Hi Iljitsch,
On Fri, 12 Sep 2003, Iljitsch van Beijnum wrote: > On vrijdag, sep 12, 2003, at 11:07 Europe/Amsterdam, George Gross wrote: > > > At the risk of triggering another firestorm of pro/con debate, is > > there any reason why the centrally assigned Global ID defined by > > hinden-ipv6-global-local-addr-02.txt could not be simply the low-order > > 40 > > bits of a SHA hash of a domain name? i.e. if you own the domain name, > > you > > get the IP-v6 global ID for "free"? This would side step the angst of > > setting up yet another global registry... > > Hm, with 2^40 possible prefixes and already something in the order of > 2^25 domains in use, I expect collisions will be a definite factor. In a parallel e-mail to Zefram, I offered an algorithm for probing for uniqueness, and then retrying. OTOH, if you merely want a genuinely local pseudo-random number, then the collision factor is moot. > I would also be interested in seeing how the SHA-1 algorithm holds up. > Anyone care to get a suitably large list of domain names (a million or > so) and do some statistics on the lower 40 bits of the associated > SHA-1 hash? SHA-1 has fairly strong hashing properties, even changing one bit in the input yields a reasonably diverse output. OTOH, I'm not a cryptographer, though I'll add that most of what I've heard about SHA-1 is that it is held in high regard. FYI, you may wish to dredge the IRTF CFRG e-mail archives for the thread with the Subject line of "one question about hash" that occured in July of this year. The good news about those 2^25 domain name holders is that they are the most likely consumers of this local IP-v6 address prefix, and they would immediately inherit their's for free without doing anything. > > It did occur to me that the domain name sellers are in a better > position to give out these prefixes than the traditional IP address > registries, though. Especially if you consider that they'd just be > selling domain names under c.f.ip6.arpa. :-) > Another implicit benefit is that every domain name holder already has a local IP-v6 prefix allocated on the shelf waiting for them. Musing outloud, I wonder how that could be leveraged to automatically compute the IP-v6 address of any IP-v4 endpoint for which you know the FQDN and your DNS query returned an IP-v4 address record. br, George -------------------------------------------------------------------- IETF IPv6 working group mailing list [EMAIL PROTECTED] Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------