We propose a transaction length-sensitive protocol based on altruistic locking to satisfy the security requirements and improve the degree of concurrency for multilevel secure database. This protocol expended the two-way donation locking protocol in multilevel secure database, and eliminated unauthorized information flows. Altruistic locking has attempted to reduce delay effect associated with lock release moment by use of the idea of donation. An improved form of altruism has also been deployed for extended altruistic locking. We adapted XAL to multilevel secure database and we investigated limitations inherent in both altruistic schemes from the perspective of alleviating starvation occasions for transactions in particular of short-lived nature for multilevel secure database. Our protocol ensures serializability, eliminates covert channels to have preference to a lower level transaction, and reduces the starvation of short-lived transaction. The efficiency of the proposed protocol was verified by experimental results.
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