Two tier protocol for hierarchical access control in medical image transmission

The main aim of this research is to develop hierarchical access control model by which medical images sent to low class users like medical assistants can also be seen by physicians who are higher in the hierarchy whereas the vice-versa is not allowed. To provide hierarchical access control, symmetric polynomial based scheme is used. At the receiving end the key can be derived by all the class controllers which are higher in the hierarchy using symmetric polynomial and the medical image file can be retrieved. To deal with more number of users in each class the protocol is divided into two layers. The upper layer is based on symmetric polynomial and takes care of class level dynamics and the lower layer takes care of user dynamics and implemented using GDH protocol. The key is used for hiding the medical images in different bit locations of host media without inviting suspicion. During transmission the image is hidden using the symmetric polynomial key for a short period and within each and every ancestor class, the image is hidden using the corresponding GDH key. The image is hidden in an audio file. Hence this makes the scheme secure and suitable for large dynamic groups.