What is the name of the first mathematical model of a multi-level security policy used to define the concept of a
secure state, the modes of access, and rules for granting access?

A.
Clark and Wilson Model

B.
Harrison-Ruzzo-Ullman Model

C.
Rivest and Shamir Model

D.
Bell-LaPadula Model

Explanation:
The Bell-LaPadula model was developed to address the security concerns of time-sharing mainframe systems
and leakage of classified information. It was the first mathematical model of a multilevel security policy
employed to define the concept of a secure state machine and modes of access, and outlined rules of access.
Incorrect Answers:
A: The Clark-Wilson model was developed after the Biba model, which was developed after the Bell-LaPadula
model.
B: The Harrison-Ruzzo-Ullman (HRU) model was NOT the first mathematical model of a multi-level security
policy used to define the concept of a secure state, the modes of access, and rules for granting access
C: Ron Rivest, Adi Shamir, and Leonard Adleman invented RSA, which is a public key algorithm that is the
most popular when it comes to asymmetric algorithms.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 369, 372-374, 815