Sensing data generated by connected and automated vehicles (CAVs) are crucial for vehicle control and planning. Additionally, these data can also be shared with transportation management center to support traffic control and emergency responses in future intelligent transportation systems. However, security issues arise if these data are inaccurate and flawed due to sensor vulnerabilities in extreme environment conditions or malicious attacks on data transmission modules. In this talk, I will first review security issues regarding data trustworthiness and privacy preservation in CAV environment. The second part of this talk will introduce a novel protocol for V2I security, titled Proof of Travel (POT), which allows road infrastructure to verify the authenticity and correctness of vehicle-shared data and incentivize the data-sharing activities. In particular, the POT protocol builds upon the physical law of vehicle movement and cryptography mechanisms. A case study on V2I-reported data validation will be given to illustrate the usage of the protocol. I will conclude by discussing challenges faced by engineers in developing and implementing security solutions in real-world projects.