function Base64() {

    // private property

    _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    // public method for encoding

    this.encode = function (input) {

        var output = "";

        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;

        var i = 0;

        input = _utf8_encode(input);

        while (i < input.length) {

            chr1 = input.charCodeAt(i++);

            chr2 = input.charCodeAt(i++);

            chr3 = input.charCodeAt(i++);

            enc1 = chr1 >> 2;

            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);

            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);

            enc4 = chr3 & 63;

            if (isNaN(chr2)) {

                enc3 = enc4 = 64;

            } else if (isNaN(chr3)) {

                enc4 = 64;

            }

            output = output +

            _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +

            _keyStr.charAt(enc3) + _keyStr.charAt(enc4);

        }

        return output;

    }

    // public method for decoding

    this.decode = function (input) {

        var output = "";

        var chr1, chr2, chr3;

        var enc1, enc2, enc3, enc4;

        var i = 0;

        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

        while (i < input.length) {

            enc1 = _keyStr.indexOf(input.charAt(i++));

            enc2 = _keyStr.indexOf(input.charAt(i++));

            enc3 = _keyStr.indexOf(input.charAt(i++));

            enc4 = _keyStr.indexOf(input.charAt(i++));

            chr1 = (enc1 << 2) | (enc2 >> 4);

            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);

            chr3 = ((enc3 & 3) << 6) | enc4;

            output = output + String.fromCharCode(chr1);

            if (enc3 != 64) {

                output = output + String.fromCharCode(chr2);

            }

            if (enc4 != 64) {

                output = output + String.fromCharCode(chr3);

            }

        }

        output = _utf8_decode(output);

        return output;

    }

    // private method for UTF-8 encoding

    _utf8_encode = function (string) {

        string = string.replace(/\r\n/g,"\n");

        var utftext = "";

        for (var n = 0; n < string.length; n++) {

            var c = string.charCodeAt(n);

            if (c < 128) {

                utftext += String.fromCharCode(c);

            } else if((c > 127) && (c < 2048)) {

                utftext += String.fromCharCode((c >> 6) | 192);

                utftext += String.fromCharCode((c & 63) | 128);

            } else {

                utftext += String.fromCharCode((c >> 12) | 224);

                utftext += String.fromCharCode(((c >> 6) & 63) | 128);

                utftext += String.fromCharCode((c & 63) | 128);

            }

        }

        return utftext;

    }

    // private method for UTF-8 decoding

    _utf8_decode = function (utftext) {

        var string = "";

        var i = 0;

        var c = c1 = c2 = 0;

        while ( i < utftext.length ) {

            c = utftext.charCodeAt(i);

            if (c < 128) {

                string += String.fromCharCode(c);

                i++;

            } else if((c > 191) && (c < 224)) {

                c2 = utftext.charCodeAt(i+1);

                string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));

                i += 2;

            } else {

                c2 = utftext.charCodeAt(i+1);

                c3 = utftext.charCodeAt(i+2);

                string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));

                i += 3;

            }

        }

        return string;

    }

}