MKIPS: MKI‐based protocol steganography method in SRTP

Abstract

This paper presents master key identifier based protocol steganography (MKIPS), a new approach toward creating a covert channel within the Secure Real‐time Transfer Protocol, also known as SRTP. This can be achieved using the ability of the sender of Voice‐over‐Internet Protocol packets to select a master key from a pre‐shared list of available cryptographic keys. This list is handed to the SRTP sender and receiver by an external key management protocol during session initiation. In this work, by intelligent utilization of the master key identifier field in the SRTP packet creation process, a covert channel is created. The proposed covert channel can reach a relatively high transfer rate, and its capacity may vary based on the underlying SRTP channel properties. In comparison to existing data embedding methods in SRTP, MKIPS can convey a secret message without adding to the traffic overhead of the channel and packet loss in the destination. Additionally, the proposed covert channel is as robust as its underlying user datagram protocol channel.

Keywords

• covert channel
• master key identifier
• protocol steganography
• secure real‐time transfer protocol
• voice‐over‐internet protocol