What's the problem? If the signature is removed so is the authenticity; it's as if it were saved unsigned (and hence unauthenticated)?
I work in an industry where once something is signed, it cannot become un-signed. If we wish to remove authentication of an approval, we have very strict rules.
The point is that this is trivial to achieve for anyone, even if the file is locked after signing.
They just need to keep a copy of the unsigned file, delete the signed one, and replace it with the unsigned file. So such protection means nothing.
Repudiating signatures is a very bad thing, but it can only have real meaning if someone or some process knew about the signing. Otherwise, it's like someone signing a piece of paper, and destroying their signed copy without showing it to anyone; it's as if it never happened, and nothing was gained. If on the other hand a person has received the signed file, or a process has securely archived it, then removing a signature has no repudiating effect on the copy.
It can be hard to convert paper-based to electronic-based workflows where files can be freely duplicated, shared etc.
Clearly, though, if a person can sign a file, then others can act on that signature, and then the signer can still edit the original signed file, there is a big problem, not just of repudiation but of auditability.
Hi Screen name,
I'm aware of the surrounding issues and can only take appropriate control steps to prevent files being overwritten.
Still, my question remains:
Can I prevent the owner of a signature from clearing their signature once applied?
Acrobat XI shows in the signature panel deleted signatures. So, if you delete your own signature, there is now a record in the Acrobat/Reader UI and you superiors will call you on the carpet.