Patent ID: 9473302
Filing Date: 2016-10-18
CPC Classification: H04L

Claim Text:
1. A ciphertext processing device comprising: a memory, and a processor coupled to the memory wherein the processor executes a process comprising: first acquiring a first polynomial in which a plurality of bits included in a numerically vectorized first text data are set to coefficients in an ascending order and which is encrypted in a homomorphic encryption with a first public key and a first square-value polynomial in which a plurality of bits included in square-value vector data of each component of the numerically vectorized first text data are set to coefficients in the ascending order and which is encrypted in the homomorphic encryption with the first public key; second acquiring a second polynomial in which a plurality of bits included in a numerically vectorized second text data are set to coefficients in a descending order and which is encrypted in the homomorphic encryption with the first public key and a second square-value polynomial in which a plurality of bits included in square-value vector data of each component of the numerically vectorized second text data are set to coefficients in the descending order and which is encrypted in the homomorphic encryption with the first public key; and calculating a first auxiliary data item for aggregating the each coefficient of the each term of the first polynomial, calculating a second auxiliary data item for aggregating the each coefficient of the each term of the first square-value polynomial, and calculating an encryption norm distance between the numerically vectorized first text data and the numerically vectorized second text data by executing a pattern matching which determines whether the numerically vectorized second text data is included in the numerically vectorized first text data, while maintaining the encrypting, using the first polynomial, the first square-value polynomial, the second polynomial, the second square-value polynomial, the first auxiliary data item, and the second auxiliary data item.