CPC H04L 9/085 (2013.01) [H04L 9/008 (2013.01); H04L 9/0819 (2013.01); H04L 9/0891 (2013.01)] | 16 Claims |
1. 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 common public key;
providing the ciphertext for the secret key of the user to each of user terminals of a plurality of other users;
receiving a ciphertext for a secret key of each of the plurality of other users, which is encrypted using the common public key, from each of the user terminals of the plurality of other users;
generating an evaluation key share of the user from the ciphertext for the secret key of the user and the ciphertext for the secret key of each of the plurality of other users using a homomorphic addition operation on the basis of the secret key of the user;
receiving, from each of the plurality of other users, an evaluation key share of each of the plurality of other users, which is generated from the ciphertext for the secret key of the user and the ciphertext for the secret key of each of the plurality of other users, using a homomorphic addition operation on the basis of the secret key of each of the plurality of other users; and
generating an evaluation key for a homomorphic multiplication operation for a homomorphic multiplication operation for the ciphertext, which is encrypted using the 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.
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