Certification Status of timestamp of Box Sign by JADAC

I would like to know about the certification status of Box Sign timestamps by the Japan Data Communications Association (JADAC, formerly Nippon Information Communications Association).
We would like to use Box Sign as a voucher management system under the Electronic Bookkeeping Act and as an electronic contract system under the Electronic Signature Act. As a prerequisite, the Box Sign timestamp must be certified by the Japan Data Communications Association.