Paper 2013/130

Blank Digital Signatures

Christian Hanser and Daniel Slamanig


In this paper we present a novel type of digital signatures, which we call blank digital signatures. The basic idea behind this scheme is that an originator can define and sign a message template, describing fixed parts of a message as well as multiple choices for exchangeable parts of a message. One may think of a form with blank fields, where for such fields the originator specifies all the allowed strings to choose from. Then, a proxy is given the power to sign an instantiation of the template signed by the originator by using some secret information. By an instantiation, the proxy commits to one allowed choice per blank field in the template. The resulting message signature can be publicly verified under the originator's and the proxy's signature verification keys. Thereby, no verifying party except the originator and the proxy learn anything about the ``unused'' choices from the message template given a message signature. Consequently, the template is hidden from verifiers. We discuss several applications, provide a formal definition of blank digital signature schemes and introduce a security model. Furthermore, we provide an efficient construction of such a blank digital signature scheme from any secure digital signature scheme, pairing-friendly elliptic curves and polynomial commitments, which we prove secure in our model. We also provide a detailed efficiency analysis of our proposed construction supporting its practicality. Finally, we outline several open issues and extensions for future work.

Note: minor changes (typos ...)

Available format(s)
Public-key cryptography
Publication info
Published elsewhere. major revision of the ASIACCS'13 paper
Digital signature schemeblank digital signatureselliptic curvespairingspolynomial commitments
Contact author(s)
christian hanser @ iaik tugraz at
2013-12-11: last of 15 revisions
2013-03-07: received
See all versions
Short URL
Creative Commons Attribution


      author = {Christian Hanser and Daniel Slamanig},
      title = {Blank Digital Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 2013/130},
      year = {2013},
      note = {\url{}},
      url = {}
Note: In order to protect the privacy of readers, does not use cookies or embedded third party content.