Improving the Efficiency of Homomorphic Encryption Schemes

• Main Author: Hu, Yin
• Other Authors: Lifeng Lai, Committee Member
• Format: Others
• Published: Digital WPI 2013
• Subjects: homomorphic encryption
• Online Access: https://digitalcommons.wpi.edu/etd-dissertations/171; https://digitalcommons.wpi.edu/cgi/viewcontent.cgi?article=1170&context=etd-dissertations

In this dissertation, we explore different approaches to practical homomorphic encryption schemes. For partial homomorphic encryption schemes, we observe that the versatility is the main bottleneck. To solve this problem, we propose general approaches to improve versatility of them by either extending the range of supported circuits or extending the message space. These general approaches can be applied to a wide range of partial HE schemes and greatly increase the number of applications that they support. For fully homomorphic encryption schemes, the slow running speed and the large ciphertext are the main challenges. Therefore, we propose efficient implementations as well as methods to compress the ciphertext. In detail, the Gentry Halevi FHE scheme and the LTV FHE scheme are implemented and the resulting performance shows significant improvement over previous works. For ciphertext compression, the concept of scheme conversion is proposed. Given a scheme converter, we can convert between schemes with compact ciphertext for communication and homomorphic schemes for computation.