Synchronization of Transactions to Prevent Illegal Information Flow in a Role-Based Access Control Model

The role-based access control (RBAC) model is widely used to make information systems secure. Even if every access request is authorized in the roles, illegal information flow might occur as the well known confinement problem. In this paper, we discuss how to prevent illegal information flow to occur by synchronizing conflicting transactions in the RBAC model. We first define types of information flow relations, legal (LIF), illegal (IIF), and possibly illegal (PIF) ones R₁ = R₂, R₁ rarr R₂, and R1 rarr R₂ among a pair of role families R\ and Ri, respectively. Here, let T₁ and T₂ be a pair of transactions with role families R₁ and R₂ respectively. Suppose T₁ precedes T₂ in a schedule, i.e. for every pair of conflicting methods op\ and opi from T\ andT% respectively, op\ is performed prior to op₂- Here, if the LIF relation R₁ = R₂ holds, no illegal information flow occur. If R₁ rarr R₂, illegal information flow necessarily occur. R₁ rarr R₂ implies that illegal information flow might occur depending on in which order the transactions perform what methods.