Trapdoor function

A trapdoor function is like a secret door that changes the way something works when you open it. Imagine a door in a house that can only be opened using a secret code. That's like a trapdoor function-- something special must be used to unlock it and you can open it to get access to things that were hidden before. Trapdoor functions are used in computer security to keep data safe. When the correct secret code is used, the trapdoor opens and allows people access to the data.