## Cryptology ePrint Archive: Report 2015/555

Attribute-Based Signcryption : Signer Privacy, Strong Unforgeability and IND-CCA2 Security in Adaptive-Predicates Attack

Tapas Pandit and Sumit Kumar Pandey and Rana Barua

Abstract: An Attribute-Based Signcryption (ABSC) is a natural extension of Attribute-Based Encryption (ABE) and Attribute-Based Signature (ABS), where we have the message confidentiality and authenticity together. Since the signer privacy is captured in security of ABS, it is quite natural to expect that the signer privacy will also be preserved in ABSC. In this paper, first we propose an ABSC scheme which is \textit{weak existential unforgeable, IND-CCA2} secure in \textit{adaptive-predicates} attack and achieves \textit{signer privacy}. Secondly, by applying strongly unforgeable one-time signature (OTS), the above scheme is lifted to an ABSC scheme to attain \textit{strong existential unforgeability} in \textit{adaptive-predicates} model. Both the ABSC schemes are constructed on common setup, i.e the public parameters and key are same for both the encryption and signature modules. Our first construction is in the flavor of $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$ paradigm, except one extra component that will be computed using both signature components and ciphertext components. The second proposed construction follows a new paradigm (extension of $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$), we call it Commit then Encrypt and Sign then Sign" ($\mathcal{C}{t}\mathcal{E}\&\mathcal{S}{t}\mathcal{S}$). The last signature is done using a strong OTS scheme. Since the non-repudiation is achieved by $\mathcal{C}{t}\mathcal{E}\&\mathcal{S}$ paradigm, our systems also achieve the same.

Category / Keywords: public-key cryptography / Attribute-based encryption, Attribute-based signature, Attribute-based signcryption, Commitment scheme.

Original Publication (with major differences): Proceedings of 8th International Conference, ProvSec 2014, LNCS 8783, pp. 274-290, Springer.
DOI:
10.1007/978-3-319-12475-9_19

Date: received 5 Jun 2015, last revised 15 Jun 2015

Contact author: tapasgmmath at gmail com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2015/555

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