Signature-embedding in printed documents for security and forensic applications

Despitetheincreaseinemailandotherformsofdigitalcommunication,theuseofprinteddocumentscontinues to increase every year. Many types of printed documents need to be \secure" or traceable to the printer that was used to print them. Examples of these include identity documents (e.g. passports) and documents used to commit a crime. Traditional protection methods such as special inks, security threads, or holograms, can be costprohibitive. Thegoalsofourworkaretosecurelyprintandtracedocumentsonlowcostconsumerprinters suchasinkjetandelectrophotographic(laser)printers. Wewillaccomplishthisthroughtheuseofintrinsicand extrinsic features obtained from modelling the printing process. Speciflcally we show that the banding artifact intheEPprintprocesscanbeviewedasanintrinsicfeatureoftheprinterusedtoidentifyboththemodeland make of the device. Methods for measuring and extracting the banding signals from documents are presented. The use of banding as an extrinsic feature is also explored. Keywords: document security, secureprinting, printer identiflcation, banding