Having signal be tethered to a real phone number does give you a point to root your account around, and allow recovery. It must reduce spam, and it's always a way to find other users. But I do find it irritating that you can't have a virtual account too. When my phone busted, because I hadn't saved off all my security recovery info, it didn't matter that I had signal running on my laptop, etc, I had to reset my signal account on my new phone. It would have been nice if I could have "added" a new root account on my new phone from a working device. keybase allowed this.

It is borderline trivial to steal someone else's phone number through social engineering and the systems underlying the world's GSM networks are very easy to spoof, MITM, and otherwise hijack with a minimum of equipment.

It's crazy to me that with all of Signal's emphasis on security (being designed by one of the top security researchers in the world, no less), they chose to make tying your account to a phone number a requirement.

I go very far out of my way to make sure that nothing important to me is tied to my phone number.

If you have and use Signal you can tell it not to let somebody else hijack Signal along with your phone number. You set a PIN, and then it pesters you for the PIN periodically to check you didn't go "Oh I'll just type some random digits and then moan later when I'm locked out, that'll be fine".

So long as you keep entering the correct PIN periodically, Signal won't let anybody register with your phone number without knowing the PIN you've shown you remember.

If you quit using Signal, after a while there haven't been any correct PIN entries for too long and anyone can claim that phone number again (and if they want, set a new PIN).

Anecdata: just set my mom's new iPhone up today, and re-registering Signal required she set up the registration lock PIN. I don't personally use that feature yet but interesting that it was mandatory.

That introduces the problem of someone getting a new phone number. If the previous user had it tied to pin+signal it means that the number is essentially blacklisted.

If you get a new phone number the week after a prolific phone user lost it, I'm guessing that would be super annoying already?

"Hello? No, this isn't Dave, he got a different number. No I don't know what it is. No this isn't a prank, please stop calling"

As a result I would imagine that unless the network is absolutely clean out of numbers (which they try hard to avoid) it will just never reuse numbers in such a short period. The only way somebody else has the number while the PIN is valid is that they're attacking you, which a PIN blocks.

So my guess would be that this ends up not being a problem in reality, it worried me right up until I read the expiry mechanism and then I went oh, that makes sense.

Ha! True. Well, a less prolific number may not get all the calls.

I've seen first hand how numbers can be reused fairly quickly (months). (This was in the Caribbean).

A 7 day pin expiry? I need to look at more details here because I can definitely go 7 days without using my phone. Or, I've travelled abroad and used a local SIM while my "home sim" was never in use for the duration of the stay. (But I kept the ID number on whatsapp/signal/telegram).

The PIN lock expires after 7 days unless you re-auth, so this is only a temporary inconvenience.

> It's crazy to me that with all of Signal's emphasis on security (being designed by one of the top security researchers in the world, no less), they chose to make tying your account to a phone number a requirement.

It isn't crazy. There's a tradeoff between convenience and security. Signal appears to trying to create the most secure system that's still usable by most people, and are advancing the state of the art in many areas to make that happen.

It's important to keep in mind that the best security in the world is of no use if you don't bother to use it.

In any case, Signal gives you optional actions you can take to solve some of the problems your concerned with.

> Having signal be tethered to a real phone number does give you a point to root your account around, and allow recovery.

It also makes it dead simple for most users, even nontechnical ones, to use and understand. They don't even have to do anything special, their Signal contact list is already bootstrapped when they install the app.