Aloha-HE: A Low-Area Hardware Accelerator for Client-Side Operations in Homomorphic Encryption

Homomorphic encryption (HE) has gained broad attention in recent years as it allows computations on encrypted data enabling secure cloud computing. Deploying HE presents a notable challenge since it introduces a performance overhead by orders of magnitude. Hence, most works target accelerating server-side operations on hardware platforms, while little attention has been given to client-side operations. In this paper, we present a novel design methodology to implement and accelerate the client-side HE operations on area-constrained hardware. We show how to design an optimized floating-point unit tailored for the encoding of complex values. In addition, we introduce a novel hardware-friendly algorithm for modulo-reduction of floating-point numbers and propose various concepts for achieving efficient resource sharing between modular ring and floating-point arithmetic. Finally, we use this methodology to implement an end-to-end hardware accelerator, Aloha-HE, for the client-side operations of the CKKS scheme. In contrast to existing work, Aloha-HE supports both encoding and encryption and their counterparts within a unified architecture. Aloha-HE achieves a speedup of up to 59x compared to prior hardware solutions.