CRYPTO LAB INC.

Disclosed is an operation device. The operation device includes a memory storing at least one instruction; and a processor configured to execute the at least one instruction, and the processor, by executing the at least one instruction, may perform encoding or decoding for an approximate homomorphic ciphertext using a predetermined matrix having only a half of an element of a matrix corresponding to a canonical embedding function.

An electronic device and a controlling method thereof are disclosed. Specifically, the electronic device performs bootstrapping for an input ciphertext encrypted with integer data, obtains an intermediate ciphertext by transforming the integer data to complex root of unity data, obtains, based on the intermediate ciphertext, a polynomial for approximating a pre-defined function in a complex root of unity, and obtains, by inputting the complex root of unity data in the polynomial to approximately perform an operation corresponding to the function in a ciphertext state, an output ciphertext comprising a function value corresponding to the integer data.

Provided are a method and an electronic device for performing convolutional neural network operations on a batch of input images using homomorphic encryption. The method includes: for each channel of the batch of the input images, grouping pixel values at the same location in the images included in the batch into a single vector, and encrypting the grouped vectors using a homomorphic encryption method to obtain a first ciphertext; for each channel and each coefficient of the ciphertext, grouping coefficients of the first ciphertext corresponding to all pixel locations to generate polynomials, and configuring the polynomials into a single matrix; multiplying the matrix by a polynomial matrix representing a convolution filter to obtain a result matrix, and performing a modulo operation on each element of the result matrix to generate an encrypted convolution operation result, the operation being performed on unencrypted matrices; and rearranging polynomial coefficients of the result matrix to generate a second ciphertext for the batch of the images after the convolution layer is applied, in which the second ciphertext is encrypted by the same homomorphic encryption method as the first ciphertext.

Disclosed is an electronic apparatus. The electronic apparatus includes: a memory storing a plurality of homomorphic encryptions and lookup table information; a communication apparatus configured to perform communication with an external apparatus; and a processor configured to retrieve the homomorphic encryption in response to a requested query, wherein the lookup table information stores data acquired by homomorphically encrypting keyword information and index information that respectively correspond to the plurality of homomorphic encryptions, and the processor is configured to retrieve the homomorphically encrypted index information by using received query information and the lookup table information in case of receiving the query information from the external apparatus, and control the communication apparatus to transmit the retrieved index homomorphic encryption to the electronic apparatus.

An electronic apparatus for generating a homomorphic encrypted message includes: a processor configured to generate a mask homomorphic encrypted message by homomorphically comparing the homomorphic encrypted message with the index data in case that a calculation command of the predetermined function for the homomorphic encrypted message is input, generate an intermediate homomorphic encrypted message by homomorphically multiplying the generated mask homomorphic encrypted message by the function result data, generate a function-result encrypted message for the homomorphic encrypted message by computing sum of values in a plurality of slots of the intermediate homomorphic encrypted message.

Disclosed is an electronic apparatus. The apparatus includes: a memory storing instructions; a communication interface; and at least one processor including processing circuitry, wherein the at least one processor is configured to obtain a ciphertext by using a learning-with-error (LWE)-based encryption scheme or an exact Cheon-Kim-Kim-Song (CKKS)-based encryption scheme, and control the communication interface to transmit, to a server, a seed for generating a random vector included in the ciphertext and upper bits of an integer included in the ciphertext.

Disclosed is a server device. The server device includes a communication unit configured to perform communication with an electronic device; a memory configured to store an artificial intelligence (AI) model for performing computation in an encrypted state; and a processor, in which the processor is configured tobased on receiving homomorphic ciphertext of CinS-encoded data obtained by performing CinS encoding on a plurality of images from the electronic device through the communication unit, transmit the encryption computation result to the electronic device through the communication unit by obtaining an encryption computation result by inputting the homomorphic ciphertext to the AI model, wherein. the AI model performs each of convolutional computation based on the CinS-encoded data and activation function computation based on slot-encoded data converted from the CinS-encoded data a plurality of times.

An operation apparatus performing matrix multiplication of a homomorphic encryption is disclosed. The operation apparatus includes a memory configured to store at least one instruction and a plurality of homomorphic ciphertexts, and a processor configured to execute the at least one instruction. The processor is configured to generate first matrix data having a row of a predetermined size and a column of a predetermined size using the plurality of homomorphic ciphertexts, generate a plurality of third matrix data having a row which is the size of the predetermined column and the column of the predetermined size by arranging second matrix data having a row which is 1/n size of the predetermined column and the column of the predetermined size sequentially n-times, and perform a homomorphic multiplication operation between same rows and same columns using the first matrix data and the generated respective third matrix data.

A server device is provided. The server device includes an interface configured to communicate with an application device in which an application that uses plaintext data is installed, a memory, and a processor, wherein the processor is configured to generate a homomorphic encrypted master key corresponding to the application device and index information for the master key, store the homomorphic encrypted master key and the index information in the memory, and provide the index information to the application device through the interface. Accordingly, various data processing may be performed, while security is maintained without dedicated hardware.

Provided is a control method of a system including a plurality of electronic apparatuses, a transcryptor, and a server. The method includes: obtaining, by the apparatuses included in the system, a first public key for the apparatuses included in the system by using a threshold public key encryption scheme, and obtaining, by each of the plurality of electronic apparatuses, a secret key share corresponding to each apparatus; generating, by the transcryptor, a second public key and a private key based on a non-threshold fully homomorphic encryption scheme, and providing the second public key to the server and the plurality of electronic apparatuses; generating a ciphertext, by each of the plurality of electronic apparatuses, by encrypting plaintext data using the second public key, and then transmitting the generated ciphertext to the server; obtaining, by the server, a homomorphic computation ciphertext by performing homomorphic computation on the received ciphertext using a circuit for combining threshold public key encryption; transmitting, by the server, the homomorphic computation ciphertext to the transcryptor; decrypting, by the transcryptor, the homomorphic computation ciphertext using the private key, and broadcasting the decrypted homomorphic computation ciphertext to the plurality of electronic apparatuses; and obtaining a final decryption result, by a qualified group of electronic apparatuses among the plurality of electronic apparatuses, by performing partial decryption on the homomorphic computation ciphertext using the secret key shares and by combining the partial decryption results.