MarriageTheoremのこと

_ IACR ePrint 2015/516まで確認済み、ECCC 2003年分まで確認済み

_ 気になった論文1：Practical Fully Homomorphic Encryption without Noise Reduction, Dongxi Liu, http://eprint.iacr.org/2015/468

We present a new fully homomorphic encryption (FHE) scheme that is efficient for practical applications. The main feature of our scheme is that noise reduction considered essential in current FHE schemes, such as boot strapping and modulus switching, is not needed in our scheme, because it allows arbitrarily large noises in its ciphertexts. A ciphertext in our scheme is a vector with its dimension specified as a security parameter of the encryption key. The dimension of ciphertexts does not change with homomorphic operations and all ciphertext elements are in a finite domain, so our scheme is compact. In addition, our scheme can directly encrypt big integers, rather than only bit messages.

We proved the hardness of recovering encryption keys from any number of ciphertexts with chosen plaintexts and then the semantic security of our scheme. The hardness of recovering keys from ciphertexts is based on the approximate greatest common divisors problem. We implemented a prototype of our scheme and evaluated its concrete performance extensively from the aspects of encryption, decryption, homomorphic operations, and bitwise operators over ciphertexts. The efficiency of our scheme is confirmed by the evaluation result.

_ 気になった論文2：Fully Homomorphic Encryption without bootstrapping, Masahiro Yagisawa, http://eprint.iacr.org/2015/474

Gentry’s bootstrapping technique is the most famous method of obtaining fully homomorphic encryption. In this paper I propose a new fully homomorphic encryption scheme on non-associative octonion ring over finite field without bootstrapping technique. The security of the proposed fully homomorphic encryption scheme is based on computational difficulty to solve the multivariate algebraic equations of high degree while the almost all multivariate cryptosystems proposed until now are based on the quadratic equations avoiding the explosion of the coefficients. Because proposed fully homomorphic encryption scheme is based on multivariate algebraic equations with high degree or too many variables, it is against the Gröbner basis attack, the differential attack, rank attack and so on. The key size of this system and complexity for enciphering/deciphering become to be small enough to handle.