Restore data from encrypted iOS backup without respective device
You can decrypt an iTunes Encrypted Backup (when the password is known) using backup_tool.py from iphone-dataprotection on Google Code.

Navigate to an suitable destination in Terminal, then run the following:

hg clone https://code.google.com/p/iphone-dataprotection/
python iphone-dataprotection/python_scripts/backup_tool.py ~/Library/Application\ Support/MobileSync/Backup/backupname decrypted


Replace backupname with the encrypted backup folder name.

The tool will prompt you for the encryption password, then output the decrypted backup to the folder ‘decrypted’.