Letter Sealing is an end-to-end encryption feature that LINE has launched in order to keep your chats safe and private during transmission by scrambling the contents of your messages with an encryption key that is found only on the device you’re using and not on any servers, making it impossible for a third-party to intercept your conversations.
Right now, the feature is somewhat limited; it only works on one on one chat conversations as well as location sharing but LINE says it will be extended around other features and devices at some point in the near future.
The encryption will expand to other features and devices in the future
If you’re using LINE on a single Android device, you won’t have to do anything to enable Letter Sealing; it’s on by default. Meanwhile, those with multiple Android devices and those on devices running iOS will have to enable the feature through Settings.
End-to-end encryption has become something of a trend for messaging apps lately, especially as more and more new competitors launched that enabled the feature from the get-go. One of the biggest enablers of end-to-end encryption has been WhatsApp, which had deployed encrypted messages using Textsecure last year.