that badpadding error on read usually means the stored value cant be decrypted anymore, the keystore key it was encrypted with got invalidated or changed by the os update. sadly that stored token is not coming back, so the practical fix is to catch the platformexception when you read on startup, wipe the secure storage, and send the user to login fresh instead of leaving them stuck. it also helps to make sure youre on a recent flutter_secure_storage version, the older cipher implementation seems to hit this more after updates on samsung devices. annoying, but at least a clean re-login gets people back in.