slow logins -- some data for comparison

[Matt Johnston]

Hi,

I think the solution is to use tomsfastmath instead. There was a patched version posted a while ago on this list. Eventually I'd like to have Dropbear able to build against either tomsfastmath (for speed) or libtommath (for portability) using the ltc_mp mechanism in libtomcrypt.

There's also ECC support nearly complete in the 'ecc' mercurial branch. That's a few times faster than normal kexdh. It adds around 30kB to binary size on x86. That should make it into the next Dropbear release, though only will help for recent OpenSSH peers.

Matt

William Welch <bvwelch at gmail.com> wrote:
>Greetings,
>
>First -- thank you for dropbear!  I have enjoyed using dropbear on
>various
>smallish systems for years now!
>
>But I have a problem with a specific system -- admittedly it is rather
>slow
>-- only 50 BogoMips according to the linux kernel. It is a Microblaze.
>
>I use the Buildroot system for many different routers and other small
>systems here.  I have compared different versions of dropbear, against
>openssh.
>
>My issue is with the server mode -- sshd --  I note that on dropbear
>0.52
>(which I happen to run on other routers here), I can connect from my
>ubuntu
>or mac, to dropbear sshd, in about 45 seconds.  This is having disabled
>the
>RSA host key, and already generated the DSS host key.   But on more
>recent
>versions of dropbear, e.g. 2013.58, several minutes elapse without a
>connection.
>
>In contrast, switching to openssh in buildroot, and also disabling the
>RSA
>host key, connection time is 5 to 10 seconds!  Unfortunately, the
>openssh
>has a huge 'footprint' in the flash filesystem that I would rather
>avoid.
>
>The issue seems to be in the key exchange ( I can watch this by doing
>'ssh
>-v ' from my client connection).  Meanwhile, running 'top' on my
>Microblaze
>shows near 100% cpu used.  the debug message is: expecting
>SSH2_MSG_KEXDH_REPLY
>
>Buildroot has the gnu cross tool chain set to 'optimize for size' in
>all
>cases.
>
>Suggestions welcome!
>
>thank you,
>
>William
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