Messaging Security Criteria

Not all "encrypted" messaging apps provide the same level of security. Key criteria:

End-to-End Encryption (E2EE): Messages encrypted on sender's device, decrypted on recipient's device. The server never sees plaintext.

Forward Secrecy: If a key is compromised, past messages remain secure. Each session uses temporary keys.

Open Source: The code can be independently audited for vulnerabilities and backdoors.

Metadata Protection: Who you talk to, when, and how often may be as revealing as the content itself.

Data Collection: What information does the service collect beyond message content?

Jurisdiction: Where the company is headquartered affects government access to data.

App Comparison

Signal ⭐⭐⭐⭐⭐ • E2EE: Yes (Signal Protocol) • Forward Secrecy: Yes • Open Source: Yes (client and server) • Metadata: Minimal (sender, recipient, timestamps not stored) • Data Collection: Phone number only • Verdict: The gold standard for secure messaging

WhatsApp ⭐⭐⭐ • E2EE: Yes (Signal Protocol) • Forward Secrecy: Yes • Open Source: No (client only partially) • Metadata: Extensive (contacts, groups, usage patterns shared with Meta) • Data Collection: Phone number, contacts, location, device info • Verdict: Good encryption, concerning metadata practices

Telegram ⭐⭐ • E2EE: Only in "Secret Chats" (not default) • Forward Secrecy: In Secret Chats only • Open Source: Client only (custom MTProto protocol, less scrutinized) • Metadata: Moderate collection • Data Collection: Phone number, contacts, IP address • Verdict: Not a secure messenger by default; cloud chats are server-side encrypted only

iMessage ⭐⭐⭐⭐ • E2EE: Yes (between Apple devices) • Forward Secrecy: Yes • Open Source: No • Metadata: Apple retains some metadata • Data Collection: Apple ID, contacts • Verdict: Strong security within Apple ecosystem, not cross-platform

Recommendations

For most people: Signal for sensitive conversations, iMessage/WhatsApp for everyday messaging with awareness of metadata implications.

For journalists/activists: Signal exclusively. Combine with disappearing messages for additional protection.

For recovery material: Do not assume a disappearing message erases every copy. For Private mode, use an independent custody route appropriate to the threat model and test that the intended recipient can retrieve it.

For group communication: Signal for sensitive groups. Telegram for large public groups where E2EE isn't the primary concern.