We propose a vehicular network trust model that integrates cryptography-based entity trust and email-based social trust. The entity trust provides security protections such as origin integrity, data integrity, and confidentiality. The social trust provides a level of belief on the data transmitted by an entity. To achieve the email-based social trust, we require each user to run an automated agent that performs trust evaluation checks and processes trust checking requests. The requests are from their highly trusted contacts or through a trusted proxy server maintained by the email service provider. We utilize identity-based cryptography (IBC) to integrate entity trust and social trust. This allows us to use a unique identity (e.g., an email address) for each entity. Further, we use the IBC based attribute based cryptography to develop secure group communications in vehicular networks. Finally, we present research challenges and potential research directions to extend this work.