[beeb]

At least for Plausible, they state this (https://plausible.io/blog/google-analytics-cookies):

> Instead of tagging users with cookies, we count the number of unique IP addresses that accessed your website. Counting IP addresses is an old-school method that was used before the modern age of JavaScript snippets and tracking cookies.

Since IP addresses are considered personal data under GDPR, we anonymize them using a one-way cryptographic hash function. This generates a random string of letters and numbers that is used to calculate unique visitor numbers for the day. Old salts are deleted to avoid the possibility of linking visitor information from one day to the next. We never store IP addresses in our database or logs.

[chrismorgan]

> Since IP addresses are considered personal data under GDPR, we anonymize them using a one-way cryptographic hash function.

Um... hashing IPv4 addresses, even with salt, does literally nothing to anonymise (assuming the output space is at least ~32 bits, which I think is safe to assume): they’ll still be PII. IPv6 addresses I’m not so confident about; maybe it would be sufficient for some parts, but it’s definitely inadequate for some concerns.

(For IPv4, enumerating all four billion inputs is so completely practical that “one-way” is nonsense.)

I’m almost certain this is legal theatre.

[Semaphor]

One way if you have a salt? Enumerating won’t help, you need to know the salt, which gets deleted.

That said, the whole IP thing is weird to me. Not only are we allowed to log IPs directly for security reasons, we even *have* to log IPs in certain cases (newsletter subscriptions).

[alkonaut]

Couldn't this be done with a Bloom filter in such a way that (in exchange for a small error rate) you'd not keep any individual hashes?

[kadoban]

If what they're doing is using a secure salt and then throwing the salt away once a day that _might_ be doing something.

[jszymborski]

What matomo does is mask parts of the IP address (you choose how much).

[gizzlon]

hm.. are you saying they need scrypt or something similar?