Many methods, based on the concept of key-lock-pair have been proposed for access control in computer protection systems. However, the proposed methods still either lack of dynamic ability or need quite a lot of computation in performing requests of deleting users/files, inserting users/files, or updating access rights of users to files. In this paper we propose a two-key-lock-pair access control method that is based on the unique factorization theorem and a time stamp mechanism. Our method is dynamic and needs a minimum amount of computation in the sense that it only updates at most one key/lock for each access request, which has not been achieved before.