IPsec has become an important supplement of IP to provide security protec-tion. However, the heavyweight IPsec has a high transmission overhead and latency, and it cannot provide the address accountability. We propose the self-trustworthy and secure Intet protocol (T-IP) for authenticated and encrypted network layer communications. T-IP has the following advantages: (1) Self-Trust-worthy IP address. (2) Low connection latency and transmission overhead. (3) Reserving the important merit of IP to be stateless. (4) Com-patible with the existing TCP/IP architecture. We theoretically prove the security of our shared secret key in T-IP and the resistance to the known session key attack of our secu-rity-enhanced shared secret key calculation. Moreover, we analyse the possibility of the application of T-IP, including its resilience against the man-in-the-middle attack and DoS attack. The evaluation shows that T-IP has a much lower transmission overhead and con-nection latency compared with IPsec.