MD5 简介 以及 C# 和 js 实现【加密知多少系列】

〇、简介

MD5 是哈希算法（散列算法）的一种应用。Hash 算法虽然被称为算法，但实际上它更像是一种思想。Hash 算法没有一个固定的公式，只要符合散列思想的算法都可以被称为是 Hash 算法。

算法目的就是，把任意长度的输入（又叫做预映射 pre-image），通过散列算法变换成固定长度的输出，该输出就是散列值。

注意，不同的输入可能会散列成相同的输出，所以不能从散列值来确定唯一的输入值。

散列函数简单的说就是：一种将任意长度的消息压缩到某一固定长度的消息摘要的函数。

Hash 算法是一个广义的算法，也可以认为是一种思想，使用 Hash 算法可以提高存储空间的利用率，可以提高数据的查询效率，因为很难找到其逆向规律，也可以做数字签名来保障数据传递的安全性。所以Hash算法被广泛地应用在互联网应用中。

散列值不同 => 原始值不同

  如果两个散列值是不相同的（根据同一函数），那么这两个散列值的原始输入也是不相同的。这个特性是散列函数具有确定性的结果。

散列值相同 ≠> 原始值相同

  散列函数的输入和输出不是一一对应的，如果两个散列值相同，两个输入值很可能是相同的，但不绝对肯定二者一定相等（可能出现哈希碰撞）。

关于“撞库”（Credential Stuffing Attack）

  其在网络安全中是一个古老的概念，按中文的字面意思解读，就是“碰撞数据库”的意思。“碰撞”意味着碰运气，即不一定能成功；而“数据库”中往往存储着大量敏感数据，比如我们登录一个网站所需要的用户名、密码，再比如手机号、身份证号等个人隐私信息。“撞库”在英文中的表述为 Credential Stuffing（密码嗅探），也非常直白的说明了撞库的主要场景：试图获取正确的账号/密码组合，大白话就是“盗号”。

二、C# 代码实现

根据传入参数，返回分大小写的 16 位或 32 位密文，并且可自定义编码规则。

// 测试 string jiamihou16 = SecurityMD5.MD5Encrypt("TestString", 16, false); // 8828701f97fa4511 string jiamihou32 = SecurityMD5.MD5Encrypt("TestString", 32);// 5B56F40F8828701F97FA4511DDCD25FB /// <summary> /// MD5 加密方法 /// </summary> /// <param name="md5instr">待加密字符串</param> /// <param name="digit">位数：16/32/64</param> /// <param name="isupper">输出大小写：true 大写；false 小写(返回为 64 位时不区分大小写)</param> /// <param name="encoding">字符编码规则，为空默认：UTF8</param> /// <returns></returns> public static string MD5Encrypt(string md5instr, int digit, bool isupper = true, Encoding encoding = null) {     string md5outstr = string.Empty;     if (encoding == null)         encoding = Encoding.UTF8;     switch (digit)     {         case 16:             // SecurityMD5.MD5Encrypt(md5instr, 16, true); // 16位大写             // SecurityMD5.MD5Encrypt(md5instr, 16, false); // 16位小写             var md5provider = new MD5CryptoServiceProvider();             var hashinstr16 = md5provider.ComputeHash(encoding.GetBytes(md5instr));             md5outstr = BitConverter.ToString(hashinstr16, 4, 8);             md5outstr = md5outstr.Replace("-", "");             if (!isupper)                 md5outstr = md5outstr.ToLower();             return md5outstr;         case 32:             // SecurityMD5.MD5Encrypt(md5instr, 32, true); // 32位大写             // SecurityMD5.MD5Encrypt(md5instr, 32, false); // 32位小写             MD5 md532 = MD5.Create();             byte[] hashinstr32 = md532.ComputeHash(encoding.GetBytes(md5instr));             string upperorlowerflag = isupper ? "X2" : "x2";             for (int i = 0; i < hashinstr32.Length; i++)             {                 md5outstr = md5outstr + hashinstr32[i].ToString(upperorlowerflag);             }             return md5outstr;         case 64:             // SecurityMD5.MD5Encrypt(md5instr, 64); // 64位加密，加密后为24位的值，例如：9GnLVZEzFmZLMj963TqUEQ==             MD5 md564 = MD5.Create();             byte[] hashinstr64 = md564.ComputeHash(encoding.GetBytes(md5instr));             return Convert.ToBase64String(hashinstr64);         default:             return "";     } }

三、js 代码实现

1/2 通过 crypto-js.js 实现

此方法调用比较简单，但是只能获取 32 位的密文。

// 先引入 js 文件 <script src="http://cdn.bootcdn.net/ajax/libs/crypto-js/4.0.0/crypto-js.js"></script> // npm（Node.js package manager）方式引入 > npm install crypto-js  // 直接调用即可 var jiemihou = CryptoJS.MD5("TestString"); // 57fe567eaa866373f851a526f07d9e26 var jiemihoudx = CryptoJS.MD5("TestString").toString().toUpperCase(); // 5B56F40F8828701F97FA4511DDCD25FB

2/2 通过 js 方法实现

根据传入参数，返回分大小写的 16 位或 32 位密文。

// 测试     md5_function("TestString",16,false)     >'8828701f97fa4511'     md5_function("TestString",32,true)     >'5B56F40F8828701F97FA4511DDCD25FB'  // MD5 加密（入参分别是：待加密内容、返回位数、是否为大写） function md5_function(md5instr, digit, isupper){     function md5_RotateLeft(lValue, iShiftBits) {         return (lValue << iShiftBits) | (lValue >>> (32 - iShiftBits));     }     function md5_AddUnsigned(lX, lY) {         var lX4, lY4, lX8, lY8, lResult;         lX8 = (lX & 0x80000000);         lY8 = (lY & 0x80000000);         lX4 = (lX & 0x40000000);         lY4 = (lY & 0x40000000);         lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);         if (lX4 & lY4) {             return (lResult ^ 0x80000000 ^ lX8 ^ lY8);         }         if (lX4 | lY4) {             if (lResult & 0x40000000) {                 return (lResult ^ 0xC0000000 ^ lX8 ^ lY8);             } else {                 return (lResult ^ 0x40000000 ^ lX8 ^ lY8);             }         } else {             return (lResult ^ lX8 ^ lY8);         }     }     function md5_F(x, y, z) {         return (x & y) | ((~x) & z);     }     function md5_G(x, y, z) {         return (x & z) | (y & (~z));     }     function md5_H(x, y, z) {         return (x ^ y ^ z);     }     function md5_I(x, y, z) {         return (y ^ (x | (~z)));     }     function md5_FF(a, b, c, d, x, s, ac) {         a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_F(b, c, d), x), ac));         return md5_AddUnsigned(md5_RotateLeft(a, s), b);     };     function md5_GG(a, b, c, d, x, s, ac) {         a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_G(b, c, d), x), ac));         return md5_AddUnsigned(md5_RotateLeft(a, s), b);     };     function md5_HH(a, b, c, d, x, s, ac) {         a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_H(b, c, d), x), ac));         return md5_AddUnsigned(md5_RotateLeft(a, s), b);     };     function md5_II(a, b, c, d, x, s, ac) {         a = md5_AddUnsigned(a, md5_AddUnsigned(md5_AddUnsigned(md5_I(b, c, d), x), ac));         return md5_AddUnsigned(md5_RotateLeft(a, s), b);     };     function md5_ConvertToWordArray(md5instr) {         var lWordCount;         var lMessageLength = md5instr.length;         var lNumberOfWords_temp1 = lMessageLength + 8;         var lNumberOfWords_temp2 = (lNumberOfWords_temp1 - (lNumberOfWords_temp1 % 64)) / 64;         var lNumberOfWords = (lNumberOfWords_temp2 + 1) * 16;         var lWordArray = Array(lNumberOfWords - 1);         var lBytePosition = 0;         var lByteCount = 0;         while (lByteCount < lMessageLength) {             lWordCount = (lByteCount - (lByteCount % 4)) / 4;             lBytePosition = (lByteCount % 4) * 8;             lWordArray[lWordCount] = (lWordArray[lWordCount] | (md5instr.charCodeAt(lByteCount) << lBytePosition));             lByteCount++;         }         lWordCount = (lByteCount - (lByteCount % 4)) / 4;         lBytePosition = (lByteCount % 4) * 8;         lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80 << lBytePosition);         lWordArray[lNumberOfWords - 2] = lMessageLength << 3;         lWordArray[lNumberOfWords - 1] = lMessageLength >>> 29;         return lWordArray;     };     function md5_WordToHex(lValue) {         var WordToHexValue = "", WordToHexValue_temp = "", lByte, lCount;         for (lCount = 0; lCount <= 3; lCount++) {             lByte = (lValue >>> (lCount * 8)) & 255;             WordToHexValue_temp = "0" + lByte.toString(16);             WordToHexValue = WordToHexValue + WordToHexValue_temp.substr(WordToHexValue_temp.length - 2, 2);         }         return WordToHexValue;     };     function md5_Utf8Encode(md5instr) {         md5instr = md5instr?.replace(/rn/g, "n");         var utftext = "";         for (var n = 0; n < md5instr.length; n++) {             var c = md5instr.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;     };     var x = Array();     var k, AA, BB, CC, DD, a, b, c, d;     var S11 = 7, S12 = 12, S13 = 17, S14 = 22;     var S21 = 5, S22 = 9, S23 = 14, S24 = 20;     var S31 = 4, S32 = 11, S33 = 16, S34 = 23;     var S41 = 6, S42 = 10, S43 = 15, S44 = 21;     md5instr = md5_Utf8Encode(md5instr);     x = md5_ConvertToWordArray(md5instr);     a = 0x67452301; b = 0xEFCDAB89; c = 0x98BADCFE; d = 0x10325476;     for (k = 0; k < x.length; k += 16) {         AA = a; BB = b; CC = c; DD = d;         a = md5_FF(a, b, c, d, x[k + 0], S11, 0xD76AA478);         d = md5_FF(d, a, b, c, x[k + 1], S12, 0xE8C7B756);         c = md5_FF(c, d, a, b, x[k + 2], S13, 0x242070DB);         b = md5_FF(b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);         a = md5_FF(a, b, c, d, x[k + 4], S11, 0xF57C0FAF);         d = md5_FF(d, a, b, c, x[k + 5], S12, 0x4787C62A);         c = md5_FF(c, d, a, b, x[k + 6], S13, 0xA8304613);         b = md5_FF(b, c, d, a, x[k + 7], S14, 0xFD469501);         a = md5_FF(a, b, c, d, x[k + 8], S11, 0x698098D8);         d = md5_FF(d, a, b, c, x[k + 9], S12, 0x8B44F7AF);         c = md5_FF(c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);         b = md5_FF(b, c, d, a, x[k + 11], S14, 0x895CD7BE);         a = md5_FF(a, b, c, d, x[k + 12], S11, 0x6B901122);         d = md5_FF(d, a, b, c, x[k + 13], S12, 0xFD987193);         c = md5_FF(c, d, a, b, x[k + 14], S13, 0xA679438E);         b = md5_FF(b, c, d, a, x[k + 15], S14, 0x49B40821);         a = md5_GG(a, b, c, d, x[k + 1], S21, 0xF61E2562);         d = md5_GG(d, a, b, c, x[k + 6], S22, 0xC040B340);         c = md5_GG(c, d, a, b, x[k + 11], S23, 0x265E5A51);         b = md5_GG(b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);         a = md5_GG(a, b, c, d, x[k + 5], S21, 0xD62F105D);         d = md5_GG(d, a, b, c, x[k + 10], S22, 0x2441453);         c = md5_GG(c, d, a, b, x[k + 15], S23, 0xD8A1E681);         b = md5_GG(b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);         a = md5_GG(a, b, c, d, x[k + 9], S21, 0x21E1CDE6);         d = md5_GG(d, a, b, c, x[k + 14], S22, 0xC33707D6);         c = md5_GG(c, d, a, b, x[k + 3], S23, 0xF4D50D87);         b = md5_GG(b, c, d, a, x[k + 8], S24, 0x455A14ED);         a = md5_GG(a, b, c, d, x[k + 13], S21, 0xA9E3E905);         d = md5_GG(d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);         c = md5_GG(c, d, a, b, x[k + 7], S23, 0x676F02D9);         b = md5_GG(b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);         a = md5_HH(a, b, c, d, x[k + 5], S31, 0xFFFA3942);         d = md5_HH(d, a, b, c, x[k + 8], S32, 0x8771F681);         c = md5_HH(c, d, a, b, x[k + 11], S33, 0x6D9D6122);         b = md5_HH(b, c, d, a, x[k + 14], S34, 0xFDE5380C);         a = md5_HH(a, b, c, d, x[k + 1], S31, 0xA4BEEA44);         d = md5_HH(d, a, b, c, x[k + 4], S32, 0x4BDECFA9);         c = md5_HH(c, d, a, b, x[k + 7], S33, 0xF6BB4B60);         b = md5_HH(b, c, d, a, x[k + 10], S34, 0xBEBFBC70);         a = md5_HH(a, b, c, d, x[k + 13], S31, 0x289B7EC6);         d = md5_HH(d, a, b, c, x[k + 0], S32, 0xEAA127FA);         c = md5_HH(c, d, a, b, x[k + 3], S33, 0xD4EF3085);         b = md5_HH(b, c, d, a, x[k + 6], S34, 0x4881D05);         a = md5_HH(a, b, c, d, x[k + 9], S31, 0xD9D4D039);         d = md5_HH(d, a, b, c, x[k + 12], S32, 0xE6DB99E5);         c = md5_HH(c, d, a, b, x[k + 15], S33, 0x1FA27CF8);         b = md5_HH(b, c, d, a, x[k + 2], S34, 0xC4AC5665);         a = md5_II(a, b, c, d, x[k + 0], S41, 0xF4292244);         d = md5_II(d, a, b, c, x[k + 7], S42, 0x432AFF97);         c = md5_II(c, d, a, b, x[k + 14], S43, 0xAB9423A7);         b = md5_II(b, c, d, a, x[k + 5], S44, 0xFC93A039);         a = md5_II(a, b, c, d, x[k + 12], S41, 0x655B59C3);         d = md5_II(d, a, b, c, x[k + 3], S42, 0x8F0CCC92);         c = md5_II(c, d, a, b, x[k + 10], S43, 0xFFEFF47D);         b = md5_II(b, c, d, a, x[k + 1], S44, 0x85845DD1);         a = md5_II(a, b, c, d, x[k + 8], S41, 0x6FA87E4F);         d = md5_II(d, a, b, c, x[k + 15], S42, 0xFE2CE6E0);         c = md5_II(c, d, a, b, x[k + 6], S43, 0xA3014314);         b = md5_II(b, c, d, a, x[k + 13], S44, 0x4E0811A1);         a = md5_II(a, b, c, d, x[k + 4], S41, 0xF7537E82);         d = md5_II(d, a, b, c, x[k + 11], S42, 0xBD3AF235);         c = md5_II(c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);         b = md5_II(b, c, d, a, x[k + 9], S44, 0xEB86D391);         a = md5_AddUnsigned(a, AA);         b = md5_AddUnsigned(b, BB);         c = md5_AddUnsigned(c, CC);         d = md5_AddUnsigned(d, DD);     }     if(digit == 16){         if(isupper)             return (md5_WordToHex(b) + md5_WordToHex(c)).toUpperCase();         else             return (md5_WordToHex(b) + md5_WordToHex(c)).toLowerCase();     }     else if (digit == 32){         if(isupper)             return (md5_WordToHex(a) + md5_WordToHex(b) + md5_WordToHex(c) + md5_WordToHex(d)).toUpperCase();         else             return (md5_WordToHex(a) + md5_WordToHex(b) + md5_WordToHex(c) + md5_WordToHex(d)).toLowerCase();     }     return ""; }