In May, according to App Annie, the encrypted messaging app Signal was downloaded one million times worldwide, a result of both the COVID-19 pandemic and the more recent protests over George Floyd’s death and police brutality. Sensor Tower reports that Signal currently has 32.4 million installs. Privacy advocates have always been attracted to Signal’s ability to limit the information it can give to authorities. Signal’s end-to-end encryption is considered more secure than what is offered by Facebook’s WhatsApp and Apple’s iMessage.

The Wall Street Journal reports that Signal offers privacy features such as not logging much metadata about messages and requiring the user to activate video when he picks up a call. “Signal makes it a point to keep as little data as possible while still being able to provide service,” said Carnegie Mellon University professor of computer science Lujo Bauer.

App creator Moxie Marlinspike stated that, “the only data the U.S. government was able to obtain from a 2016 grand jury subpoena was the date of an account’s creation and the date of last use, nothing else.” Both WhatsApp and iMessage retain some information and provide it to authorities if presented with a “valid legal request.”

“Just knowing who the contacts of a target are can expand an investigation,” said University of Washington law professor Mary Fan.

WSJ notes that, “cloud backups, while convenient, are yet another potential vulnerability with popular apps … [since] media and messages stored in the cloud aren’t protected by end-to-end encryption on either WhatsApp or iMessage.” Meanwhile, “all Signal data is stored locally,” and Signal itself is “backed by a nonprofit foundation — with $50 million from WhatsApp co-founder and Facebook ex-executive Brian Acton.”

Signal is barebones compared to WhatsApp and iMessage, and both WhatsApp, with two billion users, and iMessage, with almost two billion iPhones, have huge install bases compared to Signal.

The New York Times reports that Signal downloads skyrocketed in the last two weeks, with many “using the app to organize and participate in protests against police brutality (without being spied on by law enforcement).” Sensor Tower reported that, “the week before George Floyd died on May 25, about 51,000 first-time users downloaded Signal …  the following week, as protests grew nationwide, there were 78,000 new downloads” and, “in the first week of June, there were 183,000.”

Protest organizers use Signal for operations and strategies, and individual protesters use it to stay in touch with friends. “If you don’t have end-to-end encryption, by definition, there are other parties that can read your messages,” said New York University assistant professor of computer science Joseph Bonneau. Signal lets users “set their messages to delete after a period of time” and also “introduced a ‘blur’ tool for photographs,” which could aid protesters.