It's been a while since I've looked at the literature on RSA prime generation, but I seem to remember that picking a random starting point and iterating until you find a prime is discouraged because primes aren't evenly distributed so key generation timing could reveal some information about your starting point and eventual prime choice.
I'm not sure how realistic of an issue this is given the size of the primes involved. Even if an attacker can extract sensitive enough timing information to figure out exactly how many iterations were required to find a 1024 bit prime from a 1204 bit random starting point, I'm not aware of a good way to actually find either value. You do also introduce a bias since you're more likely to select prime numbers without a close neighbor in the direction you are iterating from, but again I'm not sure how practical an attack on this bias would be.
Still, to avoid any potential risk there I seem to remember best practice being to just randomly generate numbers of the right size until you find a prime one. With the speed of modern RNGs, generating a fresh number each time vs iterating doesn't seem like a significant penalty.
I'm not sure how realistic of an issue this is given the size of the primes involved. Even if an attacker can extract sensitive enough timing information to figure out exactly how many iterations were required to find a 1024 bit prime from a 1204 bit random starting point, I'm not aware of a good way to actually find either value. You do also introduce a bias since you're more likely to select prime numbers without a close neighbor in the direction you are iterating from, but again I'm not sure how practical an attack on this bias would be.
Still, to avoid any potential risk there I seem to remember best practice being to just randomly generate numbers of the right size until you find a prime one. With the speed of modern RNGs, generating a fresh number each time vs iterating doesn't seem like a significant penalty.