i didn't insert the password when i was backing up but when i choose restore from backup itunes ask me "passsword" ? Help me please.

The password and encryption for your iPhone's backup cannot be enabled by itself. The chosen password for the backup must be entered twice for verification.

If you don't remember the password for your iPhone's backup, you can't restore your iPhone from the backup. Doubtful if the FBI or similar would be able to gain access to an encrypted iPhone backup.