Classical anonymous credential systems aredesigned for center-controlled networks, and not applicablefor ad hoc networks. The existing pseudonym schemesdo not thoroughly address the issue in ad hoc networks.Therefore, this paper proposes a self-generated anonymouscredential system for ad hoc networks, where a node generatesvalid pseudonyms itself without the participation ofan organization management center, and the frequency ofpseudonym-generation is controllable. The formal specificationof the proposed system is not defined based onzero-knowledge protocols and classic pseudonym models,but based on the ideal functionality for common certification.To implement a practical system, a modular methodologyis used, where a pseudonym-based signature schemeis proposed, and then a tag-based signature protocol ispresented. Finally, the whole system is constructed. Thesecurity of our scheme is proved in the ideal-system/realsystemmodel.