1. An information processor for realizing a service by allowing a plurality of job processors, each executing a process according to a process description written in instruction data, to cooperatively operate, the information processor comprising: a signature unit for electronically signing a portion of the process description written in the instruction data to be executed by the job processor; and a transmission unit for transmitting the instruction data electronically signed by the signature unit to a job processor for executing a process indicated in the process description.