Michael,Kurt Thanks for your help very much. I've found my error. The correct lines should be: m[1].mod_op=LDAP_MOD_ADD|LDAP_MOD_BVALUES; m[1].mod_type="usercertificate;binary"; b[0]=bvp; b[1]=NULL; m[1].mod_bvalues=b; Best regards, cellecial ---------------------------------------------- »¶ÓʹÓà 21CN µç×ÓÓʼþϵͳhttp://www.21cn.com Thank you for using 21CN Email system