aboutsummaryrefslogtreecommitdiffstats
path: root/library/cryptojs/components/mode-ctr.js
blob: f93e4abfb6e23b55d093cf558caf8d986c117d33 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
/*
CryptoJS v3.1.2
code.google.com/p/crypto-js
(c) 2009-2013 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;
}());