What is Messaging App Signal? All You Need to Know About Its Encryption

Encrypted messaging app Signal is making headlines after it was revealed that senior members of US President Donald Trump's administration were discussing war plans on the platform. A Signal group, which included officials like Vice President JD Vance, Defence Secretary Pete Hegseth, and Secretary of State Marco Antonio Rubio, mistakenly added a journalist from The Atlantic magazine.

The officials were discussing a plan to bomb Houthi-led Yemen in the Red Sea. On March 15, the United States conducted airstrikes in Yemen targeting Houthi rebels. According to The Atlantic journalist’s report, the group discussion allegedly focused on the timing of the attacks and whether economic leverage could be “extracted” from Europe in exchange for the bombings.

Following the report, Democrats have called for the resignation of top-level officials, calling it a "violation of all procedures."

After the incident, senior intelligence officials from the Trump administration, including CIA Director John Ratcliffe and Director of National Intelligence Tulsi Gabbard, were questioned by lawmakers in a hearing on March 25.

“This was not only sloppy. It not only violated all procedures, but if this information had gotten out, American lives could have been lost. If the Houthis had this information, they could reposition their defensive systems,” said Democratic Senator Mark Warner.

Later, President Trump dismissed the issue, saying, "There was no classified information, as I understand it. We’ve pretty much looked into it. It’s pretty simple, to be honest. It’s just something that can happen."

What is Signal?

Launched in 2015, Signal is an online messaging app available on iOS, Android, and desktop. According to Google Play Store, more than 100 million users have downloaded the app. Signal’s key feature is its end-to-end encryption for messaging and calls, which prevents any third party from accessing content.

The app was created by cryptographer Moxie Marlinspike (Matthew Rosenfeld) and roboticist Stuart Anderson in 2010 under Whisper Systems, which developed the encrypted messaging apps TextSecure and RedPhone.

After Twitter (now X) acquired Whisper Systems in 2011, Marlinspike founded Open Whisper Systems in 2013 and launched Signal in 2014, initially for phone calls, later adding messaging in 2015.

In 2018, WhatsApp co-founder Brian Acton invested $50 million to establish the Signal Foundation with Marlinspike. Now, this independent nonprofit foundation owns the app. According to The New York Times, the foundation is structured in a way that prevents Signal from ever having an incentive to sell user data, something many tech firms rely on as a source of income.

Acton became interim CEO when Marlinspike stepped down in 2022 and was confirmed as CEO in 2023.

“There are so many great reasons to be on Signal. Now including the opportunity for the Vice President of the United States of America to randomly add you to a group chat for coordination of sensitive military operations. Don’t sleep on this opportunity,” Marlinspike wrote on X after the Trump administration’s chat leak was exposed.

How Secure is Signal?

"Signal conversations are always end-to-end encrypted, which means that they can only be read or heard by your intended recipients. Privacy isn’t an optional mode—it’s just the way that Signal works. Every message, every call, every time," the platform claims. The complete source code for Signal’s clients and servers is available on GitHub.

The company prioritises user privacy by minimising the storage of user data on its servers. Signal retains only essential information, such as phone numbers, registration dates, and last login times. All messages, contacts, and other communications are stored locally on users’ devices, with options to set automatic deletion after a specified period.

Signal does not rely on advertisements or affiliate marketing and explicitly states that it does not track user data. Additional privacy features include the ability to hide phone numbers from other users and the use of safety numbers to verify message security.

Signal operates independently of government encryption standards and does not host its services on government servers.

"Signal is the gold standard in private communications. WhatsApp licenses Signal’s cryptography to protect message contents for consumer WhatsApp," Signal President Meredith Whittaker said in defence of the app's security on 25 March.

However, it has been reported that Russia-aligned hackers have attempted to target individuals on the app to gain unauthorised access to their accounts.

"The most novel and widely used technique underpinning Russian-aligned attempts to compromise Signal accounts is the abuse of the app’s legitimate 'linked devices' feature, which enables Signal to be used on multiple devices concurrently," the Google Threat Intelligence Group (GTIG) reported on 20 February 2025.

Are US Govt Officials Allowed to Use Signal?

According to US media reports, Department of Defense (DoD) officials are not permitted to communicate on Signal, as it does not comply with the US Freedom of Information Act and the department’s records retention policies.

As for the State Department, the use of Signal is generally "permitted but discouraged," with decisions left to the discretion of individual users based on specific contexts.

However, in 2017, the Senate Sergeant at Arms approved the use of Signal for lawmakers and staff. According to the Associated Press, under the previous Joe Biden administration, officials were authorised to use Signal on White House-issued phones but were advised to use the app sparingly.