6 ms·

A house may have multiple people living there, multiple devices, visitors, etc. You could track a person connecting through multiple locations by using their M

by mgbmtl 12y ago

A house may have multiple people living there, multiple devices, visitors, etc. You could track a person connecting through multiple locations by using their MAC address used to assign their IP. i.e. if I am connecting with my laptop from various places, my IP address will be roughly the same, only the network prefix will change.

rjsw 12y ago
A house could have multiple users, mine doesn't. I would maybe see turning on privacy addresses as part of a general "leaving home" script that also turned on other stuff like the firewall.
- RRRA 12y ago
  Time to participate in open wifi or a mesh network :-)
- ay 12y ago
  You are completely right. Privacy IPv6 address are an illusion when used in a household that has effectively an active /64 per subscriber. (Those who say "but IPv4..." last time my IPv4 address changed, was half a year ago). Anyway this is mostly a political give-in, that happens to also help ruggedize the rest of the stack (the relatively rapid change of privacy addresses uncovers more bugs than we'd otherwise find - so from that standpoint they're to be advocated). But privacy.. huh. Last IETF there was precisely this discussion that one might want to force a new /64 on themselves, and privacy addresses have nothing to do with that. (DHC WG, FWIW).
  - X-Istence 12y ago
    Comcast is more than willing to send you more than one /64 prefix if you ask for it!
    - ay 12y ago
      "effectively an active /64". Comcast folks did a ton of testing with the CPEs, and very very few could ask for anything than an active /64, that's why this qualifier :-) There's active (and pretty cool) work in the HomeNet IETF workgroup, with running code and all (http://www.homewrt.org/doku.php http://www.homewrt.org/doku.php) to make the multi-subnet home network a sane reality. But a different /64 from within the same /56 helps not much, and indeed to correctly reflect the spirit of the discussion in the DHC working group, would be to say "I want to be able to press a button and release my currently used allocation and get some completely new one, be it /48, /56 or whatever". Thanks for the correction!
- agwa 12y ago
  The proper solution is Stable Privacy addresses, recently standardized in RFC7217 [1]. The interface ID is essentially hash(secret || prefix || mac-address), so it stays the same when you're on the same network, but changes as soon as you go somewhere else. [1] https://tools.ietf.org/html/rfc7217 https://tools.ietf.org/html/rfc7217
  - cm2187 12y ago
    But that defeats the purpose of a privacy address. The idea is precisely not to use your address as a way to track individual users, like a cookie tattooed on your skin. I fail to see how a hash of the MAC address is better than the MAC address itself.
    - agwa 12y ago
      Because even with traditional privacy addresses, the first 64 bits of your address never change, and you can be tracked that way. If you happen to share those first 64 bits with many other people, then privacy addresses provide value, but that's simply not the case on your home network. Now keep in mind that a stable privacy interface ID is not a hash of just the MAC address, it's also a hash of the network prefix and a secret that's specific to your system. Including the prefix ensures that the interface ID changes completely when you move to a different network, preventing you from being tracked all over the world. Including a secret ensures that someone can't build a lookup table from MAC address||prefix to stable privacy interface ID. So it's quite superior to using just the MAC address.
      - cm2187 12y ago
        Not really, how many networks do you use in a week. Perhaps 3 or 4. And with this, once a link has been established between the IP, it becomes a permanent static link. It is trivial for advertisers through browser cookies to establish this link, and they only need to do it once.
        agwa 12y ago

by mgbmtl 12y ago

rjsw 12y ago

A house could have multiple users, mine doesn't. I would maybe see turning on privacy addresses as part of a general "leaving home" script that also turned on other stuff like the firewall.

RRRA 12y ago
Time to participate in open wifi or a mesh network :-)
ay 12y ago
You are completely right. Privacy IPv6 address are an illusion when used in a household that has effectively an active /64 per subscriber. (Those who say "but IPv4..." last time my IPv4 address changed, was half a year ago). Anyway this is mostly a political give-in, that happens to also help ruggedize the rest of the stack (the relatively rapid change of privacy addresses uncovers more bugs than we'd otherwise find - so from that standpoint they're to be advocated). But privacy.. huh. Last IETF there was precisely this discussion that one might want to force a new /64 on themselves, and privacy addresses have nothing to do with that. (DHC WG, FWIW).
- X-Istence 12y ago
  Comcast is more than willing to send you more than one /64 prefix if you ask for it!
  - ay 12y ago
    "effectively an active /64". Comcast folks did a ton of testing with the CPEs, and very very few could ask for anything than an active /64, that's why this qualifier :-) There's active (and pretty cool) work in the HomeNet IETF workgroup, with running code and all (http://www.homewrt.org/doku.php http://www.homewrt.org/doku.php) to make the multi-subnet home network a sane reality. But a different /64 from within the same /56 helps not much, and indeed to correctly reflect the spirit of the discussion in the DHC working group, would be to say "I want to be able to press a button and release my currently used allocation and get some completely new one, be it /48, /56 or whatever". Thanks for the correction!
agwa 12y ago
The proper solution is Stable Privacy addresses, recently standardized in RFC7217 [1]. The interface ID is essentially hash(secret || prefix || mac-address), so it stays the same when you're on the same network, but changes as soon as you go somewhere else. [1] https://tools.ietf.org/html/rfc7217 https://tools.ietf.org/html/rfc7217
- cm2187 12y ago
  But that defeats the purpose of a privacy address. The idea is precisely not to use your address as a way to track individual users, like a cookie tattooed on your skin. I fail to see how a hash of the MAC address is better than the MAC address itself.
  - agwa 12y ago
    Because even with traditional privacy addresses, the first 64 bits of your address never change, and you can be tracked that way. If you happen to share those first 64 bits with many other people, then privacy addresses provide value, but that's simply not the case on your home network. Now keep in mind that a stable privacy interface ID is not a hash of just the MAC address, it's also a hash of the network prefix and a secret that's specific to your system. Including the prefix ensures that the interface ID changes completely when you move to a different network, preventing you from being tracked all over the world. Including a secret ensures that someone can't build a lookup table from MAC address||prefix to stable privacy interface ID. So it's quite superior to using just the MAC address.
    - cm2187 12y ago
      Not really, how many networks do you use in a week. Perhaps 3 or 4. And with this, once a link has been established between the IP, it becomes a permanent static link. It is trivial for advertisers through browser cookies to establish this link, and they only need to do it once.
      - agwa 12y ago