crypto-js/mode-ofb.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) {

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

	    var Encryptor = OFB.Encryptor = OFB.extend({
	        processBlock: function (words, offset) {
	            // Shortcuts
	            var cipher = this._cipher
	            var blockSize = cipher.blockSize;
	            var iv = this._iv;
	            var keystream = this._keystream;

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

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

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

	    OFB.Decryptor = Encryptor;

	    return OFB;
	}());


	return CryptoJS.mode.OFB;

}));