According to British press reports, the assailant involved in last week's London terror attack that left three pedestrians and one police officer dead — and dozens more wounded — used WhatsApp just minutes before the rampage.
But because the messages sent by and to attacker Khalid Masood are encrypted by the popular messaging app, officials are unable to access them.
"We need to make sure that organizations like WhatsApp — and there are plenty of others like that — don't provide a secret place for terrorists to communicate with each other," Britain's Home Secretary Amber Rudd said in multiple interviews Sunday.
Whether you use the app or not, here are some things to know about WhatsApp and the encryption debate:
What is WhatsApp?
WhatsApp is a popular messaging app with end-to-end encrypted instant messaging that can be used on various platforms, including Android, iPhone and Windows smartphones, and Mac or Windows PCs.
Created in 2009 and later acquired by Facebook in 2014, the app uses your phone's internet connection to send messages so you can avoid texting fees.
What can you do with the app?
In addition to making calls, sending messages, photos, videos, files and voice messages to individuals or groups, WhatsApp rolled out some new features in 2017.
Now, the app includes a Snapchat story-like feature, which allows users to update their “status” using pictures, GIFs and videos.
You can also swipe up to reply to your friends’ statuses.
Who uses it?
According to Facebook’s earnings call on Feb 2, 2017, WhatsApp had 1.2 billion monthly active users, Statista reported.
The popular messaging app is used by people in more than 180 countries around the world.
What is end-to-end encryption?
End-to-end encryption is a security system in which only the sender and the recipient can read their own messages. In fact, even WhatsApp can’t access user messages.
Apple’s iMessage also uses end-to-end encryption.
What is the debate around ending end-to-end encryption?
Following the London terror attack, Home Secretary Amber Rudd called for WhatsApp and other encrypted services to offer a "back door" system for officials, AP reported.
In 2015, following the San Bernardino, California shooting that left 14 dead, the FBI requested Apple for the passcodes needed to unlock an iPhone used by one of the perpetrators.
But Apple and other tech industry giants, as well as privacy advocates, say creating security loopholes would be dangerous as it opens the door to cybercriminals, too.
While tech companies should help officials when possible, the help should be requested through warrants where the process is both properly regulated and monitored, Jim Killock, executive director of Open Rights Group, told Newsweek.
“Compelling companies to put backdoors into encrypted services would make millions of ordinary people less secure online. We all rely on encryption to protect our ability to communicate, shop and bank safely,” he said.