Security Indicators

Encryption Status Indicator

The iOS app displays a lock or encryption status indicator in the conversation header. This indicator confirms that the conversation is using end-to-end encryption via the Signal Protocol.

What it means: The indicator shows that all messages are encrypted on your device before transmission and decrypted only on the recipient’s device. The server holds encrypted data only and cannot read the content.

If the Indicator is Absent or Shows a Warning

If the encryption indicator is missing or displays a warning state, do not send sensitive content in that conversation. Contact your administrator immediately. They can verify your device registration and restore the encrypted session.

Session Keys

Each conversation uses session keys unique to that device pair. These keys are derived from the X3DH key agreement protocol during the initial handshake between your device and the recipient’s device. The keys never leave your device and are stored securely in local storage.

For technical details on the cryptographic protocol and key derivation, see the Security section.

Device Registration

Your device’s identity key was generated when you first registered Semafore. This key never leaves your device and is used to establish secure sessions with other members. Your administrator verified and approved your device registration as a security step. Only registered and approved devices can send and receive encrypted messages.