Sumit Kumar Pandey

GIFT : A Small Present

In this article, we revisit the design strategy of PRESENT, leveraging all the advances provided by the research community in construction and cryptanalysis since its publication, to push the design up to its limits. We obtain an improved version, named GIFT, that provides a much increased efficiency in all domains (smaller and faster), while correcting the well-known weakness of PRESENT with regards to linear hulls.

Efficient window-based scalar multiplication on elliptic curves using double-base number system

In a recent paper [10], Mishra and Dimitrov have proposed a window-based Elliptic Curve (EC) scalar multiplication using double-base number representation. Their methods were rather heuristic. In this paper, given the window lengths w2 and w3 for the bases 2 and 3, we first show how to fix the number of windows, ρ, and then obtain a Double Base Number System (DBNS) representation of the scalar n suitable for window-based EC scalar multiplication. Using the DBNS representation, we obtain our first algorithm that uses a small table of precomputed EC points. We then modify this algorithm to obtain a faster algorithm by reducing the number of EC additions at the cost of storing a larger number of precomputed points in a table. Explicit constructions of the tables are also given.

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

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 weak existential unforgeable, IND-CCA2 secure in adaptive-predicates attack and achieves signer privacy. Secondly, 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 \(\mathcal{C}{t}\mathcal{E}\&\mathcal{S}\) 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.

On the direct construction of recursive MDS matrices

MDS matrices allow to build optimal linear diffusion layers in the design of block ciphers and hash functions. There has been a lot of study in designing efficient MDS matrices suitable for software and/or hardware implementations. In particular recursive MDS matrices are considered for resource constrained environments. Such matrices can be expressed as a power of simple companion matrices, i.e., an MDS matrix

Towards a general construction of recursive MDS diffusion layers

M = C_g^k

How to Leak a Secret and Reap the Rewards Too

M=Cgk for some companion matrix corresponding to a monic polynomial

Relaxing IND-CCA: indistinguishability against chosen ciphertext verification attack

g(X) \in \mathbb {F}_q[X]