JavaScript Base64加解密

Base64加密算法是网络上最常见的用于传输8Bit字节代码的编码方式之一，大家可以查看RFC2045～RFC2049，上面有MIME的详细规范。Base64编码可用于在HTTP环境下传递较长的标识信息。例如，在Java Persistence系统Hibernate中，就采用了Base64来将一个较长的唯一标识符（一般为128-bit的UUID）编码为一个字符串，用作HTTP表单和HTTP GET URL中的参数。在其他应用程序中，也常常需要把二进制数据编码为适合放在URL（包括隐藏表单域）中的形式。此时，采用Base64编码具有不可读性，即所编码的数据不会被人用肉眼所直接看到。

下面是Base64加密、解密算法的简单实现(不支持中文)：

function base64Encrypt(baseString) {

    var base64Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    var length = baseString.length;

    var loopNo = parseInt(length / 3);

    var charOne, charTwo, charThree;

    var out = "";

    for (var i = 0, j = 0; j < loopNo; j++) {

        charOne = baseString.charCodeAt(i++);

        charTwo = baseString.charCodeAt(i++);

        charThree = baseString.charCodeAt(i++);

        out += base64Chars.charAt(charOne >> 2);

        out += base64Chars.charAt(((charOne & 0x3) << 4) | ((charTwo & 0xF0) >> 4));

        out += base64Chars.charAt(((charTwo & 0xF) << 2) | ((charThree & 0xC0) >> 6));

        out += base64Chars.charAt(charThree & 0x3F);

    }

    if (i === length) {

        return out;

    }

    charOne = baseString.charCodeAt(i++) & 0xff;

    out += base64Chars.charAt(charOne >> 2);

    if (i === length) {

        out += base64Chars.charAt((charOne & 0x3) << 4);

        out += "==";

    } else {

        charTwo = baseString.charCodeAt(i++);

        out += base64Chars.charAt(((charOne & 0x3) << 4) | ((charTwo & 0xF0) >> 4));

        out += base64Chars.charAt((charTwo & 0xF) << 2);

        out += "=";

    }

    return out;

}

function base64Encode(baseSting) {

    var base64Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    var length = baseSting.length;

    var chara1, chara2, chara3;

    var out = "", i = 0;

    while (i < length) {

        chara1 = baseSting.charCodeAt(i++) & 0xff;

        out += base64Chars.charAt(chara1 >> 2);

        if (i == length) {

            out += base64Chars.charAt((chara1 & 0x3) << 4);

            out += "==";

            break;

        }

        chara2 = baseSting.charCodeAt(i++);

        if (i == length) {

            out += base64Chars.charAt(((chara1 & 0x3) << 4) | ((chara2 & 0xF0) >> 4));

            out += base64Chars.charAt((chara2 & 0xF) << 2);

            out += "=";

            break;

        }

        chara3 = baseSting.charCodeAt(i++);

        out += base64Chars.charAt(((chara1 & 0x3) << 4) | ((chara2 & 0xF0) >> 4));

        out += base64Chars.charAt(((chara2 & 0xF) << 2) | ((chara3 & 0xC0) >> 6));

        out += base64Chars.charAt(chara3 & 0x3F);

    }

    return out;

}

function base64Decode(baseString) {

    var base64Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    var length = baseString.length;

    var charI, charII, charIII, charIV;

    var out = "", i = 0;

    if (0 < length && 0 === length % 4) {

        if (/^[A-Za-z0-9\+/]{2,}={0,2}$/.test(baseString)) {

            while (i < length - 4) {

                charI = base64Chars.indexOf(baseString.charAt(i++));

                charII = base64Chars.indexOf(baseString.charAt(i++));

                charIII = base64Chars.indexOf(baseString.charAt(i++));

                charIV = base64Chars.indexOf(baseString.charAt(i++));

                out += String.fromCharCode((charI << 2) | ((charII & 0x30) >> 4));

                out += String.fromCharCode(((charII & 0xF) << 4) | ((charIII & 0x3C) >> 2));

                out += String.fromCharCode(((charIII & 0x3) << 6) | charIV);

            }

            charI = base64Chars.indexOf(baseString.charAt(i++));

            charII = base64Chars.indexOf(baseString.charAt(i++));

            out += String.fromCharCode((charI << 2) | ((charII & 0x30) >> 4));

            switch (baseString.indexOf("=")) {

                case length - 1:

                    charIII = base64Chars.indexOf(baseString.charAt(i++));

                    out += String.fromCharCode(((charII & 0xF) << 4) | ((charIII & 0x3C) >> 2));

                    break;

                case -1:

                    charIII = base64Chars.indexOf(baseString.charAt(i++));

                    charIV = base64Chars.indexOf(baseString.charAt(i++));

                    out += String.fromCharCode(((charII & 0xF) << 4) | ((charIII & 0x3C) >> 2));

                    out += String.fromCharCode(((charIII & 0x3) << 6) | charIV);

            }

        } else {

            throw new Error(baseString + " does not base64 encoded string.");

        }

    } else {

        throw new Error(baseString + " does not base64 encoded string.");

    }

    return out;

}

巴特西

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