As cloud computing, internet of things (IoT) and blockchain ??technology become increasingly
prevalent, there is an urgent ?need ??to protect the privacy of massive volumes of sensitive ??data
collected or stored in distributed computer networks or ??cloud servers, as many of the
networks or servers can be ??vulnerable to external and internal threats such as ??malicious
hackers or curious insiders. The Holy-Grail of ??cryptography is to have practical fully
homomorphic encryption ??(FHE) schemes that allow any third party (including cloud ??servers,
hackers, miners or insiders) to perform searching or ??analytics of an arbitrary function on
encrypted data without ??decryption, while no information on the original data is ever leaked. ??The
breakthrough was made by Gentry in 2009 who discovered the ??first FHE scheme, and since
then many improvements have been ?made ??on more efficient homomorphic encryption
schemes. The main ??bottlenecks are in bootstrapping speed and large cipher expansion ??factor
(the size ratio of ciphertexts over plaintexts): the ??current best FHE schemes can compute
bootstrapping of one bit ??operation in a fraction of a second and have a cipher expansion ??factor
of 8,000. In this talk, we present compact FHE schemes ??that achieve cipher expansion factor
of 2.5 to 6 under secret ?key ??and 6.5 to 20 under public key while the bootstrapping ??speed
matches the current best FHE schemes.