Threema¶

Best suited for: Peer-facing pseudonymity without a mandatory number. [1] [2] [3] [4]
Avoid if…: You require PFS on Desktop 2.0 beta or network anonymity. [1] [2] [3] [4]
Main strength: ID without mandatory phone or email; mobile maturity. [1] [2]
Main weakness: Desktop beta limits, account data and linkable purchases. [1] [2]
Account identifier: Random Threema ID; optional phone and email. [1] [2]
iOS: Yes, client listed in the study. [1] [2]
Android: Yes, client listed in the study. [1]
Windows: Beta; desktop-specific limits. [1] [2]
macOS: Beta; desktop-specific limits. [1] [2]
Linux: Beta; desktop-specific limits. [1] [2]
Confidence and scope: Client-specific properties; no PFS in Desktop 2.0 beta, retest status needs verification. [1] [2]

What your contact learns¶

What the contact learns: The contact receives messages and the profile you share, and can keep a copy. [1] [2]

What the provider learns: ID and connection data; aggregate account-data disclosures are published. [1] [2]

What the network / ISP learns: The network sees destinations, timing and volume; Tor or a relay changes the observer. [1] [2]
Apple / Google exposure: Store, installation and push can create metadata; exact profile linkage depends on the OS and was not tested here. [1] [2]
Public law-enforcement evidence: 2025 and H1 2026 reports: aggregate account-data disclosures; not evidence of message-content disclosure. [1] [2] [3]

E2EE: E2EE; properties depend on the client, particularly desktop beta. [1] [2]
Forward secrecy: Desktop 2.0 beta does not support PFS; do not generalise to other clients. [1] [2]
Post-compromise security: Unknown: not established for the version and configuration in question.
Key verification: Verify identity / fingerprint through a separate channel. [1] [2]

Metadata exposure: ID, connection data and optional identifiers; store purchase may link identities. [1] [2]
Global user ID: Persistent random ID; optional linked identifiers add correlation. [1] [2]
Username / discovery: Unknown: not established for the version and configuration in question.
Push notifications: Unknown: not established for the version and configuration in question.

IP exposure to peer: Check calling mode and relay per client and configuration. [1] [2]
Relay / TURN: Call relay properties must be checked on the client being used. [1] [2]
Calls: Unknown: not established for the version and configuration in question.
Groups: Unknown: not established for the version and configuration in question.

Multi-device: Desktop 2.0 beta: up to two computers, no PFS; older client depends on the phone. [1] [2]
Backups: Unknown: not established for the version and configuration in question.

Audits: Cure53 and Ibex analyses: distinct scopes; desktop retest status needs verification. [1] [2] [3]
Source code and binaries: Repositories and component-specific scopes recorded in Phase 2; no current binary rebuilt bit-for-bit here. [1] [2]
Main weakness: Desktop beta limits, account data and linkable purchases. [1] [2]
Public law-enforcement evidence: 2025 and H1 2026 reports: aggregate account-data disclosures; not evidence of message-content disclosure. [1] [2] [3]

Recommended configuration: Do not link phone or email without need; verify fingerprints and each client’s limits. [1] [2] [3] [4]
Remaining unknowns: Current network behaviour, distributed binaries and forensic evidence remain incomplete; check version, OS and configuration. [1] [2]

End-to-end encryption — E2EE

Participants’ devices control content keys. The transport server should not read ordinary messages. Learn more

Metadata

Data around the exchange: accounts, IP, timing, volume, devices or groups. Learn more

Pseudonymity

Use an identity different from your civil identity. It can still be linked to you. Learn more

Network anonymity

Reduce the ability to link traffic to your network address or its destination. Learn more

The detailed evidence is maintained in the French Phase 2 register. The translation is a restatement, not new evidence.