A device for facilitating verification of an electronic signature in an exchange of instructions between an in-house server and an outside server. Each server which is to execute a partial process of a cooperative service has, in a key storage unit (206), secret keys corresponding to public key certificates issued by an in-house CA and by an outside public CA. A signature key selection unit 216 judges whether a server which is to execute a process next is a device within or outside the company and selects an in-house secret key when the next server is an in-house device and an outside secret key when the next server is an outside device. A signature creation unit (218) calculates a value of an electronic signature for an job flow instruction to the next server using the selected secret key. An instruction division/integration unit (204) transmits to the next server the job flow instruction with the electronic signature value attached.