Anonymous conference key distribution systems based on the discrete logarithm problem

In 1997, Wu proposed a conference key distribution system (CKDS) with user anonymity using algebraic operations. User anonymity is, in which the identities of participants in a conference are anonymous to each other, except for the chairperson. In this article, two CKDSs with user anonymity are proposed. One is a modified one of the Wu's scheme that uses simple interpolating properties of polynomials to replace the algebraic approach. Both the Wu's original scheme and our modified one require a one-way hash function to hide the identities of participants and to protect each participant's common key shared with the chairperson. Both schemes also use the one-way hash function to provide the authentication for the chairperson. Moreover, we propose another scheme which does not use a one-way hash function, but also achieve the same purposes. Compared to the Wu's scheme, both our schemes require less computing time. The security of the proposed CKDSs is based on the difficulty of computing the discrete logarithm problem as well as the one-way hash cryptographic function assumption. Both schemes are secure against impersonation and conspiracy attacks.