R2BAC

a risk enabled role—based model for multi-domain secure interoperation

was proposed to adapt to the dynamics of distributed environments.R2BAC employs a flexible mechanism to establish interoperation between domains

eliminating the need of a trusted third-party.It translates the problem of interoperation establishment into an op-timality problem

thus achieving optimal interoperability on the premise of domains’ security.The creation and abolish-ment of interoperation relationships in R2BAC are in accord with the dynamics of distributed environments

where do-mains join and leave in an ad hoc manner.Furthermore

R2BAC incorporates risk management methods

leading to at least two advantages.First

a fine-grained authorization mechanism is enabled;second

it is possible to monitor users’ behaviors and adjust their permission sets in a real time manner.