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Subject: Re: [boost] Boost.Uuid and header-only support
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2017-11-05 14:08:28

> So the initialization of the mersenne twister is expensive, so if you
> do it once and then reuse it, it is much more efficient than going to
> Wincrypt.

Mersenne is only fast on x86/x64. It is dog slow on every other CPU.

Also, I hate to be pedantic, but Mersenne is not cryptographically
secure. UUIDs ought to be generated from a crypto-strong source unless
the end user specifically asks for otherwise.

On Windows, that's RtlGenRandom() which is rand_s() in recent MSVC's. On
POSIX that is /dev/urandom or /dev/random depending on the POSIX flavour.

If you want something faster, Blake2b is crypto strong and fast on all
modern CPUs. Just need to seed it with a random seed, and you're happy.
Failing that, really recent CPUs can do SHA256 in hardware, but they
have tiny market penetration currently. You can, of course, use any AES
hardware offload also as a randomness generator, that has much wider
support in CPUs.


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