Technically speaking, a digital signature applies to a string of bits, whereas humans and applications "believe" that they sign the semantic interpretation of those bits. In order to be semantically interpreted, the bit string must be transformed into a form that is meaningful for humans and applications, and this is done through a combination of hardware and software based processes on a computer system. The problem is that the semantic interpretation of bits can change as a function of the processes used to transform the bits into semantic content. It is relatively easy to change the interpretation of a digital document by implementing changes on the computer system where the document is being processed. From a semantic perspective this creates uncertainty about what exactly has been signed. WYSIWYS (What You See Is What You Sign) means that the semantic interpretation of a signed message cannot be changed. In particular this also means that a message cannot contain hidden information that the signer is unaware of, and that can be revealed after the signature has been applied. WYSIWYS is a requirement for the validity of digital signatures, but this requirement is difficult to guarantee because of the increasing complexity of modern computer systems. The term WYSIWYS was coined by Peter Landrock and Torben Pedersen to describe some of the principles in delivering secure and legally binding digital signatures for Pan-European projects.
Technically speaking a digital signature applies to a string of bits whereas humans and applications "believe" that they sign the semantic interpretation of those bits In order to be semantically interpreted the bit string must be transformed into a form that is meaningful for humans and applications and this is done through a combination of hardware and software based processes on a computer system The problem is that the semantic interpretation of bits can change as a function of the processes used to transform the bits into semantic content It is relatively easy to change the interpretation of a digital document by implementing changes on the computer system where the document is being processed From a semantic perspective this creates uncertainty about what exactly has been signed WYSIWYS (What You See Is What You Sign) means that the semantic interpretation of a signed message cannot be changed In particular this also means that a message cannot contain hidden information that the signer is unaware of and that can be revealed after the signature has been applied WYSIWYS is a requirement for the validity of digital signatures but this requirement is difficult to guarantee because of the increasing complexity of modern computer systems The term WYSIWYS was coined by Peter Landrock and Torben Pedersen to describe some of the principles in delivering secure and legally binding digital signatures for Pan-European projects