International Business Machines Corporation

Wei Zhang

David Francis Bacon

Graham Anthony Bent

Flavio Alvarenga Bergamaschi

In computer-implemented technology for comparing first and second values that are encrypted according to a fully homomorphic encryption scheme, the following function is computed: where &#x3b5;(.) is a fully homomorphic encryption scheme.

Performing efficient comparison operations on encrypted data

A querying node generates public keys, secret keys, and switch key matrices. A public key associated with a first level and the switch key matrices are sent to a receiving node. The receiving node generates a key-value table, mapping values to keys, and encodes the keys and values using a polynomial ring of a predetermined type. The querying node encodes using a polynomial ring of the same predetermined type, then encrypts a query, using a public key, and sends the query to the receiving node. The receiving node performs a homomorphic comparison of the encrypted, encoded query with each encoded key entry in the encoded key-value store to determine a comparison result. The receiving node sums the results for each of the value entries and returns the summed result to the querying node. The querying node decrypts and decodes the received result using the corresponding secret key.

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Egham, United Kingdom

Wei Zhang