On Sun, Apr 28, 2002 at 01:06:10PM +1000, Donovan Baarda wrote: > On Sat, Apr 27, 2002 at 03:32:47PM -0700, Martin Pool wrote: > > On 27 Apr 2002, Donovan Baarda <[EMAIL PROTECTED]> wrote: > > > G'day, > > > > > > I've been working on a Python interface to librsync and have noticed that it > > > uses md4sum code borrowed from Andrew Tridgell and Martin Pool that comes > > > via rsync and was originally written for samba. > > > > Tridge recently discovered a bug in that code that probably does not > > weaken the digest, but that may make it incompatible with standard > > MD4. Basically, tail-extension is not properly carried out for blocks > > that are a multiple of 64 bytes in size. > > This would be nealy all blocks, as everyone would be using 2^n sized blocks > where n>5. If you meant to say "...that are _not_ multiple of 64 bytes...", > then I would dare to suggest fixing this would not hurt anybody, but > definitely record the affects. > > > I haven't had a chance yet to check how this affects rsync. If it > > does, I suppose we should evolve the protocol to fix it. > > > > There's not meant to be anything special about it. One of my TODO > > items was to replace it with a faster implementation. > > I'm not sure how the RSA implementation compares speed-wise, but given it is > more "correct", would there be major objections to replacing the samba md4 > with the RSA one in librsync? I guess I should benchmark and publish > results...
Ok, preliminary results are in. Because I'm primarily interested in Python interface stuff at the moment, I chose to make my benchmark by hacking together swig wrappers for the libmd md4c.c and the librsync mdfour.c, and whipping up a python test rig. The wrappers should have identical overheads. I used pre-generated random data for the input. The results for a Celeron-366 doing 10K md4sums on 4K blocks of random data are; libmd 3.1secs, librsync 2.5secs. Both gave identical checksum results so the bug Tridge found didn't rear it's head. Conclusion: the librsync md4 is pretty fast. However, it was also slightly harder to swig-wrap in isolation from the rest of librsync, as it had a few tie-ins with the rs_trace stuff. -- ---------------------------------------------------------------------- ABO: finger [EMAIL PROTECTED] for more info, including pgp key ---------------------------------------------------------------------- -- To unsubscribe or change options: http://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.tuxedo.org/~esr/faqs/smart-questions.html
