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  #1  
Old 07-15-2020, 16:14
wassim_ wassim_ is offline
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Idenitfying a cryptographic algorithm

I need help identifying this decryption algorithm, the argument "s" in the function d3 is the encrypted string.
If this is a known algorithm, I would like to get the algorithm to write the encrypted string "s" myslef.

Code:
function d3(s)
   {
      var _loc4_ = s.substr(0,11);
      var _loc9_ = Number(_loc4_.substr(10,1));
      var _loc3_ = Number(_loc4_.substr(_loc9_,2));
      var _loc7_ = s.substr(22,_loc3_);
      var _loc10_ = String(s.substr(11,11));
      var _loc8_ = Number(s.substr(21,1));
      var _loc6_ = Number(s.substr(11 + _loc8_,2));
      var _loc5_ = s.substr(22 + _loc3_,s.length - (22 + _loc3_));
      return this.d(_loc7_,_loc6_,_loc5_);
   }
   function d(a, k, s)
   {
      return this.t(a,- k,s);
   }
   function t(a, k, s)
   {
      var _loc8_ = undefined;
      var _loc3_ = "";
      var _loc4_ = s.length;
      var _loc2_ = 0;
      while(_loc2_ < _loc4_)
      {
         _loc3_ = _loc3_ + this.r(a,s.charAt(_loc2_),k);
         _loc2_ = _loc2_ + 1;
      }
      return _loc3_;
   }
   function r(a, c, k)
   {
      var _loc2_ = a.indexOf(c);
      var _loc1_ = a.length;
      if(_loc2_ != -1)
      {
         return a.charAt((_loc2_ + k + _loc1_) % _loc1_);
      }
      return c;
   }
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  #2  
Old 07-15-2020, 22:15
chants chants is offline
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I think if you rewrote and cleaned up that code, it would be easier. It appears not as a much of a cryptographic algorithm as some simple string manipulation code. It can be a single function with a loop having a single condition inside of it. After cleaning it up, figuring out how to invert the function should be somewhat straight forward.
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