Tranquility Property (Dictionary Entry)

Owned by David Doret, created
Last updated: 19-09-2021
2 min read

Tranquility Property

Alternative Forms

  • Tranquility

Definitions

Definition 1

Tranquility is a property that influences the security of systems.

Once a system state is demonstrated as statically secure, a difficulty is to further demonstrate that it is dynamically secure. Put differently, to demonstrate that given an initial secure state, subsequent state transitions always lead to a secure system. The tranquility property captures if and how modifications in the security clearance level of subjects (e.g. people) and the security classification level of objects may take place in the system. It distinguishes three possible tranquility levels:

  • Strong tranquility: This is a secure tranquility level where security clearance levels and security classification levels are first initialized and then cannot be modified during the overall lifecycle of the system. This tranquility level imposes stringent constraints on the system.

  • Weak tranquility: This is a secure tranquility level where security clearance levels and security classification levels are first initialized and then may be modified following a procedure that assures the legitimacy / authority of the person ordering the change, and the security of the system throughout the transition to the new state. This tranquility level imposes less stringent constraints on the system.

  • No tranquility: This is an insecure tranquility level where security clearance levels and security classification levels may be modified without the secure procedure required in weak tranquility. This tranquility level imposes no additional constraints on the system.

Note 1

If not specified otherwise, the tranquility property refers to both security clearance levels and security classification levels. But the concept may be applied to only security clearance levels or security classification levels, in which case it is recommended to express it explicitly.

Note 2

The tranquility principle, general means that a system shall be of strong or weak tranquility, that are secure, but not no tranquility, that is insecure.

Note 3

A system is deemed tranquil when it complies with the tranquility principle.

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