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Joined 2026-09-21 Message
Incoming links: Information confidentiality
Bell-LaPadula model 2026-10-31
A classification-based information confidentiality model restricting subject accesses to prevent forbidden information flow. The simple security property restricts reading above clearance; the Bell-LaPadula star property restricts information flow through current reads and writes. It is not a complete data integrity policy.
Data integrity 2026-10-31
Protection of data against unauthorised or accidental alteration. It is distinct from information confidentiality and service availability.
First, the Bell-LaPadula model is a information confidentiality policy. It permits a low-level subject to overwrite a more highly classified object by blind writing. That can destroy a high-level file or introduce false data without disclosing its old contents. Thus it does not supply a data integrity policy, and it also does not ensure service availability. Modern multiuser operating systems require protection against modification and resource exhaustion as well as disclosure.
Second, a single hierarchy of classifications cannot express ordinary independent user ownership and selective collaboration. Two users at the same level may still need different permissions on their respective files; conversely, an authorised publication may deliberately release selected information to lower levels. The simple model lacks those owner-specific permissions and controlled release decisions. Adding discretionary access control, categories and explicit declassification mechanisms is substantial additional policy.
The Bell-LaPadula model protects information confidentiality by controlling information flow between security levels. Its simple security property says that a subject may read only objects whose classification does not exceed its maximum clearance:Thus a user cleared for confidential material cannot directly read a secret file. A readwrite permission includes reading and must satisfy the same restriction. This is an access control rule about who can learn existing contents; it says nothing by itself about where a cleared subject can subsequently copy them.