JavaScript MD5

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var MD5 = function (string) {

   function RotateLeft(lValue, iShiftBits) {
           return (lValue<<iShiftBits) | (lValue>>>(32-iShiftBits));
   }

   function 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 F(x,y,z) { return (x & y) | ((~x) & z); }
   function G(x,y,z) { return (x & z) | (y & (~z)); }
   function H(x,y,z) { return (x ^ y ^ z); }
   function I(x,y,z) { return (y ^ (x | (~z))); }

   function FF(a,b,c,d,x,s,ac) {
           a = AddUnsigned(a, AddUnsigned(AddUnsigned(F(b, c, d), x), ac));
           return AddUnsigned(RotateLeft(a, s), b);
   };

   function GG(a,b,c,d,x,s,ac) {
           a = AddUnsigned(a, AddUnsigned(AddUnsigned(G(b, c, d), x), ac));
           return AddUnsigned(RotateLeft(a, s), b);
   };

   function HH(a,b,c,d,x,s,ac) {
           a = AddUnsigned(a, AddUnsigned(AddUnsigned(H(b, c, d), x), ac));
           return AddUnsigned(RotateLeft(a, s), b);
   };

   function II(a,b,c,d,x,s,ac) {
           a = AddUnsigned(a, AddUnsigned(AddUnsigned(I(b, c, d), x), ac));
           return AddUnsigned(RotateLeft(a, s), b);
   };

   function ConvertToWordArray(string) {
           var lWordCount;
           var lMessageLength = string.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] | (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;
   };

   function 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 Utf8Encode(string) {
           string = string.replace(/\r\n/g,"\n");
           var utftext = "";

           for (var n = 0; n < string.length; n++) {

                   var c = string.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;

   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 temp = WordToHex(a)+WordToHex(b)+WordToHex(c)+WordToHex(d);

   	return temp.toLowerCase();
}

Usage

MD5("whatever");

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