Letter Sealing is a feature that provides end-to-end encryption (E2EE) for chat room messages. E2EE is a communication system designed so that messages saved on our servers are encrypted and cannot be read by anyone except the sender and receiver of the message.
Once the sender and receiver have both turned on Letter Sealing, they will be able to start sending messages with added security.
The following information will be encrypted:
• Text messages (not including messages sent through other services)
• Location information
• 1-on-1 free voice calls
Note: We plan to expand Letter Sealing’s functionality in the future.
If you use LINE for PC after turning on Letter Sealing, you'll be required to verify your identity the first time you send a message.
To verify your identity, please refer to the following Help article:
Letter Sealing will be turned ON for the initial setup.
If you are using the iOS version of LINE and Letter Sealing is turned ON, you will not be able to preview messages.
We recommend keeping Letter Sealing turned ON at all times in order to protect your messages. However, if you would like to change the settings, please refer to the steps below.
Please be sure to follow the steps on the smartphone version of LINE. If you are accessing this Help article from your smartphone, tap here to move to the settings screen.
1. Tap More > Settings > Privacy.
2. Turn OFF Letter Sealing.
When verifying your identity on the PC version of LINE, if the screen to enter the verification code for Letter Sealing does not appear on the smartphone version of LINE, please try the following:
1. Start the smartphone version of LINE.
2. Go to More > Settings > Privacy.
3. Turn Letter Sealing OFF, then turn it back ON again.
Afterwards, please refer to the following Help article and try verifying your identity once again.
Key fingerprints are unique encryption keys that Letter Sealing gives to each user so they can send messages to one another safely and securely.
Note: The actual keys are kept secret and will not appear in LINE chat rooms.
If your key fingerprint matches your friend's, it means your chat is securely encrypted. To check whether your key fingerprints match, follow the steps below.
Note: Key fingerprint confirmation is optional.
1. Tap the menu icon at the top of the chat screen.
2. Tap This chat is protected with Letter Sealing at the bottom of the screen.
3. Compare the key fingerprints on your device and your friend's device.
Note: To compare key fingerprints with your friend, we recommend meeting face-to-face or using a form of communication you trust.
If "This chat is protected with Letter Sealing" doesn't appear, it means Letter Sealing is turned OFF. To turn Letter Sealing ON, follow the steps in this Help article.
To check whether a chat is protected with Letter Sealing, tap the menu icon at the top of the chat screen.
If Letter Sealing is enabled, you'll see "This chat is protected with Letter Sealing" at the bottom of the screen.
Note: You'll also see a lock icon at the beginning of the sentence.
If "This chat is protected with Letter Sealing" doesn't appear, see this Help article.