(function () {
    // Shortcuts
    var C = CryptoJS;
    var C_lib = C.lib;
    var Base = C_lib.Base;
    var WordArray = C_lib.WordArray;
    var C_algo = C.algo;
    var MD5 = C_algo.MD5;

    /**
     * This key derivation function is meant to conform with EVP_BytesToKey.
     * www.openssl.org/docs/crypto/EVP_BytesToKey.html
     */
    var EvpKDF = C_algo.EvpKDF = Base.extend({
        /**
         * Configuration options.
         *
         * @property {number} keySize The key size in words to generate. Default: 4 (128 bits)
         * @property {Hasher} hasher The hash algorithm to use. Default: MD5
         * @property {number} iterations The number of iterations to perform. Default: 1
         */
        cfg: Base.extend({
            keySize: 128/32,
            hasher: MD5,
            iterations: 1
        }),

        /**
         * Initializes a newly created key derivation function.
         *
         * @param {Object} cfg (Optional) The configuration options to use for the derivation.
         *
         * @example
         *
         *     var kdf = CryptoJS.algo.EvpKDF.create();
         *     var kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8 });
         *     var kdf = CryptoJS.algo.EvpKDF.create({ keySize: 8, iterations: 1000 });
         */
        init: function (cfg) {
            this.cfg = this.cfg.extend(cfg);
        },

        /**
         * Derives a key from a password.
         *
         * @param {WordArray|string} password The password.
         * @param {WordArray|string} salt A salt.
         *
         * @return {WordArray} The derived key.
         *
         * @example
         *
         *     var key = kdf.compute(password, salt);
         */
        compute: function (password, salt) {
            var block;

            // Shortcut
            var cfg = this.cfg;

            // Init hasher
            var hasher = cfg.hasher.create();

            // Initial values
            var derivedKey = WordArray.create();

            // Shortcuts
            var derivedKeyWords = derivedKey.words;
            var keySize = cfg.keySize;
            var iterations = cfg.iterations;

            // Generate key
            while (derivedKeyWords.length < keySize) {
                if (block) {
                    hasher.update(block);
                }
                block = hasher.update(password).finalize(salt);
                hasher.reset();

                // Iterations
                for (var i = 1; i < iterations; i++) {
                    block = hasher.finalize(block);
                    hasher.reset();
                }

                derivedKey.concat(block);
            }
            derivedKey.sigBytes = keySize * 4;

            return derivedKey;
        }
    });

    /**
     * Derives a key from a password.
     *
     * @param {WordArray|string} password The password.
     * @param {WordArray|string} salt A salt.
     * @param {Object} cfg (Optional) The configuration options to use for this computation.
     *
     * @return {WordArray} The derived key.
     *
     * @static
     *
     * @example
     *
     *     var key = CryptoJS.EvpKDF(password, salt);
     *     var key = CryptoJS.EvpKDF(password, salt, { keySize: 8 });
     *     var key = CryptoJS.EvpKDF(password, salt, { keySize: 8, iterations: 1000 });
     */
    C.EvpKDF = function (password, salt, cfg) {
        return EvpKDF.create(cfg).compute(password, salt);
    };
}());