Thats not true. Every time when you hash something what is bigger than your returned hash, there can be collision. This hash thing was talked alot before and in that time I offered solution that first slice that message to small parts and then select example first and last part. Hash both of them and thats it, almost impossible to get collision. It's still possible, but change is very very small. So to be safe, there must be at least 2 full hash.
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Vladimir Likhachev Sent: Saturday, December 29, 2007 8:33 AM To: DBMail mailinglist Subject: RE: [Dbmail] Re: DBMail 2.3.0 released Maybe, composite 2-column unique key (mime part size) and (mime part SHA1/any other hash) is a suitable solution? Same hash for same message size is really impossible, but for different message size it can occur. _____ > Date: Fri, 28 Dec 2007 18:17:46 +0100 > From: [EMAIL PROTECTED] > To: [email protected] > Subject: Re: [Dbmail] Re: DBMail 2.3.0 released > > Matija Grabnar wrote: > > Aaron Stone wrote: > >> I'm a big fan of double digest. I don't think the algorithm matters much, > >> just as long as the two are very different. Even just MD5 and SHA1 should > >> be plenty good, IMHO. > >> > > No, not more than some checksum that was as long as the sum of the two > > checksums you were using. > > I've decided to offer some relief for those concerned. I'm adding > libmhash as a build requirement, but that will add a lot of hashing > algorithms. > > By default dbmail will use SHA1 hashing for generating unique-ids per > mime part. But dbmail will support using any algo supported my mhash, > and you'll be able to do single or double digests, and you can select > the hash(es) you trust not to generate collisions. Of course, after you > change the hash(es) the ids in the mimeparts and partlists tables will > have to be recalculated and updated, so dbmail-util will have to support > that. And it will be up to the DBA to make sure the ID fields are wide > enough to hold the keys. > > > > > > -- > ________________________________________________________________ > Paul Stevens paul at nfg.nl > NET FACILITIES GROUP GPG/PGP: 1024D/11F8CD31 > The Netherlands________________________________http://www.nfg.nl > _______________________________________________ > DBmail mailing list > [email protected] > https://mailman.fastxs.nl/mailman/listinfo/dbmail _____ Express yourself instantly with MSN Messenger! MSN <http://clk.atdmt.com/AVE/go/onm00200471ave/direct/01/> Messenger
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