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Comment by kbsletten | Hacker News Reader

So, I'm really not trying to start a fight, please read this with curious intent.

I personally don't really feel like keeping my email is a violation of my privacy. If they're not "processing" it (that feels like code for "data mining") is this really required? I mean my email address is literally a public means of contacting me. It's kind of fun that they decided to use a one-way hash, but this story doesn't make me feel like the internet has really been improved.

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The problem is identification of physical persons. Your e-mail is public, but it also identifies you as a person. This is important, because it allows for correlating different data sets.

Touch Surgery sounds like a honest company, so for them this was just some extra burden. But the same law prevents ShadyAdtechCo from getting datasets from several companies and joining them on e-mail column to build a profile of you, without your explicit, informed consent in several places.

Wouldn't then a hash of your email also identify you as a person? The companies can still build a profile of you if they just agree to use the same hashing function :/

Or even if ShadyAdtechCo just knows what the hashing function is, and has a list of plaintext email addresses to test against – perhaps obtained from one of the datasets they're joining against, or even from crawling the web.

Hashing should be done with salt for precisely that reason.

If you mean a static salt, that could help mitigate against hacks (if the attacker has access to the database but not the code), but where adtech is concerned it's probably more realistic to assume that the datasets they're using were disclosed willingly. If you mean using a different salt for each address, that could work for some use cases, but it wouldn't work for the use case described in the blog post, since Touch Surgery needs to be able to lookup whether a given address is in the database (to see whether they've previously declined an invitation).

Why is it reasonable to assume they were disclosed willingly? That sounds like a startling assumption and the reverse of the one I'd make.

Without good evidence, you must assume they were disclosed unwillingly.

It's really no problem to do this. We're using a variation on this: https://unix.stackexchange.com/questions/158400/etc-shadow-h.... The output of crypt (where the input is an email address) is pretty useless if we did suffer a data breach. They'd have to hash every known email address with that salt in order to figure out who had declined an invite from us.

What is the salt based on?

Couldn't the salt be unique to the requesting account? I would assume that just because a user declined an invitation from one user, they still might want to accept an invitation from a separate user.

IANAL, but specifying how you hash the e-mails (algorithm + salt generation) would be part of your GDPR compliance process.

We'll have to wait til someone got sued into oblivion before we know that

Noone will get sued under the GDPR. That's not how it works.

Article 79 says that each data subject that considers that their rights under GDPR have been violated by a controller or processor has the right to an effective judicial remedy, which may be brought before a court in either the Member State where the data subject resides, or where the controller or processor has an establishment.

This is distinct from administrative and non-judicial remedies.

That sure sounds like suing.

An email address identifies an email address, not a person. More than a few times I've signed up to newsletters with a distribution list address, that maps to n number of actual people behind the group, who may or may not be fixed members of that group.

You could track c_sharp_enthusiasts@myCompany.com, but that is not identifying a person.

In many cases it will identify a person. I have two email addresses, a personal one and a home one, and I don't use any others. In my case this absolutely will identify me, and I would argue that in the vast majority of case this will be true as well. You're unusual relative to the general population in using distribution list addresses, and they have to start somewhere. I would also argue that this is exactly the piece of information that is most commonly used to merge datasets, and that's probably why the legislation includes it.

No one but us computer supernerds makes that distinction. On the consumer market, an email address is an excellent way to identify a person over a very, very, very long time. No one but the tech-literate change their email too often.

No idea if deleting the email is required under GDPR, but for a taste of why it might be, imagine scaling up a bit. If they keep one email in this scenario, they're keeping one personal fact: email A is affiliated with email B. Suppose that process runs at scale for a while, and ends up with a database of 10 million email addresses averaging 100 connections. That becomes a digital map of society, with lots of private facts hidden in it -- a valuable/dangerous pile of surveillance to leave lying around for no reason, even if they're not actively using it.

There's a big difference between one fact and a billion, of course. But that's what keeps happening on the internet -- what feels like one small harmless thing turns out not to be harmless at scale, with no real warning that you're crossing from one regime to the other.

> If they're not "processing" it (that feels like code for "data mining") is this really required? I mean my email address is literally a public means of contacting me.

It's also a means of identifying you. It's not just the piece of data, even if it's only your mail address that is stored it can be sensitive information due to context. Say, due to a data breach a list of all members of a company's mailing list is leaked. You might not mind too much if your publicly known mail address shows up on Amazon's mailing list, but you might care if it shows up on the leaked mailinglist of transexual-midget-porn.com

What if someone else registered using his email (some websites for example don't send confirmation email if you change it in your profile or add additional email) or leaked data is fake? How that protects him?

You can't store the e-mail address without consent, and getting consent would probably involve sending a confirmation email.

But providing an email so it can be associated with your profile implies giving consent, as you don't have to do that.

GDPR requires explicit consent if you're using consent as your legal basis for storing that contact email.

Keeping your email without a use case is a violation of your privacy.

How would you feel if you had to give your home address to the baker to buy a pastry?

I see what you're saying, but I also feel like the two are very different to me.

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