@phnt >was a suspected backdoor by the NSA is specifically because the NSA didn't disclose how they got the number.
Oh, I did wonder about that. so it's kind of similar to finding out the prime factor of a number in that sense. like NSA knowing a prime factor and not sharing it, people can't find it out but the NSA can (I am not entirely sure how this works so i think you'll correct me that it isn't a prime factor in stuff like RSA encryption and i'm confusing this for something else)