Image forming apparatus, printing method and control program

A printing method to be employed in a system, which is constituted by:

• a terminal device that creates print data and issues a print instruction;
• an image forming apparatus that produces a print product including a plurality of print objects, which are represented by the print data;
• and a communication network through which the terminal device and the image forming apparatus are coupled to each other, the printing method comprising:
• transmitting the print data to which digital signatures are attached from the terminal device to the image forming apparatus;
• determining whether the digital signature is valid or invalid in the image forming apparatus, so that the image forming apparatus conducts a printing operation, based on a result of determining whether the digital signature is valid or invalid;
• wherein, when the plurality of print objects includes both a valid print object for which the digital signature is determined as valid and an invalid print object for which the digital signature is determined as invalid, the printing operation is controlled in such a manner that an operation for printing the valid print object is enabled, while another operation for printing the invalid print object is disabled.

A computer readable medium storing a computer executable program for making an image forming apparatus produce a print product including a plurality of print objects, which are represented by print data, the program comprising program code for causing the image forming apparatus to perform the steps of:

• conducting a printing operation based on the print data, so as to create the print product;
• and
• determining whether the digital signature is valid or invalid, so as to control the printing operation to be conducted by the image forming apparatus, based on a result of determining whether the digital signature is valid or invalid;
• wherein, when the plurality of print objects includes both a valid print object for which the digital signature is determined as valid and an invalid print object for which the digital signature is determined as invalid, the printing operation is controlled in such a manner that an operation for printing the valid print object is enabled, while another operation for printing the invalid print object is disabled.