Certificate　revocation　is　an　outstanding　problem　in　PKI.　This　paper　extends　Naor＇s　scheme　of　dynamic　hash　tree　in　order　to　optimize　performance.　Set　of　revoked　certificates　is　divided　into　groups.　In　each　group,　Proofs　for　certificate　status　are　computed　by　using　one-way　accumulator,　while　all　groups　are　still　organized　in　hash　tree.　The　main　advantage　of　the　proposed　scheme　is　that　it　can　adjust　traffic　between　CA-to-directory　and　directory-to-user　according　to　certificate　update　rate　and　query　rate　in　applications,　thus　can　remarkably　reduce　overall　traffic　consumed　for　certificate　revocation,　and　can　efficiently　accommodate　a　wide　range　of　scenarios.　Compared　with　Naor＇s　origin　scheme,　performance　analysis　shows　it　can　reduce　traffic　by　about　50%　in　typical　environments.　©　2004　IEEE.