3 ms·
Even if you need a real entropy-based RNG, e.g. for key generation, you need to gather entropy once at the beginning to seed the RNG. Then running RNG does not
by pkolaczk 9y ago
Even if you need a real entropy-based RNG, e.g. for key generation, you need to gather entropy once at the beginning to seed the RNG. Then running RNG does not need any more entropy, so your hairdryer trick won't work. A common myth I hear is that "entropy" gets "depleted" during RNG operation, but in fact it does not. You only need enough bits of entropy once at the beginning, equal to the internal RNG state length.
- the_stc 9y agoStrong RNG designs re-seed to deal with compromise or poor seeding. That way if an attacker has temporary read access they do not permanently compromise the system going forward. Or if on boot you are in a compromised or low entropy environment the system will improve over time. Perhaps the utility of this is arguable. If an attacker is able to see your private RNG state then it is most likely game over. But it is a cheap operation with little downside and again, designs like Yarrow put considerable time into thinking it through.