因项目需求，需要对用户信息进行加密(以登录为例),前台js中对用户名密码进行加密传输。 1.前台JS

    <script type="text/javascript">  
        $(function() {  
            $("#btn").click(function() {  
                var username = encode64($("#username").val());  //对数据加密  
                var password = encode64($("#password").val());  
                $("#username").val(username);  
                $("#password").val(password);  
                document.fm.submit();  //fm为form表单name  
            })  
        })  
          
        // base64加密开始  
        var keyStr = "ABCDEFGHIJKLMNOP" + "QRSTUVWXYZabcdef" + "ghijklmnopqrstuv"  
                + "wxyz0123456789+/" + "=";  
          
        function encode64(input) {  
      
            var output = "";  
            var chr1, chr2, chr3 = "";  
            var enc1, enc2, enc3, enc4 = "";  
            var i = 0;  
            do {  
                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);  
                chr1 = chr2 = chr3 = "";  
                enc1 = enc2 = enc3 = enc4 = "";  
            } while (i < input.length);  
      
            return output;  
        }  
        // base64加密结束  
    </script>  

2、后台java代码

    private static char[] base64EncodeChars = new char[] { 'A', 'B', 'C', 'D',  
            'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q',  
            'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',  
            'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q',  
            'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3',  
            '4', '5', '6', '7', '8', '9', '+', '/', };  
      
    private static byte[] base64DecodeChars = new byte[] { -1, -1, -1, -1, -1,  
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  
            -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59,  
            60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,  
            10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,  
            -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,  
            38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,  
            -1, -1 };  
      
    /** 
     * 解密 
     * @param str 
     * @return 
     */  
    public static byte[] decode(String str) {  
        byte[] data = str.getBytes();  
        int len = data.length;  
        ByteArrayOutputStream buf = new ByteArrayOutputStream(len);  
        int i = 0;  
        int b1, b2, b3, b4;  
      
        while (i < len) {  
            do {  
                b1 = base64DecodeChars[data[i++]];  
            } while (i < len && b1 == -1);  
            if (b1 == -1) {  
                break;  
            }  
      
            do {  
                b2 = base64DecodeChars[data[i++]];  
            } while (i < len && b2 == -1);  
            if (b2 == -1) {  
                break;  
            }  
            buf.write((int) ((b1 << 2) | ((b2 & 0x30) >>> 4)));  
      
            do {  
                b3 = data[i++];  
                if (b3 == 61) {  
                    return buf.toByteArray();  
                }  
                b3 = base64DecodeChars[b3];  
            } while (i < len && b3 == -1);  
            if (b3 == -1) {  
                break;  
            }  
            buf.write((int) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));  
      
            do {  
                b4 = data[i++];  
                if (b4 == 61) {  
                    return buf.toByteArray();  
                }  
                b4 = base64DecodeChars[b4];  
            } while (i < len && b4 == -1);  
            if (b4 == -1) {  
                break;  
            }  
            buf.write((int) (((b3 & 0x03) << 6) | b4));  
        }  
        return buf.toByteArray();  
    }  

System.out.println(new String(decode(username)));  // 使用decode()方法进行解密

Java加密算法还包括如下：

MD5(Message Digest algorithm 5，信息摘要算法)

SHA(Secure Hash Algorithm，安全散列算法)

HMAC(Hash Message Authentication Code，散列消息鉴别码)