Security Analysis of Voice-over-IP Protocols

The transmission of voice communications as datagram packets over IP networks, commonly known as Voice-overIP (VoIP) telephony, is rapidly gaining wide acceptance. With private phone conversations being conducted on insecure public networks, security of VoIP communications is increasingly important. We present a structured security analysis of the VoIP protocol stack, which consists of signaling (SIP), session description (SDP), key establishment (SDES, MIKEY, and ZRTP) and secure media transport (SRTP) protocols. Using a combination of manual and tool-supported formal analysis, we uncover several design flaws and attacks, most of which are caused by subtle inconsistencies between the assumptions that protocols at different layers of the VoIP stack make about each other. The most serious attack is a replay attack on SDES, which causes SRTP to repeat the keystream used for media encryption, thus completely breaking transport-layer security. We also demonstrate a man-in-the-middle atta...

• Type: Conference
• Year: 2007
• Where: CSFW
• Authors: Prateek Gupta, Vitaly Shmatikov
• Keywords: CSFW 2007, Insecure Public Networks, Security Privacy, VoIP, VoIP Protocol Stack