A modified identity-based encryption system for messaging applications

Official URL: http://192.168.1.20/record=b1226359 (Table of Contents)

Identity-based encryption (IBE) systems are relatively recently proposed; yet they are highly popular for messaging applications since they offer new features such as certificateless infrastructure and anonymous communication. However, recent studies also reveal that the infrastructure needed for IBE systems may be as complicated as the conventional public key cryptosytems and not sufficient research has been conducted in relevant issues concerning the infrastructure. Firstly, there is the issue of the existence of the Private Key Generator (PKG) as a full-trusted third party. Since PKG generates and knows users’ private keys; the user privacy has not been fully achieved. This issue leads to non-repudiation problem where PKG can not only decrypt messages but also can fabricate a valid signature on behalf of any registered user. Secondly, the key-revocation leads tremendous calculations for PKG. In the case of a key-lost, finding a descriptive identity for a user may be difficult. Thus, a new master secret key is generated resulting in changing private keys of every user registered in the system. With this thesis, a new modified IBE infrastructure is proposed to overcome the stated problems. The master key is secretly shared by two parties, Registration Authority (RA) and Private Key Generator (PKG). In addition, PKG shares the master key with every registered user. With this approach, PKG will not be able to acquire the master key provided that there will be no collusion between the parties, RA-PKG and PKG-users.