On Mutually-Exclusive Roles and Separation of Duty

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Author

Ninghui Li, Ziad Bizri, and Mahesh V. Tripunitara

Tech report number

CERIAS TR 2004-21

Entry type

techreport

Abstract

Separation of Duty (SoD) is widely considered to be a fundamental principle in computer security. A Static SoD (SSoD) policy states that in order to have all permissions necessary to complete a sensitive task, the cooperation of at least a certain number of users is required. In Role-Based Access Control (RBAC), Statically Mutually Exclusive Roles (SMER) constraints are used to enforce SSoD policies. In this paper, we pose and answer fundamental questions related to the use of SMER constraints to enforce SSoD policies. We show that directly enforcing SSoD policies is intractable (coNP-complete), while checking whether an RBAC state satisfies a set of SMER constraints is efficient. Also, we show that verifying whether a given set of SMER constraints enforces an SSoD policy is intractable (coNP-complete) and discuss why this intractability result should not lead us to conclude that SMER constraints are not an appropriate mechanism for enforcing SSoD policies.

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Date

2004 – 10 – 31

Institution

CERIAS

Key alpha

LBT04

Affiliation

Purdue University

Publication Date

2004-10-31

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@Techreport{ LBT04,
	title = "On Mutually-Exclusive Roles and Separation of Duty",
	author = "Ninghui Li, Ziad Bizri, and Mahesh V. Tripunitara",
	year = "2004",
	month = "10",
	institution = "CERIAS",
	day = "31",
	abstract = "Separation of Duty (SoD) is widely considered to be a fundamental
principle in computer security.  A Static SoD (SSoD) policy states that
in order to have all permissions necessary to complete a sensitive task,
the cooperation of at least a certain number of users is required. In
Role-Based Access Control (RBAC), Statically Mutually Exclusive Roles
(SMER) constraints are used to enforce SSoD policies. In this paper, we
pose and answer fundamental questions related to the use of SMER
constraints to enforce SSoD policies.  We show that directly enforcing
SSoD policies is intractable (coNP-complete), while checking whether an
RBAC state satisfies a set of SMER constraints is efficient. Also, we
show that verifying whether a given set of SMER constraints enforces an
SSoD policy is intractable (coNP-complete) and discuss why this
intractability result should not lead us to conclude that SMER
constraints are not an appropriate mechanism for enforcing SSoD
policies.
",
	affiliation = "Purdue University",
}