Patent ID: 11930104
Assignee: SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION
Field: Digital communication (Electrical engineering)
Classification: CPC H | IPC H

Claim 10:
11. A method of generating an evaluation key, the method performed by a computing device comprising one or more processors and a memory in which one or more programs to be executed by the one or more processors are stored, the method comprising:
generating a ciphertext for a secret key of a user using a public key of the user;
providing the ciphertext for the secret key of the user to a user terminal of each of a plurality of other users;
receiving, from the user terminal of each of the plurality of other users, a ciphertext for a secret key of each of the plurality of other users, which is encrypted using a public key of each of the plurality of other users;
generating an intermediate evaluation key using the ciphertext for the secret key of the user and the ciphertext for the secret key of each of the plurality of other users;
generating an evaluation key share of the user using the secret key of the user and the intermediate evaluation key;
receiving, from each of the plurality of other users, an evaluation key share of each of the plurality of other users, which is generated using the secret key of each of the plurality of other users and the intermediate evaluation key; and
generating an evaluation key for a homomorphic multiplication operation for a ciphertext, which is encrypted using a common public key, by using the evaluation key share of the user and the evaluation key share of each of the plurality of other users.