Abstract: Systems and methods for enabling constant plaintext space in bootstrapping in fully homomorphic encryption (FHE) are disclosed. A computer-implemented method for producing an encrypted representation of data includes accessing a set of encoded digits. The method includes applying an inverse linear transformation to the set of encoded digits to obtain a first encoded polynomial. The method includes applying a modulus switching and dot product with bootstrapping key to add an error term to each of the encoded digits in the first polynomial to obtain a second encoded polynomial. The method includes applying a linear transformation to the second encoded polynomial to obtain a first batch encryption. The method includes applying digit extraction to the first batch encryption to obtain a second batch encryption, the second batch encryption corresponding to the set of encoded digits without the error term.

Abstract: A decryption method includes: receiving a homomorphic ciphertext; and obtaining a result value added an error value at a message from the received homomorphic ciphertext. The error is disposed on the least significant bit (LSB) side in the homogeneous ciphertext, and the message is disposed at a position adjacent to the error.

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.

Abstract: An encryption method of a terminal device includes: setting a scaling factor; and reflecting the scaling factor in a message to be encrypted, and performing encryption using a public key to generate a homomorphic ciphertext. The homomorphic encryption is, based on a decryption being performed, in a form that a result value obtained by adding an error value to a value obtained by reflecting the scaling factor in the message is restored.

Abstract: Systems and methods for enabling constant plaintext space in bootstrapping in fully homomorphic encryption (FHE) are disclosed. A computer-implemented method for producing an encrypted representation of data includes accessing a set of encoded digits. The method includes applying an inverse linear transformation to the set of encoded digits to obtain a first encoded polynomial. The method includes applying a modulus switching and dot product with bootstrapping key to add an error term to each of the encoded digits in the first polynomial to obtain a second encoded polynomial. The method includes applying a linear transformation to the second encoded polynomial to obtain a first batch encryption. The method includes applying digit extraction to the first batch encryption to obtain a second batch encryption, the second batch encryption corresponding to the set of encoded digits without the error term.

Abstract: An encryption method is provided. According to the encryption method, a scaling factor may be reflected in a message and then, a homomorphic ciphertext may be generated using a public key. The generated ciphertext is, when decryption is performed, generated in a form that a result value obtained by adding an error value to a value obtained by reflecting the scaling factor in the message is restored. Accordingly, a homomorphic ciphertext capable of being computed in a ciphertext state can be effectively generated.

Abstract: A decryption method includes: receiving a homomorphic ciphertext; and obtaining a result value added an error value at a message from the received homomorphic ciphertext. The error is disposed on the least significant bit (LSB) side in the homogeneous ciphertext, and the message is disposed at a position adjacent to the error.

Abstract: An encryption method of a terminal device includes: setting a scaling factor; and reflecting the scaling factor in a message to be encrypted, and performing encryption using a public key to generate a homomorphic ciphertext. The homomorphic encryption is, based on a decryption being performed, in a form that a result value obtained by adding an error value to a value obtained by reflecting the scaling factor in the message is restored.

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.

Abstract: An encryption method is provided. According to the encryption method, a scaling factor may be reflected in a message and then, a homomorphic ciphertext may be generated using a public key. The generated ciphertext is, when decryption is performed, generated in a form that a result value obtained by adding an error value to a value obtained by reflecting the scaling factor in the message is restored. Accordingly, a homomorphic ciphertext capable of being computed in a ciphertext state can be effectively generated.

Abstract: Systems and methods for enabling constant plaintext space in bootstrapping in fully homomorphic encryption (FHE) are disclosed. A computer-implemented method for producing an encrypted representation of data includes accessing a set of encoded digits. The method includes applying an inverse linear transformation to the set of encoded digits to obtain a first encoded polynomial. The method includes applying a modulus switching and dot product with bootstrapping key to add an error term to each of the encoded digits in the first polynomial to obtain a second encoded polynomial. The method includes applying a linear transformation to the second encoded polynomial to obtain a first batch encryption. The method includes applying digit extraction to the first batch encryption to obtain a second batch encryption, the second batch encryption corresponding to the set of encoded digits without the error term.