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Re: Tempfile vulnerabilities
From: lbudney-lists-bugtraq () NB NET (Len Budney)
Date: Thu, 3 Feb 2000 14:18:56 -0500


Theo de Raadt <deraadt () CVS OPENBSD ORG> wrote:

Crypto software which uses [/dev/random] devices should be doing
some kind of checking to make sure that they are getting at least
good entropy.

/dev/random will not emit bytes below some entropy threshold. Somebody
draining /dev/random amounts to a DOS attack; it will begin emitting at a
snail's pace, and users of /dev/random will contend for the scarce bytes.

If lower entropy is acceptable, /dev/urandom will invoke a PRNG to
keep emitting, even when the entropy pool is depleted. The output of
/dev/urandom passes the diehard tests reasonably well, and should be
acceptable for most non-cryptographic applications.

Of course, as Werner Koch already indicated, casual applications of
"random numbers" should not waste the entropy pool.

Len.


--
Bandwidth is bad for the same reason that most programs are so slow:
programmers _guess_ where the bottlenecks are rather than _profiling_.
                                -- Dan Bernstein



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