mode-ctr-gladman.js
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/** @preserve
* Counter block mode compatible with Dr Brian Gladman fileenc.c
* derived from CryptoJS.mode.CTR
* Jan Hruby jhruby.web@gmail.com
*/
CryptoJS.mode.CTRGladman = (function () {
var CTRGladman = CryptoJS.lib.BlockCipherMode.extend();
function incWord(word)
{
if (((word >> 24) & 0xff) === 0xff) { //overflow
var b1 = (word >> 16)&0xff;
var b2 = (word >> 8)&0xff;
var b3 = word & 0xff;
if (b1 === 0xff) // overflow b1
{
b1 = 0;
if (b2 === 0xff)
{
b2 = 0;
if (b3 === 0xff)
{
b3 = 0;
}
else
{
++b3;
}
}
else
{
++b2;
}
}
else
{
++b1;
}
word = 0;
word += (b1 << 16);
word += (b2 << 8);
word += b3;
}
else
{
word += (0x01 << 24);
}
return word;
}
function incCounter(counter)
{
if ((counter[0] = incWord(counter[0])) === 0)
{
// encr_data in fileenc.c from Dr Brian Gladman's counts only with DWORD j < 8
counter[1] = incWord(counter[1]);
}
return counter;
}
var Encryptor = CTRGladman.Encryptor = CTRGladman.extend({
processBlock: function (words, offset) {
// Shortcuts
var cipher = this._cipher
var blockSize = cipher.blockSize;
var iv = this._iv;
var counter = this._counter;
// Generate keystream
if (iv) {
counter = this._counter = iv.slice(0);
// Remove IV for subsequent blocks
this._iv = undefined;
}
incCounter(counter);
var keystream = counter.slice(0);
cipher.encryptBlock(keystream, 0);
// Encrypt
for (var i = 0; i < blockSize; i++) {
words[offset + i] ^= keystream[i];
}
}
});
CTRGladman.Decryptor = Encryptor;
return CTRGladman;
}());