This password you are being prompted for is the iTunes backup password for encrypted backups, and the software cannot read the messages out of the backup without it. This means at some point in the past you would have chosen to encrypt your iPhone backup with a password in iTunes.
If you don’t remember setting one, we recommend trying a few different passwords for the backup. A blank password often works, also just pressing o.k. without typing anything might work. Your lock screen password might also work, as well as some other old passwords. We don’t have any limit in Decipher TextMessage regarding how many attempts you can make, if you want to try several!
If the phone was setup by your work IT department, they may have also set up the password for your encrypted backup.
If you are on a Mac, your backup password may be stored in your macOS keychain. Here’s how to look for your iPhone backup password in the Mac keychain:
- Open the Keychain Access app from Applications/Utilities or by searching keychain in Spotlight.
- In “Categories”, select All Items.
- Search for iPhone in the search field in the upper right corner.
- If you see an “Application Password” named “iPhone Backup”, double click it and select “Show Password” to see the password.
You may be prompted for your macOS password to get permission to see the backup password.