Efficient registration procedure for multi-domain authentication for mission critical communication services

The 3rd Generation Partnership Project (3GPP) forum [1] decided to establish a standard for Mission Critical Push-to-Talk (MCPTT) Communications over Long-Term Evolution (LTE) for Release 13. MCPTT systems utilized by public safety (PS) agencies enable their personnel to selectively and sequentially transmit messages to one another, either on a one-to-one or one-to-many basis over LTE. MCPTT service domain is usually operated by an entity (PS agency) different from the entity operating LTE (and IP Multimedia Subsystem (IMS)) domain. In such cases, each domain may have to provide their own identity and execute their own security mechanisms to ensure authenticity and privacy of PS users, while adhering to stringent call setup time requirements. However, existing Session Initiation Protocol (SIP) registration procedure which is considered as the signalling protocol for MCPTT, is suitable only in scenarios where IMS and Application Service domains belong to the same operator or at least a mutual trust is established between the operators of two domains. Hence for MCPTT service operated within multiple domains (signalling plane and application plane are operated by different operators), it is required to design a suitable user authentication procedure in addition to signalling plane authentication using SIP while also ensuring the confidentiality of the identity. In this paper, we propose an efficient MCPTT service registration procedure, for authentication of identities (with confidentiality) between multiple domains for mission critical communication services.