Announcing HPU on FPGA: The First Open-source Hardware Accelerator for FHE

Zama has introduced the first open-source hardware accelerator for Fully Homomorphic Encryption (FHE), named the Homomorphic Processing Unit (HPU), which operates on a Field-Programmable Gate Array (FPGA). Released alongside TFHE-rs v1.2, the HPU is a processor that computes directly on encrypted data, equipped with a register file, control logic, and an arithmetic unit capable of executing instructions over encrypted operands. Unlike traditional accelerators that enhance cryptographic primitives, the HPU performs boolean and integer operations directly on encrypted data, with its instruction set being fully customizable for developers. The integration of the HPU into the TFHE-rs library allows users to execute encrypted operations using the same high-level API previously used for CPUs or GPUs, enhancing performance and energy efficiency. Currently running at 350 MHz on a 7nm FPGA with the capability to process around 13,000 Programmable Bootstrapping operations per second, the HPU is noted for its speed and lower cost per unit compared to CPUs and GPUs. Although not fully production-ready, Zama is working to integrate it into their product line by 2025, alongside developing multi-HPU servers to improve FHE operation efficiency. The open-source nature of the HPU stack, which includes systemVerilog hardware design and TFHE-rs integration, invites developers and researchers to audit, extend, and repurpose the technology for their projects.