Uses too much entropy (Debian Bug #343085)

Andreas Metzler ametzler at
Fri Jan 4 19:07:36 CET 2008

On 2008-01-04 Simon Josefsson <simon at> wrote:
> Andreas Metzler <ametzler at> writes:

> > On 2008-01-04 Simon Josefsson <simon at> wrote:
> > [...]
> >>   2) To make exim link to and call libgcrypt's functions to read and
> >>      update a random seed file instead?
> > [...]
> >> For simplicity and non-experimentalness, I would recommend 2).  I can
> >> assist in implementing this in exim, if that would help.  We'd
> >> definitely need a good example of how to do this in the gnutls manual
> >> anyway.
> > [...]

> > Well, the basic patch for testing seems to be this one, basically
> > identical to the skeleton you described. I gets down entropy-usage
> > for a single STARTTLS to <300 bits from > 3000. 

> Nice.  How much does a similar server consume using openssl?  Do openssl
> used by exim use a seed file?


testing with a exim linked against OpenSSL I get *slightly* less
entropy usage (235 vs 289 bits in the first testrun) when connecting
with swaks (perl/OpenSSL).

These numbers were generated with the most simple method possible. -
Watch /proc/sys/kernel/random/entropy_avail when STARTTLSing from
localhost. Then STARTTLS from localhost to a remote server to find out
how much of the the total entropy usage was generated by the client,
instead of the server.

OpenSSL does not safe any random seed.
cu andreas
`What a good friend you are to him, Dr. Maturin. His other friends are
so grateful to you.'
`I sew his ears on from time to time, sure'

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