Password-based access control systems
In documentary information systems, in document management automation systems, the so-called password access control systems have become widespread, representing a separate type of mechanisms for implementing the discretionary principle of access control.
The main provisions of password systems can be formulated as follows.
1. The system is represented by the following set of entities:
a set of information objects (documents) About (o1, ..., om);
multiple users S(s1, ..., sn);
a set of passwords for accessing objects K(k1, ..., kr).
2. The system sets the mapping of the set O to the set K, set by the following function: fko : O → K.
The value of the fko(o) - ko function is the ko password for accessing the document.
3. The area of secure access is defined by a set of triples (s, k, o), each element of which corresponds to the user's possession of the object access password. As a result, the mapping of the set S to the set K is established: fks : S → K.
The value fks(s) = Ks is a set of passwords for accessing system documents known to user s.
4. The processes of user access to system objects are organized in two phases:
the document opening phase;
the phase of closing (saving) the document.
When opening the document about, user s presents (enters, transmits) to the AU security monitor the ks0 password for accessing this document.
The access request is satisfied if ks0 = fk0(o).
In case of successful opening, the user is granted the rights to work on a fixed set of operations with the object.
Two approaches are possible, corresponding to voluntary and compulsory access control methods.
When using the forced method of assigning passwords to access documents, they are changed only by a dedicated user - the system administrator.
If it is necessary to encrypt a modified object or when a new object appears in the system that is subject to discretionary access to it, the system administrator, based on a special procedure, generates an access password for the new object, encrypts the document with a key created based on the password, and fixes the new document in an encrypted state in the system. The administrator provides the password for access to this document to those users who need it. This forms a subset of access triples {(s1, k, o), (s2, k, o), ...} to the document o.
With voluntary access control, the procedure described above for forming a subset of access triples to a new document is performed by the owners of the object.
The advantage of password systems compared to discretionary access control systems based on an access matrix is that they do not have an object associated with a security monitor that stores information about access control to specific objects.
This object is the most security-critical object of the system.
In addition, password systems ensure security even when unauthorized persons have unlimited or technically possible access to the media on which encrypted objects are recorded and stored.
These advantages of password-based access control systems make them extremely widely used in documentary information systems.
Despite the fact that discretionary models were developed almost 40 years ago, and that numerous studies have shown their limited protective properties, these models are widely used in practice. Their main advantages are simplicity and maximum detail in the organization of access.
