Signal’s planned registration without a phone number will use zero-knowledge proofs (ZKPs), allowing users to prove they meet requirements without revealing the underlying details. The approach can also verify username character sets and lengths without disclosing the username itself.

Signal’s server model is designed to require little client trust, so its safety can be assessed without reviewing server code. Supporters say ZKPs prevent linking users to specific groups or donations, while commenters raised privacy questions about whether phone numbers could be fully separated from usernames and what data might remain on devices or servers.

Some users asked whether existing phone-number registrations can later be unlinked. Others warned that unlimited unlinking could let spammers reuse one number and create unlimited accounts. A cooldown was suggested, though commenters questioned whether it could be long enough to stop abuse without hurting legitimate users.

The discussion remains focused on Signal’s technical details and how the service will balance privacy, account unlinking, and spam prevention.