title: How to decode/decrypt MD5 encryption using Java
body: <p>I am using the ExtJS framework. I have a MD5 function in <strong><em>JavaScript</em></strong> to encrypt some JSON. My backend uses Java so I wanted to know how to decrypt an MD5 Javascript encryption using <strong><em>Java</em></strong>?</p>
  
  <p>Here is the JS equiv of MD5 function that I am using:</p>
  
  <pre><code>Ext.util.MD5 = function(s,raw,hexcase,chrsz) {
          raw = raw || false;     
          hexcase = hexcase || false;
          chrsz = chrsz || 8;
  
          function safe_add(x, y){
                  var lsw = (x &amp; 0xFFFF) + (y &amp; 0xFFFF);
                  var msw = (x &gt;&gt; 16) + (y &gt;&gt; 16) + (lsw &gt;&gt; 16);
                  return (msw &lt;&lt; 16) | (lsw &amp; 0xFFFF);
          }
          function bit_rol(num, cnt){
                  return (num &lt;&lt; cnt) | (num &gt;&gt;&gt; (32 - cnt));
          }
          function md5_cmn(q, a, b, x, s, t){
                  return safe_add(bit_rol(safe_add(safe_add(a, q), safe_add(x, t)), s),b);
          }
          function md5_ff(a, b, c, d, x, s, t){
                  return md5_cmn((b &amp; c) | ((~b) &amp; d), a, b, x, s, t);
          }
          function md5_gg(a, b, c, d, x, s, t){
                  return md5_cmn((b &amp; d) | (c &amp; (~d)), a, b, x, s, t);
          }
          function md5_hh(a, b, c, d, x, s, t){
                  return md5_cmn(b ^ c ^ d, a, b, x, s, t);
          }
          function md5_ii(a, b, c, d, x, s, t){
                  return md5_cmn(c ^ (b | (~d)), a, b, x, s, t);
          }
  
          function core_md5(x, len){
                  x[len &gt;&gt; 5] |= 0x80 &lt;&lt; ((len) % 32);
                  x[(((len + 64) &gt;&gt;&gt; 9) &lt;&lt; 4) + 14] = len;
                  var a =  1732584193;
                  var b = -271733879;
                  var c = -1732584194;
                  var d =  271733878;
                  for(var i = 0; i &lt; x.length; i += 16){
                          var olda = a;
                          var oldb = b;
                          var oldc = c;
                          var oldd = d;
                          a = md5_ff(a, b, c, d, x[i+ 0], 7 , -680876936);
                          d = md5_ff(d, a, b, c, x[i+ 1], 12, -389564586);
                          c = md5_ff(c, d, a, b, x[i+ 2], 17,  606105819);
                          b = md5_ff(b, c, d, a, x[i+ 3], 22, -1044525330);
                          a = md5_ff(a, b, c, d, x[i+ 4], 7 , -176418897);
                          d = md5_ff(d, a, b, c, x[i+ 5], 12,  1200080426);
                          c = md5_ff(c, d, a, b, x[i+ 6], 17, -1473231341);
                          b = md5_ff(b, c, d, a, x[i+ 7], 22, -45705983);
                          a = md5_ff(a, b, c, d, x[i+ 8], 7 ,  1770035416);
                          d = md5_ff(d, a, b, c, x[i+ 9], 12, -1958414417);
                          c = md5_ff(c, d, a, b, x[i+10], 17, -42063);
                          b = md5_ff(b, c, d, a, x[i+11], 22, -1990404162);
                          a = md5_ff(a, b, c, d, x[i+12], 7 ,  1804603682);
                          d = md5_ff(d, a, b, c, x[i+13], 12, -40341101);
                          c = md5_ff(c, d, a, b, x[i+14], 17, -1502002290);
                          b = md5_ff(b, c, d, a, x[i+15], 22,  1236535329);
                          a = md5_gg(a, b, c, d, x[i+ 1], 5 , -165796510);
                          d = md5_gg(d, a, b, c, x[i+ 6], 9 , -1069501632);
                          c = md5_gg(c, d, a, b, x[i+11], 14,  643717713);
                          b = md5_gg(b, c, d, a, x[i+ 0], 20, -373897302);
                          a = md5_gg(a, b, c, d, x[i+ 5], 5 , -701558691);
                          d = md5_gg(d, a, b, c, x[i+10], 9 ,  38016083);
                          c = md5_gg(c, d, a, b, x[i+15], 14, -660478335);
                          b = md5_gg(b, c, d, a, x[i+ 4], 20, -405537848);
                          a = md5_gg(a, b, c, d, x[i+ 9], 5 ,  568446438);
                          d = md5_gg(d, a, b, c, x[i+14], 9 , -1019803690);
                          c = md5_gg(c, d, a, b, x[i+ 3], 14, -187363961);
                          b = md5_gg(b, c, d, a, x[i+ 8], 20,  1163531501);
                          a = md5_gg(a, b, c, d, x[i+13], 5 , -1444681467);
                          d = md5_gg(d, a, b, c, x[i+ 2], 9 , -51403784);
                          c = md5_gg(c, d, a, b, x[i+ 7], 14,  1735328473);
                          b = md5_gg(b, c, d, a, x[i+12], 20, -1926607734);
                          a = md5_hh(a, b, c, d, x[i+ 5], 4 , -378558);
                          d = md5_hh(d, a, b, c, x[i+ 8], 11, -2022574463);
                          c = md5_hh(c, d, a, b, x[i+11], 16,  1839030562);
                          b = md5_hh(b, c, d, a, x[i+14], 23, -35309556);
                          a = md5_hh(a, b, c, d, x[i+ 1], 4 , -1530992060);
                          d = md5_hh(d, a, b, c, x[i+ 4], 11,  1272893353);
                          c = md5_hh(c, d, a, b, x[i+ 7], 16, -155497632);
                          b = md5_hh(b, c, d, a, x[i+10], 23, -1094730640);
                          a = md5_hh(a, b, c, d, x[i+13], 4 ,  681279174);
                          d = md5_hh(d, a, b, c, x[i+ 0], 11, -358537222);
                          c = md5_hh(c, d, a, b, x[i+ 3], 16, -722521979);
                          b = md5_hh(b, c, d, a, x[i+ 6], 23,  76029189);
                          a = md5_hh(a, b, c, d, x[i+ 9], 4 , -640364487);
                          d = md5_hh(d, a, b, c, x[i+12], 11, -421815835);
                          c = md5_hh(c, d, a, b, x[i+15], 16,  530742520);
                          b = md5_hh(b, c, d, a, x[i+ 2], 23, -995338651);
                          a = md5_ii(a, b, c, d, x[i+ 0], 6 , -198630844);
                          d = md5_ii(d, a, b, c, x[i+ 7], 10,  1126891415);
                          c = md5_ii(c, d, a, b, x[i+14], 15, -1416354905);
                          b = md5_ii(b, c, d, a, x[i+ 5], 21, -57434055);
                          a = md5_ii(a, b, c, d, x[i+12], 6 ,  1700485571);
                          d = md5_ii(d, a, b, c, x[i+ 3], 10, -1894986606);
                          c = md5_ii(c, d, a, b, x[i+10], 15, -1051523);
                          b = md5_ii(b, c, d, a, x[i+ 1], 21, -2054922799);
                          a = md5_ii(a, b, c, d, x[i+ 8], 6 ,  1873313359);
                          d = md5_ii(d, a, b, c, x[i+15], 10, -30611744);
                          c = md5_ii(c, d, a, b, x[i+ 6], 15, -1560198380);
                          b = md5_ii(b, c, d, a, x[i+13], 21,  1309151649);
                          a = md5_ii(a, b, c, d, x[i+ 4], 6 , -145523070);
                          d = md5_ii(d, a, b, c, x[i+11], 10, -1120210379);
                          c = md5_ii(c, d, a, b, x[i+ 2], 15,  718787259);
                          b = md5_ii(b, c, d, a, x[i+ 9], 21, -343485551);
                          a = safe_add(a, olda);
                          b = safe_add(b, oldb);
                          c = safe_add(c, oldc);
                          d = safe_add(d, oldd);
                  }
                  return [a, b, c, d];
          }
          function str2binl(str){
                  var bin = [];
                  var mask = (1 &lt;&lt; chrsz) - 1;
                  for(var i = 0; i &lt; str.length * chrsz; i += chrsz) {
                          bin[i&gt;&gt;5] |= (str.charCodeAt(i / chrsz) &amp; mask) &lt;&lt; (i%32);
                  }
                  return bin;
          }
          function binl2str(bin){
                  var str = "";
                  var mask = (1 &lt;&lt; chrsz) - 1;
                  for(var i = 0; i &lt; bin.length * 32; i += chrsz) {
                          str += String.fromCharCode((bin[i&gt;&gt;5] &gt;&gt;&gt; (i % 32)) &amp; mask);
                  }
                  return str;
          }
  
          function binl2hex(binarray){
                  var hex_tab = hexcase ? "0123456789ABCDEF" : "0123456789abcdef";
                  var str = "";
                  for(var i = 0; i &lt; binarray.length * 4; i++) {
                          str += hex_tab.charAt((binarray[i&gt;&gt;2] &gt;&gt; ((i%4)*8+4)) &amp; 0xF) + hex_tab.charAt((binarray[i&gt;&gt;2] &gt;&gt; ((i%4)*8  )) &amp; 0xF);
                  }
                  return str;
          }
          return (raw ? binl2str(core_md5(str2binl(s), s.length * chrsz)) : binl2hex(core_md5(str2binl(s), s.length * chrsz))     );
  };
  </code></pre>