This note considers 'security paper' and other mechanisms to protect the integrity of documents.

It supplements other pages on forgery and identity crime.

It covers -

• introduction
• traditional techniques
• recent innovations
• studies

     introduction

Public and private sector organisations that rely on documents as tokens of identity (eg passports and academic testamurs) or for commercial transactions (eg share certificates, bonds, cheque books, lottery tickets and banknotes) have used what is often referred to as security paper or security printing in order to protect the integrity of those documents.

Such documents typically have special physical characteristics (involving the paper stock and/or any printing) that are meant to -

• signal that a printed or handwritten inscription (eg a stamp or signature) has been altered or illicitly added
• readily differentiate the document from a copy (eg allow a bank teller to determine that a banknote is counterfeit because the paper looks different)

Soome of those characteristics may be identifiable on cursory examination by a non-specialist. Others might require detailed forensic analysis. Such analysis often takes place once suspicion has been aroused, eg because the bearer's behaviour is anomalous or there is a typographical error on a document that otherwise seems genuine.

The 'authority' of security paper is predicated on several assumptions. Those assumptions are that issuers of the documents will -

• control access to paper stocks (eg counterfeiters will not be able to buy special banknote paper)
• safeguard the production of documents that feature security paper (eg will not allow printers to make extra unauthorised copies of a particular document using legitimate paper and ink)
• control the distribution of the documents (eg prevent their staff from providing blank passports to an associate and ensure that blank passports are not lost or stolen
• maintain an appropriate document verification regime, with for example registration of document bearers and/or documents (such as a unique numbering scheme), routine checking by representatives who encounter the documents and access to forensic analysis when a document's legitimacy is called into question.

As those points (and the discussion elsewhere on this site regarding identity crime and forgery indicate) security paper is a tool rather than an outcome.

There have for example been instances where criminals have persuaded officials to provide them with an 'authentic' passport, using a bribe, sexual or other coercion, or simply providing what appear to be legitimate 'breeder' documents such as birth and marriage certificates. Others have relied on stolen/lost blank passports, illicitly adding details to what would otherwise be forensically-credible documents (eg because those documents feature the proper paper and printing). Others have taken legitimate cheques, illicitly altering the payee and amount details (eg the authorised payment of $500 to you becomes - hey presto - a payment of $50,000 to me).

Reliance on security documents reflects notions of need and risk, in particular the balance between the potential gains from misuse of the document (eg a counterfeit banknote) and the cost of prevention.

Passports thus have a greater significance than bus tickets and are therefore meant to be harder to forge; unlike bus tickets they typically feature security paper. Some documents, such as lottery tickets, embody substantial anonymity (eg there is no requirement for registration and verification may be difficult). Other documents are tied to large scale registration systems, with for example unique numbering drawn from a central register and the potential for verification through comparison of the document with copies of a signature and photograph in that register).

     traditional techniques

As the preceding paragraphs suggest, the authenticity and/or integrity of particular documents (eg that they indeed came from the purported issuer and have not been illicitly altered) has traditionally relied on the 'raw material' of the document and how it is processed, in particular its printing.

Issuers have often used paper with special attributes such as a unique watermark (visible with the naked eye or with the aid of a lens) or material not found in ordinary paper (eg expensive fibre and high production standards that distinguish a banknote from the lower quality paper used in books and newspapers). Such use was important when papermaking was an art and production was typically small-scale.

Industrialisation increasingly saw reliance on printing techniques, predicated on a recognition that the production of high-quality printing plates was expensive (involved skill and time) and that printing using those plates involved expertise, precision presses and quality control that would exclude most amateurs.

     studies

Among other works see K J Schell's 'History of Document Security' in Karl de Leeuw & Jan Bergstra [ed] The History of Information Security: A Comprehensive Handbook (Amsterdam: Elsevier 2007) 197-242. Pointers to works on paper, on watermarking and printing press technologies are provided in the print profile elsewhere on this site.