An information transmission protocol to be used in hierarchical and role-based organizations

ABSTRACT The data transferred in an organizational information system must be strictly prevented from exposing by the unautorized users. This study includes the definition of a public-key cryptosystem which can be used in hierarchical and departmental (role-based) organizations to ensure data security. The organizations are composed of departments. While general issues are related to all of the departments, some issues may be related to only one of them. In the meantime, there is a hierarchy in each department. The information may be related to the head of the department (level 1), or to the other levels also. The people in a specific level in the hierarchy is assumed to be capable of viewing the messages addressed to the lower levels too. Message distributer (MD) is responsible of generating, keeping, and distributing the keys and distributing the messages. MD will distribute a departmental and a hierarchical key to each user according to his/her department and level of hierarchy. The messages will be encrypted twice before the transmission: first using the departmental, and then the hierarchical key. This ensures that the people in the target department and hierarchy can decrypt the encrypted message and read the original message. By using "Hard Problems", it is ensured that the intruders cannot view the original message. The personel in a higher level in the hierarchy can generate the intended level's key via a simple process and decrypt the encrypted message thereafter. This way, people do not need to keep the keys for the lower levels in the hierarchy. This work includes a cryptographic algorithm designed for the hierarchical and departmental which hasn't been done before, allows production of the lower level keys via a simple calculation which disregards the necessity to hold more than two keys, so it is original. The problems used by RSA and El Gamal Scheme are used properly as a base to ensure higher security. XI