Volume 6 - Issue 3
Attribute-Based Signcryption: Signer Privacy, Strong Unforgeability and IND-CCA Security in Adaptive-Predicates Model (Extended Version)
- Tapas Pandit
Stat-Math Unit, Indian Statistical Institute, Kolkata, India
tapasgmmath@gmail.com
- Sumit Kumar Pandey
School of Physical and Mathematical Sciences Nanyang Technological University, Singapore
emailpandey@gmail.com
- Rana Barua
Stat-Math Unit, Indian Statistical Institute, Kolkata, India
ranabarua.isi@gmail.com
Keywords: Attribute-based encryption, Attribute-based signature, Attribute-based signcryption
Abstract
Attribute-Based Signcryption (ABSC) is a natural extension of Attribute-Based Encryption (ABE)
and Attribute-Based Signature (ABS), where one can 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 weak existential unforgeable and IND-CCA secure in adaptive-predicates
models and, achieves signer privacy. Then, by applying strongly unforgeable one-time signature
(OTS), the above scheme is lifted to an ABSC scheme to attain strong existential unforgeability
in 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 CtE&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 CtE&S), we call it “Commit then Encrypt and
Sign then Sign” (CtE&StS). The last signature is generated using a strong OTS scheme. Since,
the non-repudiation is achieved by CtE&S paradigm, our systems also achieve the same.