What is Signal? Is it a secure service?

Signal has long been known among privacy advocates as one of the most secure messaging apps in the world, thanks to its powerful encryption technology and independent, nonprofit status. But recent revelations about its use by White House officials to discuss military operations have raised new questions about its role—and its limits—in high-stakes environments.

End-to-end encryption and privacy-first design

Signal uses end-to-end encryption that ensures only the sender and recipient can read a message. Not even Signal itself, internet providers, or hackers can intercept and decipher the content. Unlike WhatsApp or iMessage, Signal doesn’t collect metadata like message timestamps or recipient info, offering a more private alternative for users concerned about surveillance.

The app’s development is overseen by the Signal Foundation, not a tech giant. This nonprofit backing, along with financial support from grants and donations, allows Signal to operate without being driven by advertising or data collection, reinforcing its reputation as a trusted privacy tool.

Why experts warn about its limits

Despite its robust encryption, cybersecurity experts warn that Signal was never intended for use in sensitive military communications. Former White House cybersecurity coordinator Michael Daniel emphasized that the main risk lies not in the app, but in the surrounding environment—like personal device security and unauthorized access.

Additionally, the Pentagon recently flagged potential concerns with Signal’s linked device feature, which can open up vulnerabilities if misused by state-sponsored hackers, such as those from Russia.

Ultimately, Signal remains a top choice for secure messaging, but as its use spreads beyond journalists and activists into government circles, experts caution against assuming consumer apps are suitable for national security matters.