Which security model uses division of operations into different parts and requires different users to perform each part? 

Answer options:

A. Bell-LaPadula model
B. Biba model
C. Clark-Wilson model
D. Non-interference model

C

The Clark-Wilson model uses separation of duties, which divides an operation into different parts and requires different users to perform each part. This prevents authorized users from making unauthorized modifications to data, thereby protecting its integrity. The Clark-Wilson integrity model provides a foundation for specifying and analyzing an integrity policy for a computing system. The model is primarily concerned with formalizing the notion of information integrity. Information integrity is maintained by preventing corruption of data items in a system due to either error or malicious intent. An integrity policy describes how the data items in the system should be kept valid from one state of the system to the next and specifies the capabilities of various principals in the system. The model defines enforcement rules and certification rules. The models enforcement and certification rules define data items and processes that provide the basis for an integrity policy. The core of the model is based on the notion of a transaction. A well-formed transaction is a series of operations that transition a system from one consistent state to another consistent state. In this model the integrity policy addresses the integrity of the transactions. The principle of separation of duty requires that the certifier of a transaction and the implementer be different entities. The model contains a number of basic constructs that represent both data items and processes that operate on those data items. The key data type in the Clark- Wilson model is a Constrained Data Item (CDI). An Integrity Verification Procedure (IVP) ensures that all CDIs in the system are valid at a certain state. Transactions that enforce the integrity policy are represented by Transformation Procedures (TPs). A TP takes as input a CDI or Unconstrained Data Item (UDI) and produces a CDI. A TP must transition the system from one valid state to another valid state. UDIs represent system input (such as that provided by a user or adversary). A TP must guarantee (via certification) that it transforms all possible values of a UDI to a "safe" CDI. In general, preservation of data integrity has three goals: Prevent data modification by unauthorized parties Prevent unauthorized data modification by authorized parties Maintain internal and external consistency (i.e. data reflects the real world) Clark-Wilson addresses all three rules but BIBA addresses only the first rule of intergrity. References: HARRIS, Shon, All-In-One CISSP Certification Fifth Edition, McGraw-Hill/Osborne, Chapter 5: Security Architecture and Design (Page 341-344). and http://en.wikipedia.org/wiki/Clark-Wilson_model