There is a setting in Signal to alert you when one of your contacts joins Signal. Only other people who have Signal receive this notification and they can turn it off.
They also don't receive the alert because they were in your contacts. They receive the alert because you were in their contacts.
It preserves the privacy of your contacts (no one learns that you have them as a contact) and people have a choice about whether to receive the notifications (it isn't spam). That's not worse.
> Is there a setting when you join that doesn't blast it to everyone who has you as a contact?
It isn't blasting it whatsoever. Their client is querying whether any of their contacts has Signal. If one does now that didn't before, and their client is configured to notify them when that happens, their client notifies them when that happens.
The client has to be able to determine whether it can use the network to contact a given peer. Removing the ability to provide a notification when that happens is just security through obscurity.
It's not clear to me what you're actually asking for.
Signal, like it or not (I feel both ways) is keyed on phone numbers. When you look for someone, that's what you look for, and unless someone messages you first, you have to look for them.
So anyone who has your phone number and thinks "hmm, is so and so on Signal?" will find out, yes.
What's the downside to them opting in to getting alerts that the answer is now yes? I find them annoying and turn it off, but I can't avoid anyone who has my number messaging me one time on Signal, that's just how the platform works.
> So anyone who has your phone number and thinks "hmm, is so and so on Signal?" will find out, yes.
It would be more privacy preserving to prevent that user from ever knowing the answer until I send them a message.
The usual areas this is a problem are for example: bad exes, poor former business relations, anyone who is harassing/stalking someone, and so on. I enjoy Signal as an app but it's a bit disingenuous to pretend that there aren't other ways of architecting a messenger system that could preserve anonymity better.
> It would be more privacy preserving to prevent that user from ever knowing the answer until I send them a message.
Someone has to send the first message. To have end to end encryption, that someone needs to be able to retrieve the other person's public key in order to be able to send it. This means they can determine whether you have a public key, i.e. whether you have the app.
> The usual areas this is a problem are for example: bad exes, poor former business relations, anyone who is harassing/stalking someone, and so on.
If your bad exes don't have your phone number, they don't learn that you installed Signal. If they do have your phone number, they learn that you installed Signal, but if them learning this one bit of information is an actual problem for you, maybe you should change your phone number.
There is a setting in Signal to alert you when one of your contacts joins Signal. Only other people who have Signal receive this notification and they can turn it off.
They also don't receive the alert because they were in your contacts. They receive the alert because you were in their contacts.