Choosing an encrypted messaging app: 6 questions before you install

• 1. Does it need your phone number?
• 2. Is the encryption end-to-end by default?
• 3. Who runs the servers, and under which law?
• 4. What metadata is kept?
• 5. Personal or team use?
• 6. The phone matters as much as the app

Most people pick a messenger because their friends are already on it. That’s fine for group chats about dinner. It’s less fine if your messages carry client details, sources or travel plans you’d rather keep to yourself.

Here’s the short checklist we use at Ghost SIMs when someone asks which encrypted messaging app to put on a privacy phone.

§1. Does it need your phone number?

A phone number is an identity. It ties your account to a SIM, and usually to a name at a carrier. Signal is excellent cryptographically, but registration still needs a number (you can hide it behind a username now, the number still exists on the account). Threema lets you sign up with a random Threema ID and no number or email at all. If keeping your identity off the account matters, start there.

§2. Is the encryption end-to-end by default?

“Encrypted” on a feature list can mean encrypted in transit to the company’s servers, which isn’t the same thing. You want end-to-end encryption switched on for every chat and call by default, not a “secret chat” mode you have to remember to open.

§3. Who runs the servers, and under which law?

Swiss-hosted Threema, enterprise suites you can self-host, and US-based services all carry different legal exposure. None of that breaks good end-to-end encryption, but it does decide who can be asked for metadata like who talked to whom and when.

§4. What metadata is kept?

Message content is only half the picture. Contact lists, timestamps and IP addresses tell a lot of the story. Look for apps that minimise contact discovery and say clearly what they log.

§5. Personal or team use?

For a handful of people, a consumer app is enough. For a company, you’ll want admin controls, device management and a way to remove leavers. That’s where options like Threema Work or VNClagoon come in.

§6. The phone matters as much as the app

An encrypted app on a phone full of trackers is still leaking. Pairing it with a hardened OS such as GrapheneOS, and a SIM that isn’t tied to your name, closes most of the gaps the app can’t fix on its own.

We list the apps we set people up with (Threema, Threema Work, Armadillo, Silent Circle, VNClagoon and VaultChat) on our encrypted messaging apps page: encrypted messaging apps at Ghost SIMs.

Disclosure: this is written by the Ghost SIMs team, and we sell licences for the apps above.