Role Safety in a Flexible Read-Write Abortion Protocol

In information systems, illegal information flow among objects has to be prevented. A transaction illegally reads an object if the object includes data in other objects which are not allowed to be read. In our previous studies, the flexible read-write-abortion with role sensitivity (FRWA-R) and object sensitivity (FRWA-O) protocols are discussed to prevent illegal information flow. Here, a transaction is aborted with some probability once illegally reading an object. The abortion probability depends on the sensitivity of roles which the transaction holds and objects which the transaction illegally reads. The role sensitivity and object sensitivity show how many transactions which hold the role and illegally read the object are aborted after illegally reading the object, respectively. Here, the sensitivity just monotonically increases each time a transaction is aborted. In this paper, we newly propose a safety concept of a role and an FRWA with role safety (FRWA-RS) protocol where the safety of a role increases and decreases if a transaction holding the role and illegally reading objects commits and aborts, respectively. A transaction with safer roles is aborted with smaller probability. In the evaluation, we show a fewer number of transactions are aborted in the FRWA-RS protocol than the RWA protocol while more than the WA protocol and transactions are more efficiently performed than the WA protocol.