For encrypted backups, the backup files are encrypted using the AES256 algorithm in the CBC mode, with a unique key and a null initialization vector (IV). The unique file keys are protected with a set of class keys from the Backup keybag
. The class keys in the Backup keybag
are protected with a key derived from the password set in iTunes through 10,000 iterations of Password-Based Key Derivation Function 2 (PBKDF2). Both open source and commercial tools provide support for encrypted backup file parsing if the password is known. Some tools won't even prompt for a password, which makes them useless in a forensic investigation. Other tools will attempt to crack the password.
Elcomsoft Phone Breaker is a GPU-accelerated commercial tool from Elcomsoft developed for the Windows platform. The tool can decrypt an encrypted backup file when the backup password is not available. The tool provides an option to launch a password brute-force attack on the encrypted...