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Cryptographic device and an encoding device

  • US 10,567,158 B2
  • Filed: 10/10/2016
  • Issued: 02/18/2020
  • Est. Priority Date: 10/12/2015
  • Status: Active Grant
First Claim
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1. A cryptographic device arranged to compute (ƒ

  • K(M)) a key (K)-dependent cryptographic function (ƒ

    ) for an input message (M), the cryptographic device comprisinga data store arranged to store multiple variables (w) on which the cryptographic device acts to compute the cryptographic function, a table store storing multiple look-up tables, the multiple look-up tables together forming a table network implementing the cryptographic function, and a control unit configured to apply the cryptographic function to the input message by applying the multiple look-up tables to the variables represented in the data store, characterized in thata variable (w) is distributed over multiple shares (wj) and represented in the data store as multiple encoded shares (xj), an encoded share being an encoding (xj=Encj(wj,sj) of a share (wj) together with a state (sj), the multiple states (sj) corresponding to the same variable (w) having a relationship with the input message (M) so that there exists an injective mapping (Σ

    ) from the input message (M) to the multiple states (Σ

    (M)=s0, . . . , sn−

    1
    )), anda look-up table takes as input one or more encoded shares of one or more variables, the table network performing operations on the multiple shares (wj) of the encoded variable (W) and simultaneously performing redundant operations on the multiple states (sj) maintaining an injective mapping from the input message (M) to the multiple states.

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