WhatsApp is rolling out multi-device support for Android and iOS users, but many users are complaining that their security codes have changed as a result. According to WhatsApp, the security code change is likely during the early stages of the multi-device feature’s introduction. The capability allows users to connect up to four linked devices without having to connect the phone. In a tweet, Wabetainfo stated that the messaging app intends to deliver warnings regarding security code changes when the user re-registers the account on a new phone. According to the source, WhatsApp does not alert users when they delete or link devices.
Every chat has a unique security code and can be used to verify that the messages that you send to your contacts are end-to-end encrypted. “End-to-end encrypted chats between you and one other person have their own security code used to verify that the calls and the messages you send to that chat are end-to-end encrypted. This code can be found in the contact info screen, both as a QR code and a 60-digit number. These codes are unique to each chat and can be compared between people in each chat to verify that the messages you send to the chat are end-to-end encrypted. Security codes are just visible versions of the special key shared between you – and don’t worry, it’s not the actual key itself, that’s always kept secret,” WhatsApp said.
If you or a contact reinstalls WhatsApp or switches phones, the security codes on WhatsApp may also change. You may also enable it if you do not receive notifications when the security codes between you and your contacts change. It should be noted that the feature is only available to contacts in an end-to-end encrypted chat.