Editing Digital signature (section)

===WYSIWYS===
{{Main|WYSIWYS}}
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)<ref name="WYSIWYS_SeminalPaper">{{cite journal|last1=Landrock|first1=Peter|last2=Pedersen|first2=Torben|title=WYSIWYS? – What you see is what you sign?|journal=Information Security Technical Report|date=1998|volume=3|issue=2|pages=55–61|doi=10.1016/S0167-4048(98)80005-8}}</ref> 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 [[Cryptomathic|Torben Pedersen]] to describe some of the principles in delivering secure and legally binding digital signatures for Pan-European projects.<ref name="WYSIWYS_SeminalPaper" />