Partially　blind　signatures　allow　signers　to　include　some　common　information　(the　date　of　issue,　the　value　of　electronic　coins)　negotiated　by　signers　and　users.　This　paper　presents　an　efficient　partially　blind　signatures　scheme　with　provable　security　in　the　random　oracle　model.　Our　scheme　uses　a　public　algorithm　to　evolve　the　public　keys　and　private　keys　which　will　be　used　during　the　partially　blind　signatures　protocol.　In　such　a　manner　the　scheme　has　the　same　security　as　the　underlying　blind　Okamoto-Schnorr　signature　without　bringing　out　additional　workload.