> one can totally implement NAT for IPv6, and in fact people have
Please don't say things like this out loud!
The purpose of IPv6 was to eliminate the need for filthy hacks like NAT.
NAT does nothing for privacy, not in theory, not in practice.
Everyone trying to get at your private information has figured out hundreds and hundreds of methods for tracking you. Single pixel images. Browser fingerprinting. Hardware fingerprinting. Mouse movement patterns. You name it, they're doing it.
They're not at all slowed down by NAT, but the Internet is harmed by it.
I think the situation is quite a bit more complicated than you make out.
To my ISP, NAT obscures device browsing history (assuming there are multiple people and devices within a household). To the best of my knowledge an ISP has no realistic way of engaging in mass browser fingerprinting.
To a web host, NAT obscures the number of users behind a given IP address. Sure, they can likely recover some amount of information by engaging in browser fingerprinting but right off the bat it makes their job harder.
Security and privacy both involve layers. Every bit of information leaked is a concession to an adversary. When I switch my home network over to IPv6 I will almost certainly add NAT to it.
> the Internet is harmed by it
I don't believe you. Shitty software is harmed by it. If you have concrete examples to the contrary, I'm open to them.
> To my ISP, NAT obscures device browsing history (assuming there are multiple people and devices within a household). To the best of my knowledge an ISP has no realistic way of engaging in mass browser fingerprinting.
There's plenty of information that an ISP could silently listen in on, e.g. user-agent header, pre-STARTTLS cipher suites. And realistically how many people are there in a household, and how much do they reflect on each other? What's the threat model where this is a realistic improvement in your privacy?
> Sure, they can likely recover some amount of information by engaging in browser fingerprinting but right off the bat it makes their job harder.
> Security and privacy both involve layers. Every bit of information leaked is a concession to an adversary.
Weak privacy measures are worse than nothing just like weak security measures. Putting in effort to obscure one or two bits is a false economy. One solid layer (e.g. Tor) will protect you far better than any number of weak layers.
> I don't believe you. Shitty software is harmed by it. If you have concrete examples to the contrary, I'm open to them.
Everything peer-to-peer is made needlessly harder, and the result is centralisation that hurts the overall internet. E.g. in a non-NAT world, hosting a multiplayer game and letting your friends join is easy; with NAT, it's hard enough that people rely on the manufacturer providing servers (which they won't do indefinitely) instead.
I thought temporary addresses were supposed to (mostly) solve this and would be my preferred way. Though the default 24h lifetime is not quite as helpful, except for hopefully sidestepping the genius - embedded by MAC into my IPv6 - address generation.
It's in a nearby comment chain, but apparently my understanding was outdated and/or just incomplete. The SLAAC privacy extensions will make use of a full /64 prefix instead of a device specific one. That makes it functionally equivalent to NAT if and only if addresses are rotated on a very frequent (ex per browser tab) basis. (I wonder if you could rotate per origin within the same tab?)
You do realise that most IPv6 implementations randomise the /64 "host" part of the address, right?
IPv4 NAT does not provide any additional privacy over IPv6.
You can jump up and down and claim the contrary, but it's just not the case.
Meanwhile, Facebook, Google, and the like are scraping petabytes of information about every Internet-connected person on the planet and selling it to the highest bidder. These organisations are not slowed down in the slightest by IPv4 or IPv6.
Please don't say things like this out loud!
The purpose of IPv6 was to eliminate the need for filthy hacks like NAT.
NAT does nothing for privacy, not in theory, not in practice.
Everyone trying to get at your private information has figured out hundreds and hundreds of methods for tracking you. Single pixel images. Browser fingerprinting. Hardware fingerprinting. Mouse movement patterns. You name it, they're doing it.
They're not at all slowed down by NAT, but the Internet is harmed by it.
Stop giving advice like this.