The debate over whether tech companies should reveal user privacy to governments intensified on Sunday after Amber Rudd, the UK Secretary of State, said in an appearance on BBC's Andrew Marr show that governments should have access to encrypted messaging services like WhatsApp.
What triggered her comments was the revelation that the attacker in last week's London terror attack in Westminister used WhatsApp just minutes before he rammed a truck into a group of pedestrians.
Since WhatsApp adds end-to-end encryption to all messages sent through its platform, police were unable to identify what was communicated by the attacker.
"It is completely unacceptable, there should be no place for terrorists to hide," Rudd said, adding that services like WhatsApp should not act as "a secret place for terrorists to communicate with each other".
"But on this situation we need to make sure that our intelligence services have the ability to get into situations like encrypted WhatsApp," Rudd said.
Governments have been exploring legal ways to somehow force tech companies to co-operate with authorities and decrypt user data when needed.
In 2016, a US bill wanted tech companies to surrender user data under a judge's orders. However, companies and privacy activists opposed the bill, and it couldn't make it to a vote.
WhatsApp, which was acquired by Facebook in 2015, previously said that it had always prioritized making user data and communication as secure as possible, and that protecting private communication was one of its "core beliefs".
Although encrypted data can be extremely difficult to access, a service provider can indeed help authorities decrypt data. In addition, intelligence services can also exploit certain "backdoors" to decrypt messages.
Therefore, it won't come as surprise if WhatsApp one day comes up with a change of policy that would no longer require the app to prevent hackers or government surveillance tools from collecting your messages.
With that in mind, here are five secure mobile apps for sending encrypted messages, if WhatsApp ever backtracks.
Signal
Download: Android (free) | iOS (free)
Signal is said to be NSA whistleblower Edward Snowden's personal favourite, which essentially makes it the top contender for the most secure messaging app on the market.
It's a free app which offers completely end-to-end encrypted messaging and voice-call services to its users.
What makes Signal even more interesting is that the app is open source, allowing anyone to hunt down potential security holes and patch them.
Viber
Download: Android (free) | iOS (free)
Viber joined the end-to-end encryption bandwagon less than a year ago. The app encrypts texts and voice chats between individuals and groups, which is functional both on its desktop and mobile versions.
Viber has a special colour-coded system to shows users how protected their conversations are with contacts.
The grey colour means encrypted communications while green means encrypted communications with a trusted contact. Red, on the other hand, signifies a problem with the authentication key.
iMessage
Apple has been involved in a hard battle with authorities to keep users' data private. The company has clearly said that it doesn't record messages or attachments, and their contents are protected by end-to-end encryption. Therefore, only the sender and receiver can access the messages, not even Apple itself.
However, the communications only remain inaccessible for Apple as long as they are not backed up on iCloud. Once they end up in the cloud storage, Apple can access them and hand them over to authorities if the company is served a warrant.
Cyber Dust
Download: Android (free) | iOS (free)
Unlike iMessage, Cyber Dust is immune to even formal warrants. Messages on this app are not only encrypted end-to-end, but they are also deleted from the user's phones immediately after they are viewed.
There's even more. If someone takes a screenshot of your messages, it couldn't be attributed to you because the chats on Cyber Dust don't show usernames.
Telegram Messenger
Download: Android (free) | iOS (free)
Telegram messages can be totally private if you activate the Secret Chat mode. You can also set the messages to self-destruct.
Users can encrypt anything on Telegram, including chats, groups and media. Regular messages, on the other hand, are stored on the company servers.
