Matija Grabnar wrote: > Paul J Stevens wrote: >> and you can select >> the hash(es) you trust not to generate collisions. > Any hash you choose (as long as it shorter than the messages) WILL > generate collisions. It is a mathematical fact. You can not represent > all possible attachments with a short hash value. > (If you could, it wouldn't be a hash algorithm, it would be a > compression algorithm ;-)
I think I understand the math. Adding support for stronger hashes, and compound hashes was done mostly to take the pressure off. > I re-iterate: regardless of which digest algorithm is chosen, the code > MUST be able to > detect and correctly handle collisions. Collisions WILL occur, > regardless of the algorithm > chosen. It is a mathematically provable fact. The basic concept of single-instance storage relies on being able to identify unique blobs. Using a hash is one way of quickly generating them. Detecting and dealing with collisions can be done without too much loss in performance, but it will take some really care and I wont rush it if you dont mind. -- ________________________________________________________________ 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
