Abstract: Disclosed is a server. The server includes a camera, a memory configured to store an encrypted database generated based on a plurality of feature vectors corresponding to a plurality of users, and a processor configured to acquire an image obtained by capturing a target user's face using the camera and transform a feature vector acquired from the image based on transformation and identify the target user based on the transformed feature vector and the encrypted database. The encrypted database is generated by transforming the plurality of feature vectors based on the transformation and homomorphically encrypting the plurality of transformed feature vectors. The transformation transforms components of the feature vectors into 1, ?1, or 0 depending on magnitudes and signs of the components of the feature vectors.

Abstract: Disclosed is a server. The server includes a camera, a memory configured to store an encrypted database generated based on a plurality of feature vectors corresponding to a plurality of users, and a processor configured to acquire an image obtained by capturing a target user's face using the camera and transform a feature vector acquired from the image based on transformation and identify the target user based on the transformed feature vector and the encrypted database. The encrypted database is generated by transforming the plurality of feature vectors based on the transformation and homomorphically encrypting the plurality of transformed feature vectors. The transformation transforms components of the feature vectors into 1, ?1, or 0 depending on magnitudes and signs of the components of the feature vectors.