crypto-js/mode-cfb.js

;(function (root, factory, undef) {
	if (typeof exports === "object") {
		// CommonJS
		module.exports = exports = factory(require("./core"), require("./cipher-core"));
	}
	else if (typeof define === "function" && define.amd) {
		// AMD
		define(["./core", "./cipher-core"], factory);
	}
	else {
		// Global (browser)
		factory(root.CryptoJS);
	}
}(this, function (CryptoJS) {

	/**
	 * Cipher Feedback block mode.
	 */
	CryptoJS.mode.CFB = (function () {
	    var CFB = CryptoJS.lib.BlockCipherMode.extend();

	    CFB.Encryptor = CFB.extend({
	        processBlock: function (words, offset) {
	            // Shortcuts
	            var cipher = this._cipher;
	            var blockSize = cipher.blockSize;

	            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);

	            // Remember this block to use with next block
	            this._prevBlock = words.slice(offset, offset + blockSize);
	        }
	    });

	    CFB.Decryptor = CFB.extend({
	        processBlock: function (words, offset) {
	            // Shortcuts
	            var cipher = this._cipher;
	            var blockSize = cipher.blockSize;

	            // Remember this block to use with next block
	            var thisBlock = words.slice(offset, offset + blockSize);

	            generateKeystreamAndEncrypt.call(this, words, offset, blockSize, cipher);

	            // This block becomes the previous block
	            this._prevBlock = thisBlock;
	        }
	    });

	    function generateKeystreamAndEncrypt(words, offset, blockSize, cipher) {
	        // Shortcut
	        var iv = this._iv;

	        // Generate keystream
	        if (iv) {
	            var keystream = iv.slice(0);

	            // Remove IV for subsequent blocks
	            this._iv = undefined;
	        } else {
	            var keystream = this._prevBlock;
	        }
	        cipher.encryptBlock(keystream, 0);

	        // Encrypt
	        for (var i = 0; i < blockSize; i++) {
	            words[offset + i] ^= keystream[i];
	        }
	    }

	    return CFB;
	}());


	return CryptoJS.mode.CFB;

}));