Computer-implemented method and system for embedding and authenticating ancillary information in digitally signed content

Abstract

A computer-implemented system and method for embedding and authenticating ancillary information in digitally signed content are disclosed. The method and system include: loading digital content containing a digitally signed portion into memory for processing; identifying an existing digital signature block and an existing digital signature size block in a digitally signed file header of the digitally signed portion; obtaining a digital signature size value from the digital signature size block, the digital signature size value corresponding to the size of the digital signature block plus the length of an ancillary data block plus a pre-determined pad; authenticating the integrity of the digitally signed portion using the digital signature while processing the digital content; unwrapping a purchase mechanism built into as wrapper associated with the digital content; and extracting from the ancillary data block data referenced by instructions of the purchase mechanism, the extracting being performed without invalidating the digital signature.