filer/lib/crypto-js/components/mode-ctr.js

45 lines
1.2 KiB
JavaScript

/*
CryptoJS v3.0.2
code.google.com/p/crypto-js
(c) 2009-2012 by Jeff Mott. All rights reserved.
code.google.com/p/crypto-js/wiki/License
*/
/**
* Counter block mode.
*/
CryptoJS.mode.CTR = (function () {
var CTR = CryptoJS.lib.BlockCipherMode.extend();
var Encryptor = CTR.Encryptor = CTR.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;
}
var keystream = counter.slice(0);
cipher.encryptBlock(keystream, 0);
// Increment counter
counter[blockSize - 1] = (counter[blockSize - 1] + 1) | 0
// Encrypt
for (var i = 0; i < blockSize; i++) {
words[offset + i] ^= keystream[i];
}
}
});
CTR.Decryptor = Encryptor;
return CTR;
}());