International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 15 June 2015

Tapas Pandit, Sumit Kumar Pandey, Rana Barua
ePrint Report ePrint Report
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.

Expand

Additional news items may be found on the IACR news page.