Mobile agents offer a new possibility for the development of applications in distributed systems and are no longer a theoretical issue since different architectures for their implementations have been proposed. With the increasing market of electronic commerce it becomes an interesting aspect to use autonomous mobile agents for electronic business transactions. Being involved in money transactions, supplementary security features for mobile agent systems have to be ensured. In this paper we present an architecture for a mobile agent system which offers fault tolerance for the whole agent system at a high level. This architecture additionally guarantees security for the host as well as security for the agent.To handle these issues for mobile agents we use various encryption mechanisms and we apply a novel method for mobile agent systems by using distributed transactions in our architecture. Due to this security architecture an agent will be enabled to carry out money transactions.