The fact that he uses prime factorization as his test for "can use you time turner to solve computationally hard problems" is evidence that he did know about prime number based cryptography, not strong evidence, but evidence still, since the prime-based crypto is the most common reason people are interested in having fast ways to factor primes.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 116.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)