Как подписать запрос?

function calcSignature(query) {
        var i, keys = [];
        for (i in query) {
            keys.push(i.toString());
        }
        keys.sort();
        var sign = "";
        for (i = 0; i < keys.length; i++) {
            var key = keys[i];
            if (("sig" != key) && ("access_token" != key)) {
                sign += keys[i] + '=' + query[keys[i]];
            }
        }
        sign += SESSION_SECRET_KEY;
        sign = encodeUtf8(sign);
        return md5(sign);
    }
        var params = {};
        params['name'] = NAME;
        params['price'] = PRICE;
        params['code'] = CODE;
        params["application_key"] = APPKEY;
        if (SESSION_KEY) {
            params["session_key"] = SESSION_KEY;
        } else {
            params["access_token"] = ACCESS_TOKEN;
        }
        params['sig'] = calcSignature(params, SESSION_SECRET_KEY);

        var query = 'https://m.ok.ru/api/show_payment?';
        for (var key in params) {
            if (params.hasOwnProperty(key)) {
                query += key + "=" + encodeURIComponent(params[key]) + "&";
            }
        }

        window.open(query);