Abstract: An electronic apparatus includes a communication apparatus communicating with an external apparatus, a memory storing a message, and a processor generating a digital signature for the message, wherein the processor generates a first signature ciphertext and a message ciphertext by encrypting each of first signature information and the message by using a homomorphic encryption public key, obtains encrypted third signature information generated using second signature information, an element value corresponding to the second signature information, the first signature ciphertext, and the message ciphertext, and calculates a first digital signature value included in the digital signature by using the first signature information and the second signature information, calculate a second digital signature value included in the digital signature by decrypting the encrypted third signature information, and generate the digital signature by using the calculated first digital signature value and second digital signature v

Abstract: In a method of generating a secret key according to an embodiment, a share of each of a user and a plurality of other users for a secret key of the user are generated, the share of each of the plurality of other users is provided to a user terminal of each of the plurality of other users, a share of the user for a secret key of each of the plurality of other users is received from the user terminal of each of the plurality of other users, and a new secret key of the user is generated using the share of the user for the secret key of the user and the shares of the user for the secret key of each of the plurality of other users.

Abstract: An electronic device is disclosed. The electronic device includes a memory configured to store at least one instruction, and store homomorphic ciphertexts storing a plurality of variable data in an encrypted state in plurality, and a processor configured to execute at least one instruction, and the processor is configured to generate, by executing the at least one instruction, number data corresponding to a variable combination by using a bin mask having different variable data classified for each of the homomorphic ciphertexts based on an operation instruction on the plurality of homomorphic ciphertexts being received.

Abstract: Disclosed is a calculation apparatus. The calculation apparatus comprises a memory which stores at least one instruction and a processor which executes the at least one instruction, wherein the processor executes the at least one instruction to store a predetermined base prime number, invert the bits of information about the pre-stored base prime number to generate first prime number information different from the base prime number information, and perform modular calculation on a plurality of ciphertexts by using the generated first prime number information.

Abstract: A method of generating a secret key according to one embodiment includes generating a share of each of a user and a plurality of other users for a secret key of the user, providing the share of each of the plurality of other users to a user terminal of each of the plurality of other users, receiving a share of the user for a secret key of each of the plurality of other users from the user terminal of each of the plurality of other users, and generating a new secret key of the user using the share of the user for the secret key of the user and the shares of the user for the secret key of each of the plurality of other users.

Abstract: Disclosed are a calculation device for encryption using a public key and an encryption method thereof. The present method comprises: a step for setting a secret key, and generating a public key using the secret key and an error extracted from a discrete Gaussian distribution or a distribution that is within a short statistical distance thereto; and a step for applying the public key to a message, and then performing a rounding process to encrypt the message. Accordingly, encryption efficiency can be enhanced.

Abstract: Disclosed is a method of generating digital signature information comprising: receiving a message; computing a particular solution in which a result of calculating the particular solution in a public key becomes a function-processed output value predetermined in the received message; and generating digital signature information for the message using the computed particular solution, wherein the public key is computed using a ring having a dimension (d) represented by a power of 2 and an integer multiplication of 3 or more.

Abstract: Disclosed is a ciphertext computation method. The ciphertext computation method includes: receiving a modular computation command for a plurality of ciphertexts; performing a modular computation for the plurality of ciphertexts by using a lookup table storing a plurality of predetermined prime number information; and outputting a result of the computation.

Abstract: A method of operating a homomorphic ciphertext is disclosed. The method of operating a homomorphic ciphertext includes receiving a non-polynomial operation command with respect to a homomorphic ciphertext, computing an approximate polynomial function corresponding to the non-polynomial operation, performing an operation of the homomorphic ciphertext using the computed polynomial function, and outputting the operated homomorphic ciphertext, wherein the approximate polynomial function is a second approximate polynomial function which is obtained by extending a first approximate polynomial function to have a second range wider than the first range having a preset accuracy with the non-polynomial operation within a first range.

Abstract: Disclosed is a calculation device. The present calculation device includes: a memory for storing a plurality of homomorphic ciphertexts for an approximate message including an error; and a processor for sorting the plurality of homomorphic ciphertexts by using a 5-way sorter which can sort five homomorphic ciphertexts in a single stage.

Abstract: An encryption method includes: calculating a second random matrix using a first random matrix and a secret key, and generating a ciphertext corresponding to a message using the second random matrix. The generating of the ciphertext includes: performing a rounding process for sending the generated ciphertext to a smaller modulus area. The generating of the ciphertext includes performing message encryption without Gaussian sampling.

Abstract: A data sharing method of a user device is provided. The data sharing method includes receiving, from a server device storing information, a private key corresponding to the information, performing a homomorphic encryption of the private key by a homomorphic encryption key provided from the server device, and generating a switch key, and uploading the switch key to a blockchain system. Accordingly, a more effective and clear data sharing is provided.

Abstract: Disclosed is a method of arithmetic operation. The arithmetic operation includes receiving an input value, generating an output value by reflecting the input value to a preset arithmetic circuit on a finite commutative ring and a first polynomial function to verify the output value, and transferring the generated output value and the first polynomial function to an external device.

Abstract: A mobile device is disclosed. The device includes a communicator, a GPS unit for calculating location information, a memory, a display, and a processor, and the processor is configured to generate movement path information of the mobile device by performing homomorphic encryption of a plurality of pieces of location information stored in the memory, transmit the movement path information to a server apparatus through the communicator, based on operation result data obtained by operating based on the movement path information and comparison target path information being transmitted from the server apparatus, decrypt the operation result data, and output a message notifying whether a route overlaps the comparison target path information based on a decrypted result through the display. Therefore, the route overlap is rapidly and accurately confirmed without invasion of privacy.

Abstract: A method for processing an encryption is provided. The method for processing an encryption includes the steps of linearly transforming a homomorphic encryption for an approximate message including an error, performing an approximate modulus operation for the linearly transformed homomorphic encryption by using a multi-degree polynomial set such that input values within a predetermined range are approximate to an integer point, and linearly transforming the homomorphic encryption which was approximately modulus operated into a form of encryption.

Abstract: Disclosed is a ciphertext calculation method. The ciphertext calculation method comprises the steps of: receiving a comparative calculation command for a plurality of ciphertexts of the same type; performing a calculation by reflecting the plurality of ciphertexts of the same type on a synthesis function corresponding to the comparative calculation command; and outputting the calculated ciphertexts of the same type.

Abstract: An encoding method is disclosed. The present encoding method comprises the steps of: receiving a plurality of messages; encoding the plurality of messages into a polynomial expression having been multivariately defined, and encoding the multivariately defined polynomial expression so as to generate a homomorphic cyphertext.

Abstract: A calculation device is disclosed. The calculation device includes: a memory storing at least one instruction and identity information; and a processor performing the at least one instruction, wherein the processor may randomly sample small elements, generate a function-processed output value by function-processing the stored identity information, and generate an encrypted text for a message by using a master public key computed using a ring having a dimension (d) represented by a power of 2 and an integer multiplication of 3 or more, the sampled small elements and the function-processed output value.

Abstract: An encryption method is disclosed. The encryption method includes calculating a secret key from a ring as a set closed for addition and multiplication defined between elements, generating a plurality of partial secret keys using the calculated secret key and a random matrix, and distributing the plurality of generated partial secret keys.

Abstract: An operation apparatus and method for processing a homomorphic encrypted message are disclosed. The method includes producing an approximate polynomial corresponding to an operation function to be applied to a homomorphic encrypted message and approximately operating the homomorphic encrypted message using the approximate polynomial. Thus, an encrypted message may be efficiently processed.