我要评论一、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 "";
}以上就是详解md5算法的原理以及c#和js的实现的详细内容，更多关于md5算法的资料请关注七九推其它相关文章！
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