Applying Metamorphic Testing to Homomorphic Cryptography

Homomorphic encryption schemes allow applications to perform operations on encrypted data without decrypting the data. This is possible due to homomorphisms between the plaintext space and the ciphertext space. The open source PALISADE software library implements a collection of homomorphic encryption schemes. The work described in this paper explores how metamorphic testing, a testing methodology alleviating the oracle problem, can be used to test the PALISADE library. Some faults are discovered and the applicability of metamorphic testing to homomorphic encryption is confirmed.