Paper 2019/039

Fully Invisible Protean Signatures Schemes

Stephan Krenn, Henrich C. Pöhls, Kai Samelin, and Daniel Slamanig


Protean Signatures (PS), recently introduced by Krenn et al. (CANS '18), allow a semi-trusted third party, named the sanitizer, to modify a signed message in a controlled way. The sanitizer can edit signer-chosen parts to arbitrary bitstrings, while the sanitizer can also redact admissible parts, which are also chosen by the signer. Thus, PSs generalize both redactable signature (RSS) and sanitizable signature (SSS) into a single notion. However, the current definition of invisibility does not prohibit that an outsider can decide which parts of a message are redactable - only which parts can be edited are hidden. This negatively impacts on the privacy guarantees provided by the state-of-the-art definition. We extend PSs to be fully invisible. This strengthened notion guarantees that an outsider can neither decide which parts of a message can be edited nor which parts can be redacted. To achieve our goal, we introduce the new notions of Invisible RSSs and Invisible Non-Accountable SSSs (SSS'), along with a consolidated framework for aggregate signatures. Using those building blocks, our resulting construction is significantly more efficient than the original scheme by Krenn et al., which we demonstrate in a prototypical implementation.

Note: We have fixed some details based on the reviewers' comments along with some inconsistencies.

Available format(s)
Public-key cryptography
Publication info
Preprint. MINOR revision.
sanitizable signaturesprotean signaturesredactable signaturesprivacyimplementationpublic-key cryptography
Contact author(s)
stephan krenn @ ait ac at
daniel slamanig @ ait ac at
hp @ sec uni-passau de
kaispapers @ gmail com
2020-04-09: revised
2019-01-17: received
See all versions
Short URL
Creative Commons Attribution


      author = {Stephan Krenn and Henrich C.  Pöhls and Kai Samelin and Daniel Slamanig},
      title = {Fully Invisible Protean Signatures Schemes},
      howpublished = {Cryptology ePrint Archive, Paper 2019/039},
      year = {2019},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.