Line Brings Optional End-To-End Encryption To All Platforms, Default On Android

Line, a messaging application that's popular mainly in Japan (but also in a few other countries), announced that starting with version 5.3.0, end-to-end encryption will be supported on Android, iOS, Windows and Mac OS X. The feature is called Letter Sealing, and it will work by default on Android.

This feature makes Line one of the first to offer end-to-end encryption, even as an option, on both the mobile and desktop platforms. The only other app that does this is Telegram, but Line has an advantage here because its encryption works by default on Android, and this will be adapted in the future to work the same way on all platforms. Meanwhile, Telegram's E2E encryption will likely remain an option only (unless its creators overhaul its E2E protocol).

As with any end-to-end encryption protocol, the chats will be encrypted with a key that is stored on the user's device instead of a centralized server. Line claimed that it's "technically impossible for the chat content to be disclosed in the server or to a third party."

For now, the E2E encryption will only apply to one-on-one chats and Location Sharing. The only asynchronous E2E encryption protocol that can handle group chatting right now is the one used in Open Whisper System's Signal/TextSecure application, which Edward Snowden and other cryptographers have recommended for maximum communications privacy. Signal is also an open source application with an open source E2E encryption protocol, whereas Line's protocol is proprietary and for now not much is known about how it works exactly.

Line comes with other security features as well, such as Hidden Chat, a time limited messaging feature, a Passcode Lock, and a four-digit security pin. The company has also created a Bug Bounty program, to encourage others to find whatever vulnerabilities the app may have, so they can be fixed.

Since March 2013, Line has also received global security certifications such as SOC 2 and SOC 3 (formerly known as SysTrust). In its recent blog post, Line also said that it will "continuously strive to advance its top-class security system to offer the safest communication platform for users worldwide."

Until the default E2E encryption is adapted to the other platforms, non-Android users will have to manually enable Letter Sealing at More > Settings > Chats & Voice Calls > Letter Sealing.


Lucian Armasu joined Tom’s Hardware in early 2014. He writes news stories on mobile, chipsets, security, privacy, and anything else that might be of interest to him from the technology world. Outside of Tom’s Hardware, he dreams of becoming an entrepreneur.

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Lucian Armasu
Lucian Armasu is a Contributing Writer for Tom's Hardware US. He covers software news and the issues surrounding privacy and security.
  • dE_logics
    That's ok, but when are we going to use standardized protocols to end the client and platform monopoly of various 'apps'.