A system authenticates an original hardcopy document using a digital
signature generation system and a digital signature verification system.
Initially, the original hardcopy document is scanned to provide a bitmap
image to the signature generation system. The bitmap image is highly
compressed by the signature generation system using compression schemes
such as MPEG (for gray images) or a low-fidelity symbol based compression
scheme (for bi-level images). A signed hardcopy document is then printed
that includes the bitmap image and an authentication token. The
authentication token is encoded in the signed hardcopy document using
either serpentine halftone patterns or data glyphs. The authenticity of
the signed hardcopy document is verified by inputting a scanned bitmap
image of the signed hardcopy document into the signature verification
system. Once received, the signature verification system decodes,
authenticates, and decompresses the bitmap image to define decompressed
image data. The decompressed image data is then output to a display or
printer and compared with the signed hardcopy document to determine
whether it is authentic.