Modified Chen-Hwang identity-based conference key broadcast schemes with user authentication

Abstract

In 1994 Chen and Hwang proposed two identity-based conference key broadcast schemes with user authentication. The conference key of their schemes can be distributed knowing only the receivers' identities. Only one copy of the ciphertexts is required to broadcast to all users. Their schemes are more efficient on transmissions and computational complexity than previous works. However, this paper identifies two problems in their schemes. Two modified schemes will be proposed to solve these problems.