Next, write a recursive procedure, Add And Verify that performs the decryption, and checks if the decryption is valid. Add And Verify takes as input an address in $a0 for the encrypted string, an address in $a1 for the decrypted string, and a key K in $a2. Add And Verify (eventually, after performing all recursions) returns in $v0 the value of 1 if the decrypted message is a valid. Otherwise, $v0 is set to 0. Add And Verify will also use $v1 during the recursive process to store the carry bit. Since its a recursive procedure, it should operate as follows:.