the code is just an illutration, you can understand what’s going on without understanding code.
It’s a demonstration of that time that they added a backdoor to the login program. They supplied source code to the login program and upon recompile, the login program still had a backdoor. So the compiler was the thing inserting the backdoor.
With the source to the compiler you can recompile the compiler… then recompile the login program… only to find the login program still has the back door, Even though the back door is not in the source code.
How? The compiler knows when it is compiling both itself and the login program.
This paper, from 1984, in the context of elliptic curve crpto weaknesses, if you are at all interested in technology, should shake you to your very core?
Think about the implications.