The APCO25 (P25) communications protocol is a form of digital radio communications technology growing in popularity in police and other public safety radio systems in the US and abroad. Many such systems are unencrypted and can be received on digital radio scanners. Others employ encryption in an effort to prevent civilian monitoring.
Now researchers with NICTA, Queensland Research Laboratory, Brisbane, Australia, and Griffith University, Gold Coast, Australia have published a paper documenting their exploration of the P25 standard and its encryption techniques. They report success in cracking APCO25 encryption using a new software-defined radio approach to expose the vulnerabilities of the lowest layers of the protocol stack. Their paper discusses a number of serious security flaws which lead to practical attacks that can compromise the confidentiality, integrity and availability of P25 networks.
You can download the 18 page PDF documenting this project here.