An Attack on a Fully Homomorphic Encryption Scheme
Fully-Homomorphic-Encryption (FHE) is a novel technique applied to cloud-computation. It is for such procedure. The user needs to obtain the output of ring-operations in plaintext space, but wants to compute nothing but only decryption. The sever implements "Homomorphic operations in ciphertext space" of these operations in plaintext space. In this paper, the authors present an attack on a fully homomorphic encryption scheme on PKC2010. They construct a modified secret key, a modified decryption algorithm and a subset of the ciphertext space. When the ciphertext is from the subset, they can correctly decrypt it by their modified secret key and modified decryption algorithm. They also discuss when their modified decryption algorithm is efficient, and when the subset is not negligible.