Patent ID: 7685425
Filing Date: 2010-03-23
Classification: G06F,H04L

Abstract:
1. A server computer comprising: a store arranged to store at least one computer file at said server computer; a store arranged to store at least one digital signature at said server computer; each computer file having an associated digital signature created using a signing key from at least one of a plurality of third parties, said signature being stored on said server computer; a receiver arranged to receive a request from at least one other computer for access to at least one computer file stored on said server computer; means arranged to retrieve said at least one requested computer file in response to said request; means arranged to retrieve the digital signature or signatures, directly at said server computer, associated with said at least one requested computer file in response to said request; means arranged to validate, directly at said server computer, the digital signature or signatures associated with said at least one requested computer file in response to said request; and means arranged to deny said other computer access to said at least one requested computer file if the digital signature or signatures associated with each respective requested computer file is invalid; wherein, in the case where said digital signature is invalid, no further digital signature is applied by said server computer and maliciously altered documents are not sent to said other computer by said server computer.