I'd start from 2013.58. It's mostly a case of search/replace of function calls, though mp_init is a bit different I think (it allocates whereas the straight libtommath version doesn't?). Take a look at https://secure.ucc.asn.au/hg/dropbear/file/75509065db53/ecdsa.c#l169 - the ltc_mp variable is set up at https://secure.ucc.asn.au/hg/dropbear/file/75509065db53/crypto_desc.c#l71 so it could be set to tfm_desc instead.
Tomsfastmath 0.12 would be best from libtom.org Cheers, Matt On Sat, May 25, 2013 at 10:01:16AM -0500, William Welch wrote: > Thank you for your reply. > > If I were to attempt to add support for tomsfastmath, using ltc_mp as you > described, which version of dropbear should I start from? And where should > I obtain the tomsfastmath library? > > Thank you, > > William > > > > On Sat, May 25, 2013 at 3:41 AM, Matt Johnston <m...@ucc.asn.au> wrote: > > > 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 <bvwe...@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 > >> > >>