On Tue, 3 Jun 2003 [EMAIL PROTECTED] wrote:
> >I confess to being confused - though admittedly part of the blame for this >is my own ignorance. > >I remember a time when PGP was a command line application. The only >algorithms it used were IDEA (symmetric), RSA (assymetric) and MD5 (hash). I >came to trust these algorithms. > >Now these once-'standard' algorithms are no longer encouraged. The new >versions of PGP seem to prefer CAST instead of IDEA, DH/DSS instead of RSA, >and SHA-1 instead of MD5. > >So, could someone please tell me: > >(1) What is the justification for using these "new" algorithms instead of >the old ones? (A cynic might suggest that, since the "powers that be" >couldn't break the old algorithms, they encouraged the use of new ones that >they could. This probably isn't true, but I'm sure you can understand why >someone might think that). Well - Hans Dobbertin found hash collisions in MD5 and while I haven't heard much more, that's a toehold that somebody might be able to use to break it, and makes it vulnerable in some applications. SHA-1 is now considered better. IDEA is still a good cipher as far as I know, but PGP has been driven away from it in the US due to intellectual-property issues. Rather than continue with incompatible versions for use inside/outside the USA, they're switching to CAST (although this is causing more, rather than less, version incompatibilities). RSA is still good, as far as I know, and has been in the public domain worldwide since September 2001. But it had the same kind of IP issues as IDEA until that point, and several versions of PGP had to be produced that used a different asymmetric cipher for that reason. I don't know enough about DH/DSS specifically to comment further on its relative security, but RSA has had several scares and people are concerned that custom hardware (such as a million-qubit quantum computing device or Bernstein's matrix hardware factoring device) might cause insecurity in RSA _and_ be possible for someone to keep secret. And lots of people quit using RSA because they don't like the "big block of key" that it requires. >(2) What actually _IS_ DH/DSS? (I don't mean what do the initials it stand >for, I mean what actually is the algorithm?). I ask because I can understand >RSA, and implement it myself relatively straightforwardly, but I have not >been able to find an explanation, simple or otherwise, of what the DH/DSS >algorithm actually is, or of why it's hard to break. > >(3) Ditto CAST and SHA-1. for a good complete description of SHA-1 and a few others, try http://csrc.nist.gov/publications/fips/fips180-2/fips180-2.pdf (warning: link may be outdated). I don't have pointers to the other two offhand. Bear --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]