Lightweight Diffusion Layer from the kthk^{th} root of the MDS Matrix

The Maximum Distance Separable (MDS) mapping, used in cryptography deploys complex Galois field multiplications, which consume lots of area in hardware, making it a costly primitive for lightweight cryptography. Recently in lightweight hash function: PHOTON, a matrix denoted as ‘Serial’, which required less area for multiplication, has been multiplied 4 times to achieve a lightweight MDS mapping. But no efficient method has been proposed so far to synthesize such a serial matrix or to find the required number of repetitive multiplications needed to be performed for a given MDS mapping. In this paper, first we provide an generic algorithm to find out a low-cost matrix, which can be multiplied k times to obtain a given MDS mapping. Further, we optimize the algorithm for using in cryptography and show an explicit case study on the MDS mapping of the hash function PHOTON to obtain the ‘Serial’. The work also presents quite a few results which may be interesting for lightweight implementation

Lithiated Tin di-sulfide micro-flowers with expanded interlayer spaces coupled with bakelite-carbon for an enhanced performance supercapacitor

Lithiated SnS2 (LiSnS2) is a highly promising supercapacitor electrode owing to the wide interlayer spaces in its crystal structure and the large effective surface area, afforded by its nanostructure. Here, LiSnS2 micro-flowers with a nominal conductivity of ∼0.4 μS cm−1 are directly prepared for the first time, by solid-sate diffusion, with a 2D layered rhombohedral pre-lithiated structure, affording facile intercalation of electrolyte cations in an asymmetric supercapacitor, with Bakelite sourced porous carbon (BSPC) as the anode. Significant enhancement in the storage performance by mixing LiSnS2 with BSPC in 3:1 (High) and 1.66:1 (Low) weight ratios, with the High LiSnS2 cell encompassing an aqueous electrolyte delivering a specific capacitance (SC) of 249 F g−1 at current density of 1 A g−1, Emax and Pmax of 34 Wh kg−1 and 3.5 kW kg−1, and enduring 10,000 cycles, with 88% SC retention, over a potential window of 1.4 V. Both diffusive and capacitive contributions account for this performance with the ability of short diffusion path lengths of the sulfide, and the large electrical conductivity of BSPC imparting a fast kinetic response to the cell. A non-aqueous High LiSnS2 supercapacitor, could be charged to a high voltage of 2.7 V, with a SC of 32 F g−1, thus ratifying the suitability of this cell for practical applications. This work opens up the possibility of developing a variety of previously difficult to synthesize pre-lithiated metal chalcogenides or oxides, for such materials are more conducive for undergoing reversible ion-intercalation/de-intercalation contrasting with their non-lithiated analogues and have the potential to give a tremendous boost to their energy storage performances. © 2021 Elsevier Lt