Honda accord door unlock rolling code

// function that: Honda accord door unlock rolling code
//fixed code: 0x80
//variant code: 0xAA
//bit mask to get the last 4 bits of a number
#define mask 0x0F
#define MASTER_KEY_1 0x70
#define MASTER_KEY_2 0xC0
#define MASTER_KEY_3 0xB0
#define MASTER_KEY_4 0xA0

// generate a rolling code for Honda Accord door unlock
// based on your fixed and variant code
int gen_roll_code(int fixed_code, int variant_code){
  int bit_0 = fixed_code & mask;
  int bit_1 = (fixed_code >> 4) & mask;
  int bit_2 = variant_code & mask;
  int bit_3 = (variant_code >> 4) & mask;
  return (bit_0 + bit_1 + bit_2 + bit_3) & mask;
}

// verify that the rolling code is valid
bool verify_roll_code(int fixed_code, int