How can I access data (such as WiFi keys) in an encrypted Titanium backup?
I have found a working solution on GitHub:
https://github.com/phyber/TiBUdecrypter

1. Install/upgrade dependencies (on Ubuntu)

apt-get install python2.7
pip install --upgrade docopt
pip install --upgrade six
pip install --upgrade PyCrypto


2. Get script from GitHub


Download: https://github.com/phyber/TiBUdecrypter/archive/master.zip
Extract the ZIP


3. Decrypt a backup

python2.7 tibudecrypt.py com.keramidas.virtual.XML_WIFI_AP_LIST-20140711-012128.xml.gz