On 4/25/19 5:14 AM, Lennart Poettering wrote:
For the hashtable seeds we use classic /dev/urandom (i.e. entropy from a possibly non-initialized pool) since it's OK if those seeds are crappy initially, as long as they get better over time, since we reseed if we see too many hash collisions.
I thought that hashing would be fine with a completely predictable generator, as long as the sequence itself is not correlated, i.e. it would be OK if the sequence used for hashing was the same on every system.
Of course that particular sequence might lead to collisions, but then another uncorrelated but completely predictable sequence should fix that. In other words, it could be seeded from a constant table like [1,2,3,4,.....], just as well as from /dev/urandom regardless of its entropy.
My point here is that actual entropy of the seeding is irrelevant, at all times---would you agree?
That leaves the invocation IDs---the UUIDs need to be random to be truly Universally Unique, but a limited entropy system is implicitly isolated, so maybe the limited UUIDs could be seen as Universal in its very small Universe. What is the time duration of the original invocation IDs? What are the negative implication of the initial UUIDs being less random than the subsequent ones?
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