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I could not find any definitive material about this topic, but when is it safe to use weak random number generators?
I would say:
* Generating random passwords - no
* Generating salt - no
* Jitter in a Retry Strategy - yes
What rules can we apply here?
"Strong" and "weak" is a sliding scale between indifference and tin-foil paranoia. Plenty of low-end embedded devices have questionable rng's but it's enough for them to make tls requests.
In many modern cryptosystems keys are ephemeral, there's a relatively small window to exploit weak rng's knowing the full state of the system. Long-lived keys are a different story, especially those generated soon after booting.
> Generating salt - no
A salt can be an incrementing number that is publicly known, they are not required to be secret. Using email as a salt is perfectly fine and poses no risk.
If there is a benefit to guessing the random number, then use a secure random number generator. Anything related to passwords, private keys, or anything you expect to be reasonably hard to guess, use a secure number generator.
When there is nothing to be gained from guessing the random number (to the point where you could just hardcode it, then it is safe to use a weak random number generator. Examples would be randomizing background images in a website header or picking a random quote of the day from a list. If there is a benefit to guessing the random number, then use a secure random number generator. Anything related to passwords, priva…
Noise generation, fuzzing, map/terrain or procedural generation in games, etc where you need randomness and someone replicating the same sequence isn't a threat
When there is nothing to be gained from guessing the random number (to the point where you could just hardcode it, then it is safe to use a weak random number generator. Examples would be randomizing background images in a website header or picking a random quote of the day from a list. If there is a benefit to guessing the random number, then use a secure random number generator. Anything related to passwords, priva…
Weak generators can also cause trouble in non-security-related applications. Monte Carlo simulations or integrations run with generators that don't truly randomly sample with respect to the underlying structure of the problem can go quite badly wrong. This usually requires a truly awful generator, but you'd be surprised what can happen. These days there is really no excuse to use anything worse than the Mersenne Twis…
It's to thwart rainbow tables and ensure unique hashes for users with the same passphrase.
dd if=/dev/urandom bs=8mb of=/dev/sda