Signal, the secure messaging application, ties itself to your phone number. For extra protection against thieves stealing your phone number, you can enable Registration Lock, preventing anyone from registering another account with your phone number. Your Signal account is tied to your phone number, which means you don’t even need a password to log in. Your Signal account can only be linked to one phone number, so you can only have Signal active on one iPhone or Android smartphone at a time.

To sign up again on a new device, you’ll need access to your number (usually via your SIM) so that you can receive a code to prove who you are.

Registration Lock prevents your account from being re-registered on another device without the PIN you used to sign up for Signal being provided. With Registration Lock enabled, whoever gets ahold of your SIM or Google Voice account will also need to know your PIN to use your account.

Signal will block your account for a week if you enter the wrong PIN a few times. If you forget your PIN, Registration Lock will expire seven days after inactivity (This is reset each time you access your Signal account from a linked device.). Once Registration Lock has expired, you will be able to re-register your number without a PIN.

Telegram has an app-based passcode lock system. This passcode lock needs to be set up on each device individually. The passcode isn’t synced between your devices, and it isn’t linked to your Telegram account. If you forget the passcode, you’ll need to delete and reinstall the Telegram app.

You’ll get all your Telegram chats back if this happens, but you will lose out on all the Secret Chats. The messages are deleted, as they aren’t synced using Telegram’s servers and are instead stored locally on the device.