In a new post to his blog Kevin Schroeder shares an encrypted session handler he's created to keep sensitive information away from prying eyes (since session data is usually plain text). The result ended up in a component easily used in a Zend Framework application.
A little while ago I had come upon the problem of having to store sensitive data in a user session. The solution that I (and several others came upon) was creating a mechanism for storing encrypted data in a session. But what we wanted to do was build something that didn't have a single point of failure. We also wanted to build something portable. What we built was a simple Zend Framework session handler for storing sensitive data.
The class - App_Session_Secure_Namespace - extends the standard Zend namespace and uses the mcrypt functionality to encrypt (and decrypt the session data). The setup uses a cookie for the initialization vector (domain based, naturally) making it very difficult for someone to access the encrypted session information outside of the application.