Authenticating printed paper documents and websites against a blockchain record

Abstract

A system and method are disclosed for rendering published documents tamper evident. Embodiments render classes of documents tamper evident with cryptographic level security or detect tampering events, where such security was previously unavailable, for example, in 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 use a document's prior registration date in a blockchain to establish a no-later-than date-of-existence for that document. Embodiments can extend the useful life of 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.