Re: [Gnumed-devel] GNotary

[Tim Churches]

Sebastian Hilbert wrote:
> On Tuesday 30 August 2005 02:23, Syan Tan wrote:
> 
>>the problem with the networked gnotary idea seemed to be uptake : would
>>people who ran gnotaries always be independent ?
> 
> 
>>Hashing the logs and publishing it in a paper seems to be a good idea. At a 
> document level, if the document was a program and the program was 
> obfuscatable, and the hash was md5 , then you could do the
>>2-documents-in-1-with-switching-on-the-identically-hashing-appended-block
>>attack.

Yes, but the Daum and Lucks attack (2 documents-in-one), although
clever, is trivial to discover and now that it is described, every
document whcih is a programme (i.e Postscript, PDF, MS-Word, OpenOffice
doc etc etc - needs to be inspected using a byte editor to check for the
attack, and not just printed out.

> The hash is not md5 nut sha256 and ripmd160. I hope this makes a differences. 
> If not. Tough luck. 


SHA256 is thought to be quite safe against both colision and pre-image
attacks for now.

Tim C