There is a "privacy hole" from using the MAC address. (Read it in the WIKI article someone else posted). Probably, it would be better to use a one way hash of the MAC address. > -----Original Message----- > From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general- > owner@xxxxxxxxxxxxxx] On Behalf Of Chris Travers > Sent: Wednesday, July 27, 2005 2:27 PM > To: Magnus Hagander; pgsql-general > Subject: Re: GUID for postgreSQL > > Magnus Hagander wrote: > > >> > > > >At least on Windows, the GUID is derived in part from the computers > >primary MAC address. No, it's not a guarantee, but it's pretty unlikely > >:-) > > > > > The danger is not that the MAC address will be duplicated, but that > other factors will lead to an MD5 collision. > > Unless you can show me that there is a 1:1 correspondence of all > possible unique factors going into the GUID generation and the output, > then I will say it is still no guarantee. > > Just because two documents or files have the same MD5 doesn't mean that > they are the same files either. I.e. you can't go searching all files > by MD5 checksums and expecting to find the right one. OTOH, MD5 > provides reasonable assurance that any given file (once you know its > intended MD5) has not been tampered with. I.e. MD5 is not meant to > preclude collisions, but rather it is meant to preclude *intentional* > collisions. Similarly, if we want a guaranteed uniqueness to a GUID we > have to have some sort of unique string to the GUID prepended to it (not > merely used in a hash). > > So you could use the Mac address of the machine, I guess, if you wanted > to.... > > Best Wishes, > Chris Travers > Metatron Technology Consulting > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
