Signal protects all one-to-one and group chats with end-to-end encryption by default. But you can still be vulnerable to man-in-the-middle attacks. To stay safe, here̵
Each contact in Signal has its own unique security code. This is a long 60 digit numeric code. To verify the end-to-end encryption between you and the contact, all you need to do is match these two pairs of 60-digit codes. But that can be quite a lot, so you can also use a QR code to verify.
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The security number changes when your contact changes their phone number or reinstall the Signal app. If the security number changes frequently, it could be a sign that something is wrong. It could be a man-in-the-middle attack or someone else using the contact’s account.
Therefore, Signal recommends that you check and verify the security number regularly, especially when sharing sensitive information with a contact.
To get started, open the Signal app on your iPhone or Android smartphone. Then open the chat whose security number you want to verify. Tap the contact’s profile name at the top here.
Now select the option “View security number”.
You will see a QR code at the top of the screen and a 60-digit security number at the bottom. This is your security code for the contact person.
You must ask your contact to share their number.
Tap the share icon to share your security number with them. The icon looks slightly different on Android.
Select the “Copy” button here.
From there, paste the number into the text field for the contact and tap the send button.
If the two security numbers match, you are golden.
If you don’t want to manually compare the 60 digit code, you can also use the QR code. This can be done easily if both devices are in the same place.
In the “Verify security number” screen, tap the QR code.
Ask the contact now to display their QR code with the security number. Once the QR code has been scanned with your phone’s camera, Signal will let you know if the code matches. If so, you can choose to mark the contact as verified using the “Mark as verified” option.
This makes it easier for you to know when end-to-end encryption is secure and enabled for a contact.
You can repeat this process for other contacts. Signal recommends that you verify the security number periodically, especially after the contact changes their number or moves devices.
Confused between Signal and Telegram? Read our Signal vs. Telegram comparison guide to find out which secure messaging app is best for you.
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