If you want to defend against hijackings, the problem you're trying to solve is one that programmers know well: the buffer overflow attack.
In a buffer overflow attack, someone gives a program much more data than it was expecting. The data is too long for the memory allocated for it and overflows into the memory occupied by the program itself. Suddenly the computer is running the attacker's code.
In a hijacking, the same thing happens to a plane. A plane has two separate spaces, one for the people carried on it, and one for the people who control it. A hijacking happens when passengers overflow into the cockpit from the cabin. What was cargo is now in control. By promoting themselves from data to code, hijackers on September 11th promoted box-cutters into 400,000 lb. incendiary bombs.
In a buffer overflow attack, someone gives a program much more data than it was expecting. The data is too long for the memory allocated for it and overflows into the memory occupied by the program itself. Suddenly the computer is running the attacker's code.
In a hijacking, the same thing happens to a plane. A plane has two separate spaces, one for the people carried on it, and one for the people who control it. A hijacking happens when passengers overflow into the cockpit from the cabin. What was cargo is now in control. By promoting themselves from data to code, hijackers on September 11th promoted box-cutters into 400,000 lb. incendiary bombs.