MarriageTheoremのこと

_ 謹賀新年。年内分の日記が書き終わらなかったので急いで書き終えるなど。

_ IACR ePrint 2014/1021まで確認済み、ECCC 2003年分まで確認済み

_ 気になった論文：Controlled Homomorphic Encryption: Definition and Construction, Yvo Desmedt and Vincenzo Iovino and Giuseppe Persiano and Ivan Visconti, http://eprint.iacr.org/2014/989

Fully Homomorphic Encryption schemes (FHEs) and Functional Encryption schemes (FunctEs) have a tremendous impact in Cryptography both for the natural questions that they address and for the wide range of applications in which they have been (sometimes critically) used. In this work we put forth the notion of a Controllable Homomorphic Encryption scheme (CHES), a new primitive that includes features of both FHEs and FunctEs. In a CHES it is possible (similarly to a FHE) to homomorphically evaluate a ciphertext Ct = Enc(m) and a circuit C therefore obtaining Enc(C(m)) but only if (similarly to a FunctE) a token for C has been received from the owner of the secret key. We discuss difficulties in constructing a CHES and then show a construction based on any FunctE.