Improvements for Finding Impossible Differentials of Block Cipher Structures

Algorithm 2

Function UpdateVector.

//  Update the variable vector    according to the variable    where    is the value

of the  th variable in  .   is the array of constraints.

input: the variable vector , the constraint array , .

output: A boolean flag indicates if the update procedure success.

(1) flag true;

(2) foreach    do

(3) ; ;

(4) if    is equal to    then

(5) if    is not 0  then

(6) flag false; //  Ex.   but  , a contradiction.

(7) return  flag;

(8) else if    is 0 and    is ? then

(9) if    is not 0 then flag false;

(10) return  flag;

(11) end

(12) ;  ;

(13) else if    is a nonzero value  then

(14) ;  ;

(15) end

(16) else if    is equal to    then

(17) if    is not 0 then flag false

(18) return  flag;

(19) else if    is ? and    is 0 then

(20) ;  ;

(21) end

(22) end

(23) end

(24) return  flag;