Abstract: A method for protecting a calculation, by an electronic circuit, of a modular exponentiation of a digital quantity, wherein: a first variable is initialized with a random quantity; at least one second variable is initialized with a value which is a function of the digital quantity; at least for a bit at 1 of an exponent of the modular exponentiation, the first variable is updated by: a) the quotient of its content and a power of the random quantity; and b) the product of its content by that of the second variable; and once all the exponent bits have been processed, the content of the first variable is divided by the random quantity to provide the result of the modular exponentiation.

Abstract: A method of detecting a fault attack including generating a first signature of a first group of data values by performing a single commutative non-Boolean arithmetic operation between all the data values of the first group; generating a second set of data values by performing a permutation of the first set of data values; generating a second signature of the second group of data values by performing said single commutative non-Boolean arithmetic operation between all the data values of the second group; and comparing the first and second signatures to detect a fault attack.

Abstract: The invention concerns a method of detecting a fault attack including providing a plurality of blinding values; generating a first set of data elements including a first group of data elements and at least one additional data element generated by performing the exclusive OR between at least one data element in the first group and at least one of the blinding values; generating a second set of data elements corresponding to the exclusive OR between each data element of the first set and a selected one of the plurality of blinding values; generating a first signature by performing a commutative operation between each of the data elements of the first set; generating a second signature by performing the commutative operation between each of the data elements of the second set; and comparing the first and second signatures to detect a fault attack.

Abstract: A method of protecting a circuit from attacks aiming to discover secret data used during the execution of a cryptographic calculation by the circuit, by, executing a transformation calculation implementing a bijective transformation function, receiving as input a secret data, and supplying a transformed data, executing a cryptographic calculation receiving as input a data to process and the transformed data, and executing an inverse transformation calculation receiving as input the result of the cryptographic calculation, and supplying a result that the cryptographic calculation would have supplied if it had been applied to the data to process and directly to the secret data, the data to process belong to a stream of a multiplicity of data, the transformed data being supplied as input to the cryptographic calculation for all the data of the stream.

Abstract: A method of protecting a circuit from attacks aiming to discover secret data used during the execution of a cryptographic calculation by the circuit, by, executing a transformation calculation implementing a bijective transformation function, receiving as input a secret data, and supplying a transformed data, executing a cryptographic calculation receiving as input a data to process and the transformed data, and executing an inverse transformation calculation receiving as input the result of the cryptographic calculation, and supplying a result that the cryptographic calculation would have supplied if it had been applied to the data to process and directly to the secret data, the data to process belong to a stream of a multiplicity of data, the transformed data being supplied as input to the cryptographic calculation for all the data of the stream.

Abstract: A method and a circuit for masking a digital word by application of a random bijection, including applying at least one first operation including selecting a non-disjoint subset of the word having its position and size depending on a first random quantity, and assigning to each bit of the subset, the state of the bit having a symmetrical position with respect to the middle of the subset, to obtain a masked digital quantity.

Abstract: A method and a circuit for protecting a digital quantity over a first number of bits, in an algorithm executing at least one modular exponentiation of data by the quantity, the steps including at least one squaring up and at least one multiplication and implementing, for each bit of the quantity, different calculation steps according to the state of the bit, a same number of multiplications being performed whatever the state of the bit and all the calculation steps using a multiplication being taken into account to calculate a final result.

Abstract: A method and a circuit for ciphering or deciphering data with a key by using at least one variable stored in a storage element and updated by the successive operations, the variable being masked by at least one first random mask applied before use of the key, then unmasked by at least one second mask applied after use of the key, at least one of the masks being dividable into several portions successively applied to the variable and which, when combined, represent the other mask.

Abstract: A method for protecting the execution of a ciphering or deciphering algorithm against the introduction of a disturbance in a step implementing one or several first values obtained from second values supposed to be invariant and stored in a non-volatile memory in which, during an execution of the algorithm: a current signature of the first values is calculated; this current signature is combined with a reference signature previously stored in a non-volatile memory; and the result of this combination is taken into account at least in the step of the algorithm implementing said first values.

Abstract: A method for protecting the integrity of data ciphered by a ciphering algorithm providing at least an intermediary state meant to be identical in ciphering and in deciphering, this intermediary state being sampled during the ciphering to generate a signature.

Abstract: A method and a circuit for detecting a loss in the equiprobable character of a first output bit flow originating from at least one first element of normalization of an initial bit flow, including analyzing the flow rate of the normalization element.

Abstract: A method for determining the entropy of a noise source providing a bit flow, a method and a device for generating a bit flow, including parallelizing the bit flow to obtain first words over a first number of bits, applying to the successive words a compression function, and evaluating a second number of bits over which the compression function provides its results, the second number representing the number of useful bits in the first words.

Abstract: A method and a circuit for scrambling an RSA-CRT algorithm calculation by an electronic circuit, in which a result is obtained from two modular exponentiation calculations, each providing a partial result, and from a recombination step, and in which a first step adds a digital quantity to at least one first partial result before said recombination step; and a second step cancels the effects of this quantity after the recombination step.

Abstract: A method for protecting a calculation, by an electronic circuit, of a modular exponentiation of a digital quantity, wherein: a first variable is initialized with a random quantity; at least one second variable is initialized with a value which is a function of the digital quantity; at least for a bit at 1 of an exponent of the modular exponentiation, the first variable is updated by: a) the quotient of its content and a power of the random quantity; and b) the product of its content by that of the second variable; and once all the exponent bits have been processed, the content of the first variable is divided by the random quantity to provide the result of the modular exponentiation.

Abstract: A method for protecting a calculation on an elliptic curve, by an electronic circuit, wherein a point of an elliptic curve is multiplied by a digital quantity, comprising the steps of: initializing a first variable with a value which is a function of a random quantity; initializing at least a second variable with a value which is a function of the digital quantity; at least for a bit at 1 of the digital quantity, the first variable is updated by: a) subtracting a multiple of the random quantity; and b) adding the content of the second variable; and once all the bits of the digital quantity have been processed, subtracting from the first variable the product of the point to by the random quantity to provide the result.

Abstract: A method for protecting a calculation, by an electronic circuit, of a modular exponentiation of a digital quantity, wherein: a first variable is initialized with a random quantity increased by once unit; a second variable is initialized with the product of the digital quantity by the random quantity; a third variable is initialized with the digital quantity; iteratively for all the bits at 1 of an exponent of the modular exponentiation, the first variable is updated by: a) multiplying its content by that of the third variable; and b) subtracting thereto the content of the second variable increased by the random quantity; and once all the bits of the exponent have been processed, the content of the first variable is decreased by the random quantity to provide the result of the modular exponentiation.

Abstract: A method for protecting a volatile memory against a virus, wherein: rights of writing, reading, or execution are assigned to certain areas of the memory; and a first list of opcodes authorized or forbidden as a content of the areas is associated with each of these areas.

Abstract: A method for protecting a volatile memory against a virus, wherein: rights of writing, reading, or execution are assigned to certain areas of the memory; and a first list of opcodes for which the access to the areas is authorized or forbidden is associated with each of these areas.

Abstract: The protected method of cryptographic computation includes N computation rounds successively performed to produce an output data from an input data and a private key. The method also includes a first masking stage to mask the input data, so that each intermediate data used or produced by a computation round is masked, and a second masking stage to mask data manipulated inside each computation round.

Abstract: A method for controlling the execution of a program implementing successive operations, including, during program execution, comparing each operation with a pre-established list, and for each operation contained in the list, incrementing and memorizing a number of occurrences of this operation; and at the end of the program execution, comparing the number of occurrences of the current program execution for each operation with previously-stored ranges of numbers of occurrences assigned to each operation.