Similarity Calculation System with Homomorphic Encryption

ChangeBridge: Patent Grants - Networking (H04L)

Published April 7th, 2026

Detected April 7th, 2026

Summary

USPTO granted patent US12598057B2 to NEC Corporation on April 7, 2026, covering a similarity calculation system using homomorphic encryption. The system enables secure distance calculations between vectors where one vector remains encrypted on a similarity calculation apparatus while the other is input from a terminal. The invention uses weighted distance tables and additive homomorphic encryption to compute ciphertext sums of element distances.

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What changed

USPTO issued patent US12598057B2 to NEC Corporation, covering a similarity calculation system that performs secure distance calculations between vectors using homomorphic encryption. The system transmits ciphertexts of vector elements and weighted distance tables from the similarity calculation apparatus to an input terminal, which then computes ciphertexts of element distances and sums using additive homomorphic encryption before returning results. The patent contains 12 claims and is classified under H04L 9/008 and G09C 1/06.

For technology companies and software developers, this patent represents potential licensing opportunities or constraints for developing encrypted similarity or distance calculation systems. Competitors in secure computing, privacy-preserving machine learning, or encrypted database search may need to design around this NEC patent or seek licensing arrangements to avoid infringement.

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Source document (simplified)

← USPTO Patent Grants

Similarity calculation system, similarity calculation apparatus, similarity calculation method, and similarity calculation program

Grant US12598057B2 Kind: B2 Apr 07, 2026

Assignee

NEC CORPORATION

Inventors

Sanami Nakagawa, Toshiyuki Isshiki, Hiroto Tamiya

Abstract

A similarity calculation system calculating a distance between a first vector stored in a similarity calculation apparatus and a second vector entered from an input terminal wherein the similarity calculation apparatus transmits to the input terminal a ciphertext of each element of the first vector and a weighted distance table with respect to combinations of possible values of the elements of the first vector and the second vector, and the input terminal refers to the weighted distance table to calculate a ciphertext of element distances for all combinations of the value of a single element of the second vector and possible values of elements of the first vector, calculates the ciphertexts of the sum of the element distances for each element of the second vector using additive homomorphic encryption, and transmits the ciphertext of the sum to the similarity calculation apparatus.