In this paper, we will propose two identity-based society oriented signature schemes that allow a group of co-signers to collaboratively generate a single signature for a message. The first proposed scheme is designated with known signers and the second scheme is with anonymous signers. Both schemes make use of pairings on elliptic curves in construction and thus have the merits of simplicity in design and efficiency in performance. In the proposed scheme with anonymous signers, a signer may participate in several different signing groups and may join or leave a signing group dynamically in a secure and efficient manner. (C) 2003 Elsevier Inc. All rights reserved.