Signal to support phone-number-free registration via ZKP
Original: Registration without a phone number on Signal will use zero-knowledge proofs
Why This Matters
Phone-number-free sign-up removes a key identity anchor that governments and carriers can subpoena.
Signal is actively developing phone-number-free account registration for Android, with multiple commits merged in late August and early September 2026. The feature uses zero-knowledge proofs (ZKP) to verify account credentials without revealing identity, extending the same cryptographic approach already used for groups and donation badges.
Signal's Android repository received a series of commits between August 25 and September 2, 2026, laying out the infrastructure for numberless account registration. Commits include 'Add basic ability to register numberless account,' 'Add basic ability to login to an existing numberless account,' 'Add password manager support to numberless login,' and several supporting changes that hide phone-specific settings—such as PIN reminders and phone number discoverability—for numberless accounts.
The feature relies on zero-knowledge proofs, the same cryptographic mechanism Signal already uses for group membership and donation badges. Signal engineer Alex Hart noted that ZKP is also used to verify username character set and length without exposing the actual content. Community members confirmed that Signal's client-side design already avoids trusting the server, making the architecture consistent with the app's existing privacy guarantees.
Open questions remain: whether existing users can unlink a phone number without re-registering, and exactly what metadata—if any—persists locally or server-side after switching. Some community members suspect full unlinking may not be technically clean, suggesting new numberless accounts might offer stronger privacy than converted ones. No public release date has been announced.