解析MD5算法

MD5实现128bit的Hash值的密码散列函数

1、MD5的作用：

在传输的时候，进行加密，防止恶意窃取数据。

2、MD5算法的原理：

填充输入信息，使其字节长度对512求余数为448.

信息的长度扩展为N*512+448 bit N为整数。然后将每个512bit的组分为16个32bit子分组，最后经过一系列的算法生成4个32bit共128bit的散列值

3、MD5算法的实现：

 

/* eslint-disable */
var jQuery = require('jquery');
(function($){
  var rotateLeft = function(lValue, iShiftBits) {
    return (lValue << iShiftBits) | (lValue >>> (32 - iShiftBits));
  }
  var addUnsigned = function(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);
    }
  }
  var F = function(x, y, z) {
    return (x & y) | ((~ x) & z);
  }
  var G = function(x, y, z) {
    return (x & z) | (y & (~ z));
  }
  var H = function(x, y, z) {
    return (x ^ y ^ z);
  }
  var I = function(x, y, z) {
    return (y ^ (x | (~ z)));
  }
  var FF = function(a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(F(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };
  var GG = function(a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(G(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };
  var HH = function(a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(H(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };
  var II = function(a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(I(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };
  var convertToWordArray = function(string) {
    var lWordCount;
    var lMessageLength = string.length;
    var lNumberOfWordsTempOne = lMessageLength + 8;
    var lNumberOfWordsTempTwo = (lNumberOfWordsTempOne - (lNumberOfWordsTempOne % 64)) / 64;
    var lNumberOfWords = (lNumberOfWordsTempTwo + 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] | (string.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;
  };
  var wordToHex = function(lValue) {
    var WordToHexValue = "", WordToHexValueTemp = "", lByte, lCount;
    for (lCount = 0; lCount <= 3; lCount++) {
      lByte = (lValue >>> (lCount * 8)) & 255;
      WordToHexValueTemp = "0" + lByte.toString(16);
      WordToHexValue = WordToHexValue + WordToHexValueTemp.substr(WordToHexValueTemp.length - 2, 2);
    }
    return WordToHexValue;
  };
  var uTF8Encode = function(string) {
    string = string.replace(/x0dx0a/g, "x0a");
    var output = "";
    for (var n = 0; n < string.length; n++) {
      var c = string.charCodeAt(n);
      if (c < 128) {
        output += String.fromCharCode(c);
      } else if ((c > 127) && (c < 2048)) {
        output += String.fromCharCode((c >> 6) | 192);
        output += String.fromCharCode((c & 63) | 128);
      } else {
        output += String.fromCharCode((c >> 12) | 224);
        output += String.fromCharCode(((c >> 6) & 63) | 128);
        output += String.fromCharCode((c & 63) | 128);
      }
    }
    return output;
  };
  $.extend({
    md5: function(string) {
      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;
      string = uTF8Encode(string);
      x = convertToWordArray(string);
      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 = FF(a, b, c, d, x[k+0],  S11, 0xD76AA478);
        d = FF(d, a, b, c, x[k+1],  S12, 0xE8C7B756);
        c = FF(c, d, a, b, x[k+2],  S13, 0x242070DB);
        b = FF(b, c, d, a, x[k+3],  S14, 0xC1BDCEEE);
        a = FF(a, b, c, d, x[k+4],  S11, 0xF57C0FAF);
        d = FF(d, a, b, c, x[k+5],  S12, 0x4787C62A);
        c = FF(c, d, a, b, x[k+6],  S13, 0xA8304613);
        b = FF(b, c, d, a, x[k+7],  S14, 0xFD469501);
        a = FF(a, b, c, d, x[k+8],  S11, 0x698098D8);
        d = FF(d, a, b, c, x[k+9],  S12, 0x8B44F7AF);
        c = FF(c, d, a, b, x[k+10], S13, 0xFFFF5BB1);
        b = FF(b, c, d, a, x[k+11], S14, 0x895CD7BE);
        a = FF(a, b, c, d, x[k+12], S11, 0x6B901122);
        d = FF(d, a, b, c, x[k+13], S12, 0xFD987193);
        c = FF(c, d, a, b, x[k+14], S13, 0xA679438E);
        b = FF(b, c, d, a, x[k+15], S14, 0x49B40821);
        a = GG(a, b, c, d, x[k+1],  S21, 0xF61E2562);
        d = GG(d, a, b, c, x[k+6],  S22, 0xC040B340);
        c = GG(c, d, a, b, x[k+11], S23, 0x265E5A51);
        b = GG(b, c, d, a, x[k+0],  S24, 0xE9B6C7AA);
        a = GG(a, b, c, d, x[k+5],  S21, 0xD62F105D);
        d = GG(d, a, b, c, x[k+10], S22, 0x2441453);
        c = GG(c, d, a, b, x[k+15], S23, 0xD8A1E681);
        b = GG(b, c, d, a, x[k+4],  S24, 0xE7D3FBC8);
        a = GG(a, b, c, d, x[k+9],  S21, 0x21E1CDE6);
        d = GG(d, a, b, c, x[k+14], S22, 0xC33707D6);
        c = GG(c, d, a, b, x[k+3],  S23, 0xF4D50D87);
        b = GG(b, c, d, a, x[k+8],  S24, 0x455A14ED);
        a = GG(a, b, c, d, x[k+13], S21, 0xA9E3E905);
        d = GG(d, a, b, c, x[k+2],  S22, 0xFCEFA3F8);
        c = GG(c, d, a, b, x[k+7],  S23, 0x676F02D9);
        b = GG(b, c, d, a, x[k+12], S24, 0x8D2A4C8A);
        a = HH(a, b, c, d, x[k+5],  S31, 0xFFFA3942);
        d = HH(d, a, b, c, x[k+8],  S32, 0x8771F681);
        c = HH(c, d, a, b, x[k+11], S33, 0x6D9D6122);
        b = HH(b, c, d, a, x[k+14], S34, 0xFDE5380C);
        a = HH(a, b, c, d, x[k+1],  S31, 0xA4BEEA44);
        d = HH(d, a, b, c, x[k+4],  S32, 0x4BDECFA9);
        c = HH(c, d, a, b, x[k+7],  S33, 0xF6BB4B60);
        b = HH(b, c, d, a, x[k+10], S34, 0xBEBFBC70);
        a = HH(a, b, c, d, x[k+13], S31, 0x289B7EC6);
        d = HH(d, a, b, c, x[k+0],  S32, 0xEAA127FA);
        c = HH(c, d, a, b, x[k+3],  S33, 0xD4EF3085);
        b = HH(b, c, d, a, x[k+6],  S34, 0x4881D05);
        a = HH(a, b, c, d, x[k+9],  S31, 0xD9D4D039);
        d = HH(d, a, b, c, x[k+12], S32, 0xE6DB99E5);
        c = HH(c, d, a, b, x[k+15], S33, 0x1FA27CF8);
        b = HH(b, c, d, a, x[k+2],  S34, 0xC4AC5665);
        a = II(a, b, c, d, x[k+0],  S41, 0xF4292244);
        d = II(d, a, b, c, x[k+7],  S42, 0x432AFF97);
        c = II(c, d, a, b, x[k+14], S43, 0xAB9423A7);
        b = II(b, c, d, a, x[k+5],  S44, 0xFC93A039);
        a = II(a, b, c, d, x[k+12], S41, 0x655B59C3);
        d = II(d, a, b, c, x[k+3],  S42, 0x8F0CCC92);
        c = II(c, d, a, b, x[k+10], S43, 0xFFEFF47D);
        b = II(b, c, d, a, x[k+1],  S44, 0x85845DD1);
        a = II(a, b, c, d, x[k+8],  S41, 0x6FA87E4F);
        d = II(d, a, b, c, x[k+15], S42, 0xFE2CE6E0);
        c = II(c, d, a, b, x[k+6],  S43, 0xA3014314);
        b = II(b, c, d, a, x[k+13], S44, 0x4E0811A1);
        a = II(a, b, c, d, x[k+4],  S41, 0xF7537E82);
        d = II(d, a, b, c, x[k+11], S42, 0xBD3AF235);
        c = II(c, d, a, b, x[k+2],  S43, 0x2AD7D2BB);
        b = II(b, c, d, a, x[k+9],  S44, 0xEB86D391);
        a = addUnsigned(a, AA);
        b = addUnsigned(b, BB);
        c = addUnsigned(c, CC);
        d = addUnsigned(d, DD);
      }
      var tempValue = wordToHex(a) + wordToHex(b) + wordToHex(c) + wordToHex(d);
      return tempValue.toLowerCase();
    }
  });
})(jQuery);