I played with this question for hours yesterday having fun and discoveries. It was what I call playtime. Thank you! As seen with other answers there are variables to meanings for words specifically truth and freedom.
Okay probably TMI. As seen to answer is firstly a matter of interpretation. A consequence is there are two abstract nouns – truth and freedom. An abstract noun “refers to something with which a person cannot physically interact” or is intangible. In this case of four categories it falls into ideas / concepts / ideals.
First is to change the question into a statement, which usually aims at becoming a thesis statement. The question above is two questions where one is true and one false. Thus we have as I interpret it:
Truth is a lock on freedom and needing a key. So, what is the key?
Truth is a key to freedom and not its lock. So, what is the lock?
I did decide the abstract freedom is like a door. It is a barrier that protects, can capture, and open inward and/or outward allowing access inside and/or outside. At this point it is a tangible and functional object only requiring a purpose for an action – opened, closed, and locked too.
Now we can explore ‘Truth’. If a tangible lock it operates the door. If a tangible key it operates the lock, which operates the door. In both cases it is functional while the former are paired and functional together. Occams razor (the Law of Parsimony) says “Entities should not be multiplied unnecessarily." Or, “when you have two competing theories that make exactly the same predictions (Freedom to become functional), the simpler one is the better."
Perhaps I am wrong, but it appears ‘Truth is a lock’ while the key remains an unknown. In this case the key is only necessary if the lock is locked, but the lock and door together are functional. Perhaps the key is free will, faith, or some such? Another perhaps is the door lock remains opened as long as there is liberty - to pass freely (Through the door) between inside and outside. They remain functional together. I dun'no . . . but, was fun :-)