We then propose a new efficient construction of fully functional convertible undeniable signature, which supports both selective conversion and universal conversion, and is immune to the claimability attacks. To the best of our knowledge, it is the most efficient convertible undeniable signature scheme with provable security in the standard model. A signature is comprised of three elements of a bilinear group. Both the selective converter of a signature and the universal converter consist of one group element only. Besides, the confirmation and disavowal protocols are also very simple and efficient. Furthermore, the scheme can be extended to support additional features which include the delegation of conversion and confirmation/disavowal, threshold conversion and etc.
We also propose an alternative generic construction of convertible undeniable signature schemes. Unlike the conventional sign-then-encrypt paradigm, the signer encrypts its (standard) signature with an identity-based encryption instead of a public key encryption. It enjoys the advantage of short selective converter, which is simply an identity-based user private key, and security against claimability attacks.Category / Keywords: public-key cryptography / convertible undeniable signature, standard model, signature scheme, strong Diffie-Hellman assumption, identity-based encryption Date: received 23 Oct 2009 Contact author: csqhuang at student cityu edu hk Available format(s): PDF | BibTeX Citation Version: 20091026:110612 (All versions of this report) Discussion forum: Show discussion | Start new discussion