International Association
for Cryptologic Research

In this paper we present an attack on a fully homomorphic encryption scheme on PKC2010.

We construct a modi¯ed secret key, a modi¯ed decryption algorithm and a subset of the ciphertext

space. When the ciphertext is from the subset, we can correctly decrypt it by our modi¯ed secret key

and modi¯ed decryption algorithm. We also discuss when our modi¯ed decryption algorithm is e±cient,

and when the subset is not negligible.