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25 lines
1.1 KiB
Markdown
25 lines
1.1 KiB
Markdown
libent is a cross-platform wrapper around `getentropy(2)`. It exports
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one symbol, `ent_getentropy`, which expands to `getentropy` if the
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latter is available. Otherwise, it tries to use the next best source of
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entropy — `/dev/urandom` on *nix.
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### Why?
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`getentropy` is the wave of the future. It's the correct API for
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generating small amounts of entropy to create cryptographic keys or seed
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PRNGs. It's good and reasonable and true, it's on Linux, *BSD, and OS X,
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and it only took us fifty years of UNIX to get here.
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Sadly, it only just arrived, so nobody has it yet. It didn't land in
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Linux until glibc 2.25, which seems to only have made it into Debian 10.
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Once `getentropy` is everywhere you care about, you can just do a
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s/ent_//g on all the call sites and discard this shim.
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Admittedly, 90% of the motivation behind this was to fix the randomness
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shim in [Urbit](https://github.com/urbit/urbit).
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References:
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* [OpenBSD getentropy](https://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2)
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* [djb on entropy gathering](https://blog.cr.yp.to/20140205-entropy.html)
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