crypto-js/rc4.js

;(function (root, factory, undef) {
	if (typeof exports === "object") {
		// CommonJS
		module.exports = exports = factory(require("./core"), require("./enc-base64"), require("./md5"), require("./evpkdf"), require("./cipher-core"));
	}
	else if (typeof define === "function" && define.amd) {
		// AMD
		define(["./core", "./enc-base64", "./md5", "./evpkdf", "./cipher-core"], factory);
	}
	else {
		// Global (browser)
		factory(root.CryptoJS);
	}
}(this, function (CryptoJS) {

	(function () {
	    // Shortcuts
	    var C = CryptoJS;
	    var C_lib = C.lib;
	    var StreamCipher = C_lib.StreamCipher;
	    var C_algo = C.algo;

	    /**
	     * RC4 stream cipher algorithm.
	     */
	    var RC4 = C_algo.RC4 = StreamCipher.extend({
	        _doReset: function () {
	            // Shortcuts
	            var key = this._key;
	            var keyWords = key.words;
	            var keySigBytes = key.sigBytes;

	            // Init sbox
	            var S = this._S = [];
	            for (var i = 0; i < 256; i++) {
	                S[i] = i;
	            }

	            // Key setup
	            for (var i = 0, j = 0; i < 256; i++) {
	                var keyByteIndex = i % keySigBytes;
	                var keyByte = (keyWords[keyByteIndex >>> 2] >>> (24 - (keyByteIndex % 4) * 8)) & 0xff;

	                j = (j + S[i] + keyByte) % 256;

	                // Swap
	                var t = S[i];
	                S[i] = S[j];
	                S[j] = t;
	            }

	            // Counters
	            this._i = this._j = 0;
	        },

	        _doProcessBlock: function (M, offset) {
	            M[offset] ^= generateKeystreamWord.call(this);
	        },

	        keySize: 256/32,

	        ivSize: 0
	    });

	    function generateKeystreamWord() {
	        // Shortcuts
	        var S = this._S;
	        var i = this._i;
	        var j = this._j;

	        // Generate keystream word
	        var keystreamWord = 0;
	        for (var n = 0; n < 4; n++) {
	            i = (i + 1) % 256;
	            j = (j + S[i]) % 256;

	            // Swap
	            var t = S[i];
	            S[i] = S[j];
	            S[j] = t;

	            keystreamWord |= S[(S[i] + S[j]) % 256] << (24 - n * 8);
	        }

	        // Update counters
	        this._i = i;
	        this._j = j;

	        return keystreamWord;
	    }

	    /**
	     * Shortcut functions to the cipher's object interface.
	     *
	     * @example
	     *
	     *     var ciphertext = CryptoJS.RC4.encrypt(message, key, cfg);
	     *     var plaintext  = CryptoJS.RC4.decrypt(ciphertext, key, cfg);
	     */
	    C.RC4 = StreamCipher._createHelper(RC4);

	    /**
	     * Modified RC4 stream cipher algorithm.
	     */
	    var RC4Drop = C_algo.RC4Drop = RC4.extend({
	        /**
	         * Configuration options.
	         *
	         * @property {number} drop The number of keystream words to drop. Default 192
	         */
	        cfg: RC4.cfg.extend({
	            drop: 192
	        }),

	        _doReset: function () {
	            RC4._doReset.call(this);

	            // Drop
	            for (var i = this.cfg.drop; i > 0; i--) {
	                generateKeystreamWord.call(this);
	            }
	        }
	    });

	    /**
	     * Shortcut functions to the cipher's object interface.
	     *
	     * @example
	     *
	     *     var ciphertext = CryptoJS.RC4Drop.encrypt(message, key, cfg);
	     *     var plaintext  = CryptoJS.RC4Drop.decrypt(ciphertext, key, cfg);
	     */
	    C.RC4Drop = StreamCipher._createHelper(RC4Drop);
	}());


	return CryptoJS.RC4;

}));