string keyHex, string cipher)
{
var subKeys = SplitKey(keyHex);
var bitBlocks = SplitToBitBlocks(cipher);
var decryptedBits = new List <int[]>();
for (int i = 0; i < bitBlocks.Count; i++)
{
DES.Encrypt(subKeys.Item3, bitBlocks[i]);
int[] decrypted3 = DES.Decrypt(subKeys.Item3, bitBlocks[i]);
int[] decrypted2 = DES.Encrypt(subKeys.Item2, decrypted3);
int[] decrypted1 = DES.Decrypt(subKeys.Item1, decrypted2);
decryptedBits.Add(decrypted1);
}
// Remove padding
int paddingValue = decryptedBits.Last().First();
int lastIndex = decryptedBits.Count - 1;
decryptedBits.RemoveAt(lastIndex--); // Remove last additional block contains only padding value
decryptedBits[lastIndex] = decryptedBits[lastIndex].TrimEnd(paddingValue);
string decryptedHex = HexConverter.BitsToHex(decryptedBits);
return(HexConverter.HexStrToStr(decryptedHex));
}
public static string Decrypt(string keyHex, string cipherHex)
{
int[] cipherBits = GetBitsFromHexStr(cipherHex);
int[] keyBits = GetBitsFromHexStr(keyHex);
int[] decryptedBits = Permute(cipherBits, keyBits, true);
return(HexConverter.BitsToHex(decryptedBits));
}
public static string Encrypt(string keyHex, string strHexToEncrypt)
{
var subKeys = SplitKey(keyHex);
var bitBlocks = SplitToBitBlocksUsingTBC(strHexToEncrypt);
var encryptedBits = new List <int[]>();
for (int i = 0; i < bitBlocks.Count; i++)
{
int[] cipher1 = DES.Encrypt(subKeys.Item1, bitBlocks[i]);
int[] cipher2 = DES.Decrypt(subKeys.Item2, cipher1);
int[] cipher3 = DES.Encrypt(subKeys.Item3, cipher2);
encryptedBits.Add(cipher3);
}
return(HexConverter.BitsToHex(encryptedBits));
}
public string Encrypt(string keyHex, string strHexToEncrypt)
{
// inputBits will store the 64 bits of the input as a an int array of
// size 64. This program uses int arrays to store bits, for the sake
// of simplicity. For efficient programming, use long data type. But
// it increases program complexity which is unnecessary for this
// context.
int[] inputBits = GetBitsFromHexStr(strHexToEncrypt);
int[] keyBits = GetBitsFromHexStr(keyHex);
// permute(int[] inputBits, int[] keyBits, boolean isDecrypt)
// method is used here. This allows encryption and decryption to be
// done in the same method, reducing code.
int[] cipher = Permute(inputBits, keyBits, false);
return(HexConverter.BitsToHex(cipher));
}
