You can use MIC on IP phones.
Manufacturing installed certificateEach Cisco IP Phone 7970 Series contains a unique manufacturing installed certificate (MIC), which is used for device authentication. The MIC is a permanent unique proof of identity for the phone, and allows Cisco CallManager to authenticate the phone.
and following url provides information on other security features in IP phones like Encryption.
http://www.cisco.com/en/US/products/hw/phones/ps379/products_administration_guide_chapter09186a00803b144c.html#wp1078325
