A variety of systems responsive to watermarked documents are detailed. In
one, watermarking is employed to facilitate secure online transactions.
In another, a system for exchanging data is provided. One system includes
a user terminal and a central site. The user terminal includes a
watermark reader, and a capture device to capture an image of a
watermarked document. The central site includes a database of image
hashes. The user terminal communicates with the central site. The
watermark reader reads a watermark and computes a hash of a captured
image, and passes the hash to the central site for comparison with the
database of image hashes.