How to Password Protect Your Telegram Chats for Extra Security?
If you're using Telegram's "Secret Chats" feature, which provides end-to-end encryption for your messages, then I highly recommend locking the app itself with a password, PIN, or password. While your phone itself may already have a secure lock screen, if it gets compromised, you'll at least have an extra layer of security around your important conversations.
This is important because all your secret chats in the Telegram Messaging App are stored only on your device and the recipient's device. These are the only two points of access to these encrypted messages. So if your messages are important enough to warrant that you use end-to-end encryption, they are important enough to lock down another mechanism.
How to set passcode lock for iPhone?
Next, you'll need to choose a four-digit passcode and verify it on the following screens. After that, you will see more options in the password lock settings.
By default, Telegram will automatically lock if you leave the app for 1 hour, but you can change it to 1 minute, 5 minutes or 5 hours. You can also disable this, but I don't recommend it.
If a four-digit passcode is not secure enough for you, you can turn off "Simple passcode". Enter your current four-digit passcode on the next screen, then choose a stronger alphanumeric passcode and confirm.
You can also turn on "Use Touch ID" to use your fingerprint instead of a password to unlock the Telegram app. After enabling this feature, you can still use your password at any time.
You can also lock Telegram manually from the "Chats" tab if you don't want to wait for the automatic lock to kick in, or you disabled it for some reason. At the top of the screen, just tap the open lock icon at the top and it will appear locked. Of course, it won't actually lock until you log out of the app, but once you do, you'll need to enter your passcode or Touch ID (if set up) to get back in.
How to set up a PIN or combination lock on Android?
When prompted, enter a four-digit PIN of your choice or tap "PIN" and select "Password" to choose a more secure alphanumeric passcode. Then, confirm your PIN or password.
On Android, the "Use Fingerprint Unlock" option is turned on by default, so you can use your fingerprint to unlock as long as you have registered your fingerprint on the phone. You can also set auto-lock to 1 minute, 5 minutes, 5 hours or never.
Also, just like in the iOS version, you can manually lock the Telegram app by tapping the open lock icon in the upper right corner of the chat view, then exit the app. The next time you turn it on, you'll have to use your fingerprint, PIN, or password, depending on what you're using.
In my opinion, this is one of the reasons why Telegram is better than other security-focused messaging apps like Signal Private Messenger. While Signal allows you to set a passcode to lock the app on Android, there is no such option on iPhone.