Visual Representation of Advanced Electronic Signatures

Abstract

This paper considers the issues concerning the visual representation of cryptographic based digital signatures (referred to as advanced electronic signatures in the European legal context). Two particular aspects are considered: firstly the visual appearance of the signature as part of the document as applied by the signatory at time of signing, secondly the representation of the digital signature when verified by the recipient. The paper proposes principles for these two aspects of visual representation to ensure that the normal user of electronic documents, who has little or no knowledge of digital signature technology, can best understand the signature whilst enabling forensic experts to investigate the details of the signature in case of dispute over a signed document. The paper also touches on a further aspect of signature representation, which is still the subject to ongoing debate. This paper is based on work carried out in ETSI on standards for visual representation of advanced electronic signatures in PDF with input from European projects using signed documents (see acknowledgements at end of paper).