Thales Dis France Sa

Gemalto Sa

Thales Dis France Sas

Mariya Georgieva

Aline Gouget

Frederic De Portzamparc

Decryption of an RSA encrypted message encrypted with a public RSA key by receiving encrypted key share components computed by generating a private RSA key d and a RSA modulus integer N, where N and d are integers; splitting the private key into key shares, encrypting with a fully homomorphic encryption (FHE) algorithm each key share component by using a Fully Homomorphic Encryption secret key ps associated with a set Ss to generate the encrypted key share components of said secure RSA key, computing an intermediate value YS for each set SS from said encrypted key share components, such that said computed intermediate value is a part of the RSA decrypted message, under FHE-encrypted form, and decrypting the encrypted message by combining said computed intermediate values for all sets.

Method of RSA signature or decryption protected using a homomorphic encryption

Secure computation of a random number sequence in a cryptographic device. The computation is secured by receiving a homomorphic ciphertext seed vector, selecting an initial internal state from the seed vector, the initial internal state composed of a subset of elements of the seed vector, updating an internal state from a previous internal state using multivariate functions accepting elements of the previous internal state as inputs to produce a homomorphic ciphertext from homomorphic ciphertext input values, generating an intermediate result vector of homomorphic ciphertexts from the homomorphic ciphertext internal state multivariate functions accepting the elements of the internal state as inputs to produce a homomorphic ciphertext from homomorphic ciphertext input values, and decrypting the intermediate result vector elements into plaintext vector elements, thereby producing a plaintext deterministic random sequence vector corresponding to plaintext seed elements used to produce the seed vector. Other systems and methods are disclosed.

Cryptography device having secure provision of random number sequences

The present invention relates to a method of generating a secure RSA key by a server comprising the steps of: &#x2022;generating (S) a private RSA key d and a RSA modulus integer N; &#x2022;splitting (S) the secret key integer d in j key shares dof length n, with j in [1, J], J being an integer, and such that d=d+d+ . . . +dmod phi(N), with each key share dbeing equal to (d. . . d. . . d) with each key share component djin {0 . . . 2{circumflex over (&#x2003;)}b&#x2212;1} and i in [0, n/b&#x2212;1], b being an integer inferior to n and phi the Euler's totient function; &#x2022;encrypting (S) with a fully homomorphic encryption (FHE) algorithm each key share component dof the private RSA key d by using a Fully Homomorphic Encryption secret key pof a set Scomprising the index couple (i,j), to generate an encrypted key share component edof said secure RSA key, said set Sbeing a set of integer couples, among a predetermined integer number u of disjoint sets {S, SS, S, . . . S} generated such that: U{S}={(i,j) such that i in [0, n/b&#x2212;1], j in [1, J]} and each said set among {S, . . . S} being associated with a Fully Homomorphic Encryption (FHE) secret key.

Secure cryptography operations on a white-box cryptography device. Receiving a first message. Receiving a cryptographic key encrypted using a homomorphic encryption scheme. Performing a cryptographic operation, e.g., decryption or digital signature, using the encrypted cryptographic key. Performing a homorphically encrypted tracer calculation that traces the performance of the cryptography operations on the white-box cryptography device thereby allowing verification that all steps of the cryptography operation has been performed without external manipulation. Performing a key-exchange operation. Decrypting the key-exchange output using an alternate cryptographic key stored on the cryptographic device.

Cryptography device having improved security against side-channel attacks

A method for operating an attribute assertion device having a processor and memory to create an unlinkable digital signature-equivalent of an assertion message that is verifiable&#x2014;by a service provider receiving the unlinkable digital signature-equivalent&#x2014;as being generated from a digital signature of a known attribute provider having a public key PK. Operating the processor of the attribute assertion device to transform a digital signature of the attribute message into an unlinkable digital signature-equivalent using a one-way transformation of the signature, with the transformation process using a random value generated by the attribute assertion device and a challenge provided by the service provider.

Secure electronic device with mechanism to provide unlinkable attribute assertion verifiable by a service provider

A system, method and computer-readable storage medium for decrypting a code c using a modified Extended Euclidean Algorithm (EEA) having an iteration loop independent of the Hamming weight of inputs to the EEA and performing a fixed number of operations regardless of the inputs to the EEA thereby protecting a cryptographic device performing the decryption from side-channel attacks.

System and method for providing defence to a cryptographic device against side-channel attacks targeting the extended euclidean algorithm during decryption operations

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Meudon, France

Mariya Georgieva