I'm currently discussing a security topic with some of my classmates.
A cryptographic PRNG typically provides backtracking resistance if an adversary that compromises the internal PRNG state cannot distinguish previously generated values from random values.
Let's assume I use an invertible PRF as PRNG (e.g. AES in CTR mode with a true random key). Then this in general does not provide backtracking resistance since, after obtaining the internal state, I can calculate the previous output using the inverted PRF.
Now let's assume that I regularly reseed my PRNG, like for example every second. Does it then provide backtracking resistance or not?
We have now two opinions:
The PRNG does not provide backtracking resistance since it is possible to recover previous values within the compromised reseed interval.
The PRNG provides backtracking resistance since values beyond the reseed interval can only be guessed with negligible probability
Can someone explain who is right and why?
Best regards, Matt