New Linear Cryptanalysis of Chinese Commercial Block Cipher Standard SM4

Algorithm 1

Search algorithm for iterative linear approximation of 3-round SM4.

  for   to 2  do

  for   to   do

    for all   do

      find all input masks indexed by from , and store in

      for   to   do

       find all input masks indexed by from , and store in

       for   to   do

         find all input masks indexed by from , and store in

         for   to   do

           for   to   do

           end for

           for   to   do

           end for

           if    then

             return  

             // 3-round iterative linear approximation

           else

             continue.

           end if

        end for

       end for

     end for

   end for

  end for

 end for