A system and method enable reliable tamper detection for printed
documents. Embodiments determine whether tampering has occurred and, if
detected, isolate it to a specific section, such as a single page of a
multi-page document. Embodiments render classes of documents tamper
evident with cryptographic level security, where such security was
previously unavailable, for example, documents printed using common
printers without special paper or ink. Embodiments enable proving the
date of document content without the need for expensive third party
archival, including documents held, since their creation, entirely in
secrecy or in untrustworthy environments, such as on easily-altered,
publicly-accessible internet sites. Embodiments can extend, by many
years, the useful life of currently-trusted integrity verification
algorithms, such as hash functions, even when applied to binary
executable files. Embodiments can efficiently identify whether multiple
document versions are substantially similar, even if they are not
identical, thus potentially reducing storage space requirements.