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(11)    Patent No :    AP 1969   
(21)    Application No :    AP/P/2005/003445   
(22)    Filing Date :    19.05.2004   
(24)    Date of Grant &    11.03.2009   
(45)    Publication :

(30)  Priority Data       
(33) Country    (31) Number    (32) Date
EP    0301169606    23.05.2003

(85)    Designated State

BW    GM    GH    KE    LS    MW  MZ   NA   SL
SD    SZ    T Z    UG    ZM    ZW
(73) Applicant(s)

NAGRAVISION S. A., Route de Geneve,22, CH-1033 Cheseaux-sur-Lusanne,

(72) Inventors

JUNOD Pascal, Switzerland

VAUDENAY Serge, Switzerland

(74) Representative

(51)    International  Classification   H04L 9/06 (2006.01)

(54)    Title

Device and method for encrypting and decrypting a block of data

(57)    Abstract

Method to encrypt or decrypt blocks of data X to Y, based on a main key R, this method using several serially connected modules, each module using a sub-key RA derived from the main key R and comprising the steps of: - inputting at least two initial values XOL and XOR, and mixing these values to form a mixed value XI, - obtaining a value X2 by mixing a first part RAH of the

sub-key RA with the value XI, - obtaining a value X3 by applying the value X2 to a substitution layer, comprising at least one substitution box (sbox), - obtaining a value X4 by using a diffusion box of multi-permutation type based on the value X3, - obtaining a value X5 by mixing a second part RAL of the sub-key RA with the value X4, - obtaining the value X6 by applying to the value X5 a substitution layer, - obtaining a value X7 by mixing a first part RAH

of the sub-key RA with the value X6, - mixing the value X7 with the initial at least two values XOL and XOR to obtain the at least two values X8L and X81R, X8L and X8R representing the output value X8 of the module. This method using at least two modules, and applies to at least one of the value

(56)    Documents Cited :    EP 0 482 154 A   EP 0 221 538 A   US 5 675 653 A


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