Motivations for a theoretical approach to WYSIWYS

The statement “What You See Is What You Sign” (WYSIWYS) expresses a functional requirement for digital signatures of electronic documents, in particular when considering legally binding signatures. However this statement is intrinsically wrong. In fact a signer never really sees what he digitally signs, namely the bits of the electronic document, but he sees only one of the possible representations of these bits. This is due to the theory and the technology underlying the actual implementations of the digital signatures. Moreover, while the acronym refers only to the presentation on the signer side, in legal settings the presentation on the recipient side must be also taken into account as well as the relation between the twos.