Signal Sealed Sender: Can Recipients See Who Sent?

TL;DR

No, a data requester cannot directly identify the sender when Signal’s Sealed Sender feature is enabled. Sealed Sender adds an extra layer of privacy by preventing even Signal servers from knowing who sent a message. However, metadata like timing and group membership can still potentially reveal information.

Understanding Sealed Sender

Sealed Sender uses cryptographic techniques to hide the sender’s identity from Signal’s servers. Normally, when you send a message, Signal knows which user account sent it. With Sealed Sender turned on, this link is broken. Only the recipient can decrypt and see who actually sent the message.

Can Data Requesters See the Sender?

Data requesters (like law enforcement with a warrant) typically ask Signal for information about users and their communications. Here’s what they can and cannot get when Sealed Sender is in use:

Steps to Understand Data Access Limitations

1. What data *is* accessible: A data requester can access metadata such as:
   • When the message was sent/received (timestamps).
   • Who the recipient is.
   • If the communication occurred within a group chat, who the other members are.
   • Device information associated with accounts (if registered).
2. What data *is not* accessible: The identity of the sender is hidden from Signal’s servers and therefore unavailable to data requesters.
   • Signal does not store a record linking the message content to a specific sender when Sealed Sender is active.
   • The recipient’s device decrypts the message locally, meaning Signal never knows who sent it.
3. How data requesters might try to infer identity: Even without direct access to sender information, a requester could attempt to correlate metadata:
   • Timing analysis: If the requester knows when you typically communicate with someone and has access to message timestamps, they might make an educated guess.
   • Group chat analysis: If you’re in a small group chat, knowing who else is communicating around the same time could narrow down possibilities.
   • Account registration information: If your phone number or email address is linked to your Signal account and compromised elsewhere, it could be used to identify you.

Practical Steps for Enhanced Privacy

1. Enable Sealed Sender: Make sure Sealed Sender is enabled in your Signal settings (Settings > Privacy > Sealed Sender).
2. Be mindful of group chats: Smaller groups are easier to deanonymize. Consider the privacy implications before joining or participating in them.
3. Protect your registration information: Use a burner phone number or email address if possible, and keep your account details secure.
4. Regularly update Signal: Updates often include security improvements that can further protect your privacy.

   # No specific command needed - ensure you have the latest Signal app version

Important Considerations

While Sealed Sender significantly improves privacy, it’s not foolproof. Metadata remains a potential source of information for determined data requesters. Combining Sealed Sender with other privacy practices (like using a VPN and being cautious about sharing personal information) provides the best protection.