Line launches message encryption feature Letter Sealing

As the battle between privacy and security heats up, one instant messaging service has definitively announced which side of the divide it falls on.

Line, which is estimated to have more than 200 million monthly active users, has launched a new end-to-end encryption feature called “Letter Sealing” for use across both smartphone and desktop platforms.

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Using a similar approach to security protocols implemented by the likes of WhatsApp and iMessage, Letter Sealing uses a private key stored on the user’s device to encrypt messages, making it impossible for the content to be disclosed to a server or third party. Both participants in a chat must have Letter Sealing activated for their correspondences to be protected, but users can easily turn the feature on by going to Settings in any version later than LINE 5.3.0.

Line has implemented a number of security features in the past, including Hidden Chat and Passcode Lock, and software engineer JI believes that the latest addition could provide a valuable service to users.

“Letter Sealing is functionally different from existing methods,” he explains. “One key difference is that with Letter Sealing, encryption is performed by the sender instead of the server. This technically prevents any possibilities of messages being decrypted and re-encrypted, and also makes sure messages are never exposed in plain text on the server. Additionally, the message keys used to exchange messages are safely stored on the devices of the sender and recipient instead of the server. This eliminates the possibility of a third party, including the LINE servers, from removing the seal on messages.”

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While privacy advocates are sure to be pleased about Line’s new security protocol, some national governments have argued that encrypted messages could enable terrorists to communicate undetected. Both the FBI and UK Prime Minister David Cameron have argued that encryption poses a threat to national security, but others see their concerns as a smokescreen to impose restrictions on individual liberty.