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Viewing changes to lib/cryptojs/components/mode-cfb.js

  • Committer: kapil.foss at gmail
  • Date: 2012-07-13 18:45:59 UTC
  • Revision ID: kapil.foss@gmail.com-20120713184559-2xl7be17egsrz0c9
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lib/cryptojs/components/mode-cfb.js
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/*
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CryptoJS v3.0.2
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code.google.com/p/crypto-js
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(c) 2009-2012 by Jeff Mott. All rights reserved.
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code.google.com/p/crypto-js/wiki/License
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*/
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/**
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 * Cipher Feedback block mode.
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 */
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CryptoJS.mode.CFB = (function () {
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    var CFB = CryptoJS.lib.BlockCipherMode.extend();
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    CFB.Encryptor = CFB.extend({
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        processBlock: function (words, offset) {
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            // Shortcuts
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            var cipher = this._cipher;
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            var blockSize = cipher.blockSize;
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            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
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            // Remember this block to use with next block
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            this._prevBlock = words.slice(offset, offset + blockSize);
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        }
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    });
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    CFB.Decryptor = CFB.extend({
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        processBlock: function (words, offset) {
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            // Shortcuts
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            var cipher = this._cipher;
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            var blockSize = cipher.blockSize;
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            // Remember this block to use with next block
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            var thisBlock = words.slice(offset, offset + blockSize);
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            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);
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            // This block becomes the previous block
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            this._prevBlock = thisBlock;
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        }
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    });
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    function generateKeystreamAndEncrypt(words, offset, blockSize, cipher) {
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        // Shortcut
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        var iv = this._iv;
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        // Generate keystream
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        if (iv) {
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            var keystream = iv.slice(0);
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            // Remove IV for subsequent blocks
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            this._iv = undefined;
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        } else {
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            var keystream = this._prevBlock;
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        }
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        cipher.encryptBlock(keystream, 0);
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        // Encrypt
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        for (var i = 0; i < blockSize; i++) {
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            words[offset + i] ^= keystream[i];
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        }
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    }
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    return CFB;
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}());