ProtonMail and Anonymity

[Stefan Claas]

Am Sun, 5 May 2019 14:32:20 -0400
schrieb Jeff Allen <jrallen at runbox.com>:

> On 5/5/19 1:36 PM, Stefan Claas wrote:
> > On Sun, 5 May 2019 11:22:56 -0400
> > Tony Lane <codeguro at gmail.com> wrote:
> >   
> >> Isn't it obvious?  
> > 
> > I don't think so! Users new to privacy related
> > services may think when visiting the ProtonMail
> > site that they are anonymous, when seeing their
> > main page:
> > 
> > https://protonmail.com/
> >   
> 
> I suppose like anything else it all comes down to whether you believe
> them or not.  I do.

[snip]

Well, I just asked myself ...

What is the purpose behind an unlinked hash. 

A spammer using their system, without a hash function
could send successfully spam to other users, because
ProtonMail is not blacklisted. When that happens a
user receiving this spam can report that, so that
actions can be taken. This of course requires then
a bit of work, at the ProtonMail site, to remove
the spammers account.

Why do they use unlinked hashes? If I could sign up
anonymously the hash could also be linked to my account
and even if thousands of people have the same hash they
could remove the spammers account.

Should an unlinked hash protect users from a powerful
adversary? O.k. people can now laugh at me, because
I am no programmer nor cryptographer or math-geek. My
assumption is that a powerful adversary has a list of
all global mobile phone numbers, computes quickle the
hashes for them and saves them also in a database.

How long does it take to find in a database the correct
hash for a given number ...

Regards
Stefan