Project looking glass is cryptography.
If I encrypt data today, I get two keys, yes?
If I give you those keys you will be able to decrypt said data, yes?
And the way cryptology works, you will always get the exact same result, if you have the keys, correct?
So what happens if someone encrypts data 1000 years from now?
They get two keys yes?
And those two keys will, and can only, give the original message, yes?
So lets imagine that super spook encrypts data 1000 years from now, he will get two keys, yes?
So what happens if I brute force all combinations of keys today?
What happens if I crack super spooks keys?, today?
Don't I get the same data, yes or no?