Fully Invisible Protean Signatures Schemes.

Protean signatures (PSs), recently introduced by Krenn et al. (CANS `18), allow a semi-trusted third party (the sanitiser), to modify a signed message in a controlled way: the signer can define the message parts to be arbitrarily editable by the sanitiser, as well as message parts which can be redacted (but not altered otherwise) by the sanitiser. Thus, PSs generalise both redactable signatures (R...