A study of SIP and H.323 protocol security in VoIP signalling

VoIP is one of the commonly used services on internet. It provides a very important role in the field of communication. Since voice is transferred over the public network, where it is very easy to impersonate or modify data during transmission, there is a need for security mechanisms to protect the data. Many security mechanisms are already defined in the standards but they also have some limitations and many security problems remain unsolved. This paper focuses on the security aspects of the two commonly used protocols for VoIP signalling: SIP and H.323. During the comparative study, it is found that SIP is having more security mechanisms and thus less prone to error than H.323. TLS allows only those SIP entities to authenticate servers with whom they have a direct connection.