If you join a large WhatsApp group, anyone in that group will have everyone else's phone number, and they can use that to learn far more about everyone's identities.

Does it not give away your identity when you join a Signal group?

I haven't used the groups, but I know you CAN opt to use usernames now.

settings > privacy > phone number > who can see my number > nobody

Signal defaults to hiding your phone number since the release of user names: https://signal.org/blog/phone-number-privacy-usernames/

Not worried about my phone number so much as my legal name...

Not worried about my phone number, I'm more worried about my profile.

For those that want more security:

SimpleX Chat: private and secure messenger without any user IDs (not even random)

SimpleX Chat - a private and encrypted messenger without any user IDs (not even random ones)! Make a private connection via link / QR code to send messages and make calls.

(simplex.chat)

Maybe I'm just weird, but basically nothing I do in an online capacity traces back to my IRL identity. (I do maintain a linked in for professional purposes.)

No requirement to have your legal name in Signal. Though, I do wish it was possible to set a different name for group chats though. Happy to use my real name with friends and family, but would prefer an alias for group chats.

Your profile, like everything else on Signal, is also end-to-end encrypted. Your name and profile picture do get shared with whoever you chat with, groups or individuals. If you don't want your name and profile picture shared with randos, either don't set them or don't chat with randos.

Let's stay in touch! I'm on Signal. Just text me on Telegram. I've got Whatsapp with ads. I'm literally on Snapchat. You can probably find me on Kik. Dude text me on Matrix. It's a Wechat feature. I'm on Simplex. You can text me on Simplex. You can go to Simplex and text me. Log onto Simplex right now. Go to Simplex. Dive into Simplex. You can Simplex me. I'm on Simplex. Simplex has it for you. Simplex has it for you.

Happy to use my real name with friends and family, but would prefer an alias for group chats.

Exactly.

your profile...is also end-to-end encrypted

That's fine if one of those ends isn't a public activism group.

If you don't want your name and profile picture shared with randos, either don't set them

I use Signal to talk to people I actually know, both personally and professionally. I don't want to message them from some sort of unidentifiable alias. And if I did they would know my alias and could disclose it to law enforcement.

or don't chat with randos.

You mean randos like you might find in a public activism group chat? Yes, that was my point, thank you.

Simplex does not give you anymore security. It does however, provide anonymity.

Signal, yes...

Or snikket (xmpp).

Or delta chat (email).

The three are good.

But they must still have your phone number and associate it with your username. So it would still be easy for a government organization to force Signal to give up the identities of all people who join a group.

Simple-X ?
GNU-Jami ?

what's the security issue about simplex??

Wrong. Signal servers don't know of group members.