This document discusses security aspects of mobile cloud computing. It begins with an abstract discussing how cloud computing offers scalable and secure computation resources as a service. Mobile cloud computing combines mobile computing, cloud computing, and wireless networks. The document then analyzes existing security challenges and issues in cloud and mobile cloud environments. It identifies key long-term security and privacy issues based on documented problems. The document provides an overview of cloud computing models, characteristics, architectures, and security issues. It discusses how the flexibility and openness of cloud environments challenge assumptions about application security.