详解MD5算法的原理以及C#和JS的实现
作者:橙子家
一、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
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(/\r\n/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 ""; }
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