public static String Decode(String content, Boolean force)
{
StringBuilder builder = new StringBuilder();
content = force ? Utf8.Decode(content) : content;
int i = 0;
List <String> strings = new List <String>(content.Length);
while (i < content.Length)
{
uint a = (uint)Base64.Code.IndexOf(content[i]);
uint b = (uint)Base64.Code.IndexOf(content[i + 1]);
uint c = (uint)Base64.Code.IndexOf(content[i + 2]);
uint d = (uint)Base64.Code.IndexOf(content[i + 3]);
uint e = ((a << 18) | (b << 12) | (c << 6) | d);
uint f = ((e >> 16) & 0xFF);
uint g = ((e >> 8) & 0xFF);
uint h = (e & 0xFF);
strings.Add(new String(new Char[] { (Char)f, (Char)g, (Char)h }));
if (d == 64)
{
strings[i / 4] = new String(new Char[] { (Char)f, (Char)g });
}
if (c == 64)
{
strings[i / 4] = new String(new Char[] { (Char)f });
}
i += 4;
}
foreach (var str in strings)
{
builder.Append(str);
}
return((force) ? Utf8.Decode(builder.ToString()) : builder.ToString());
}
public static String Decrypt(String cipherText, String password, KeyType keyType)
{
int blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
int bits = (int)keyType;
cipherText = Base64.Decode(cipherText, false);
password = Utf8.Encode(password);
// use AES to encrypt password (mirroring encrypt routine)
int bytes = bits / 8; // no bytes in key
int[] pwBytes = new int[bytes];
for (int i = 0; i < bytes; i++)
{
pwBytes[i] = password[i];
}
int[] temp = Cipher(pwBytes, KeyExpansion(pwBytes));
int[] key = new int[temp.Length + bytes - 16];
// expand key to 16/24/32 bytes long
for (int i = 0; i < temp.Length; i++)
{
key[i] = temp[i];
}
for (int i = temp.Length; i < (temp.Length + bytes - 16); i++)
{
key[i] = temp[i - temp.Length];
}
// recover nonce from 1st 8 bytes of ciphertext
int[] counterBlock = new int[16];
String ctrTxt = cipherText.Substring(0, 8);
for (int i = 0; i < 8; i++)
{
counterBlock[i] = ctrTxt[i];
}
// generate key schedule
int[,] keySchedule = KeyExpansion(key);
// separate ciphertext into blocks (skipping past initial 8 bytes)
int blocks = (int)Math.Ceiling((double)(cipherText.Length - 8) / (double)blockSize);
String[] ct = new String[blocks];
for (int i = 0; i < blocks; i++)
{
//ct[i] = cipherText.Substring(8 + i * blockSize, blockSize);
ct[i] = cipherText.Substring(8 + i * blockSize, Math.Min(cipherText.Length - 8 - i * blockSize, blockSize));
}
String[] ciphertextArr = ct; // ciphertext is now array of block-length strings
// plaintext will get generated block-by-block into array of block-length strings
String[] plaintxt = new String[ciphertextArr.Length];
for (int i = 0; i < blocks; i++)
{
// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
for (int j = 0; j < 4; j++)
{
counterBlock[15 - j] = (i >> (j * 8)) & 0xFF;
}
for (int j = 0; j < 4; j++)
{
//counterBlock[15 - j - 4] = (((b + 1) / 0x100000000 - 1) >>> c * 8) & 0xff;
counterBlock[15 - j - 4] = 0;
}
int[] cipherCntr = Cipher(counterBlock, keySchedule); // encrypt counter block
Char[] plaintxtByte = new Char[ciphertextArr[i].Length];
for (int j = 0; j < ciphertextArr[i].Length; j++)
{
// -- xor plaintxt with ciphered counter byte-by-byte --
plaintxtByte[j] = (Char)(cipherCntr[j] ^ ciphertextArr[i][j]);
//plaintxtByte[j] = String.fromCharCode(plaintxtByte[j]);
}
//plaintxt[i] = plaintxtByte.join('');
plaintxt[i] = new String(plaintxtByte);
}
// join array of blocks into single plaintext string
//var plaintext : String = plaintxt.join('');
//plaintext = Utf8.decode(plaintext); // decode from UTF8 back to Unicode multi-byte chars
StringBuilder builder = new StringBuilder();
foreach (var str in plaintxt)
{
builder.Append(str);
}
return(Utf8.Decode(builder.ToString()));
}
