Patent ID: 8312266

Claim:
A non-transitory computer-readable medium storing a program controlling a computer, the program causing the computer to generate verification information to verify changes made by mail servers during the delivery of an electronic mail by: extracting header information from the electronic mail, further extracting header information subject to originality guarantee from the extracted header information, and then generating a header characterization for the header information subject to the originality guarantee, and extracting message body information from the electronic mail and generating a body characterization for the message body information as well; generating a characterization set for applying a signature by combining the header characterization and the body characterization; adding verification information including the signature to said generated characterization set; linking said characterization set, including the verification information, to the electronic mail; managing the characterization set for applying the signature, including managing revisions of the characterization set generated at said process of generating the characterization set for applying the signature; and prior to generating the header characterization for a received electronic mail, extracting all of the characterization sets for applying the signatures including the verification information added by all of the computers located on routes of the delivery from the header information of the received electronic mail, comparing the extracted characterization sets for applying the signatures to each other, and confirming whether or not any change has been made for each of the characterization sets.