3 research outputs found

    Lightweight Authenticated Encryption Mode Suitable for Threshold Implementation

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    This paper proposes tweakable block cipher (TBC) based modes PFB_Plus\mathsf{PFB\_Plus} and PFBω\mathsf{PFB}\omega that are efficient in threshold implementations (TI). Let tt be an algebraic degree of a target function, e.g.~t=1t=1 (resp.~t>1t>1) for linear (resp.~non-linear) function. The dd-th order TI encodes the internal state into dt+1d t + 1 shares. Hence, the area size increases proportionally to the number of shares. This implies that TBC based modes can be smaller than block cipher (BC) based modes in TI because TBC requires ss-bit block to ensure ss-bit security, e.g. \textsf{PFB} and \textsf{Romulus}, while BC requires 2s2s-bit block. However, even with those TBC based modes, the minimum we can reach is 3 shares of ss-bit state with t=2t=2 and the first-order TI (d=1d=1). Our first design PFB_Plus\mathsf{PFB\_Plus} aims to break the barrier of the 3s3s-bit state in TI. The block size of an underlying TBC is s/2s/2 bits and the output of TBC is linearly expanded to ss bits. This expanded state requires only 2 shares in the first-order TI, which makes the total state size 2.5s2.5s bits. We also provide rigorous security proof of PFB_Plus\mathsf{PFB\_Plus}. Our second design PFBω\mathsf{PFB}\omega further increases a parameter ω\omega: a ratio of the security level ss to the block size of an underlying TBC. We prove security of PFBω\mathsf{PFB}\omega for any ω\omega under some assumptions for an underlying TBC and for parameters used to update a state. Next, we show a concrete instantiation of PFB_Plus\mathsf{PFB\_Plus} for 128-bit security. It requires a TBC with 64-bit block, 128-bit key and 128-bit tweak, while no existing TBC can support it. We design a new TBC by extending \textsf{SKINNY} and provide basic security evaluation. Finally, we give hardware benchmarks of PFB_Plus\mathsf{PFB\_Plus} in the first-order TI to show that TI of PFB_Plus\mathsf{PFB\_Plus} is smaller than that of \textsf{PFB} by more than one thousand gates and is the smallest within the schemes having 128-bit security

    Understanding Cancer Progression Using Protein Interaction Networks

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