Re: 64bit MAC addresses and SLAAC

[Alexandre Petrescu <[e-mail]>]

Le 18/06/2020 à 17:31, Philip Homburg a écrit :
>> We looked for the place in linux which forces the 64bit limit in 
>> SLAAC.
> 
> Which make sense, because that is what the RFC says.
> 
>> We found it and we wondered what to put in these - potentially 66 -
>> bits of an IID?   The immediate thought was to put there random
>> numbers. These random numbers seemed natural to several of us.  And
>> they offer privacy.
> 
> I'm sure that if SLAAC is updated to allow other lengths, some
> consideration will be given to generating IIDs. However, at the
> moment SLAAC is 64-bit even if some implementations try to be more
> flexible.
> 
>> If we put random numbers in there then for years again the users 
>> will find it difficult to remember those scrambled numbers when 
>> typing ifconfig.
> 
> That is the nature of SLAAC. You need an IID that has a very high
> probabily of being unique. So you need enough random bits.

Indeed it seems so that nature.  If one wants numbers that are likely to
be unique, probably random numbers are the easiest and safest choice.

Maybe a 14 volume Oxford dictionary indexed by a random pointer would
still issue words likely to be unique.

Probably that kind of generation is more particular to DHCPv6, or so.

Alex

> 
> If you want easy to remember addresses, go for DHCPv6.
> 
>> If we put random numbers in there then for years again people will 
>> look for easy to use, license-free, platform-independent, high 
>> performance, speedy, C standard, less energy consuming,
>> almost-true random, primitives to call; and their seeds.
> 
> It is not to hard to find an SHA2-HMAC implementation.
>