When selecting messaging apps for sensitive activities, evaluate them based on these security properties:
End-to-End Encryption (E2EE)
Ensures only the sender and recipient can decrypt communications. When evaluating providers, check if:
- Metadata is protected or just the content.
- E2EE is opt-in (disabled by default) or opt-out.
- E2EE applies to group messaging as well as 1-to-1.
- The app is Open-Source, allowing verification of encryption claims.
Forward Secrecy (FS/PFS)
Ensures that every new session generates a new set of keys. If current keys are compromised, past communications remain secure. Prefer open-source apps that implement this, as some providers omit it for usability (e.g., in group chats).
Zero-Access Encryption at Rest
Ensures that data stored by a provider (like chat history or backups) is encrypted on your side, so the provider cannot read it. This protects against server-side hacks and data harvesting.
Metadata Protection
E2EE protects content, but not necessarily metadata (who you talk to, when, for how long, group memberships). Look for protocols like the Signal Protocol which offers features like:
- Sealed Sender
- Private Contact Discovery
- Private Group System