Abstract
In this paper we propose a new authentication and localisation scheme to produce a watermark which can be embedded in a limited capacity binary text document and that will work in a print and scan environment. The scheme utilises Message Authentication Codes (MAC), specifically OMACs, which create a cryptographic fixed-length summary of a document. An OMAC must be truncated to a form part of our watermark and is used during authentication. The remainder of the watermark is used during localisation. We have created over 2,000,000 watermarks in controlled experiments to evaluate their ability to authenticate a document and localise any changes. In addition, we have embedded an authenticating watermark into seven different documents and authenticated them after printing and scanning.