In 1999, Tseng and Jan [Comput. Commun. 22 (1999) 749] proposed two conference key distribution systems (CKDS) with user anonymity based on the discrete logarithm problem and the interpolating properties of polynomials. Their first CKDS scheme uses a one-way hash function to hide the identities of the participants and to protect each participant's common key that is shared with the chairperson. In this article, we will propose a more efficient CKDS scheme with user anonymity that is based on the elliptic curve discrete logarithm problem and the properties of the line. Our scheme has the advantage of requiring less computing time than the Tseng-Jan CKDS with a one-way hash function.