Client-optimized algorithms and acceleration for encrypted compute offloading

Homomorphic Encryption (HE) enables secure cloud offload processing on encrypted data. HE schemes are limited in the complexity and type of operations they can perform, motivating client-aided implementations that distribute computation between client (unencrypted) and server (encrypted). Prior client-aided systems optimize server performance, ignoring client costs: client-aided models put encryption and decryption on the critical path and require communicating large ciphertexts. We introduce Client-aided HE for Opaque Compute Offloading (CHOCO), a client-optimized system for encrypted offload processing. CHOCO reduces ciphertext size, reducing communication and computing costs through HE parameter minimization and through “rotational redundancy”, a new HE algorithm optimization. We present Client-aided HE for Opaque Compute Offloading Through Accelerated Cryptographic Operations (CHOCO-TACO), an accelerator for HE encryption and decryption, making client-aided HE feasible for even resource-constrained clients. CHOCO supports two popular HE schemes (BFV and CKKS) and several applications, including DNNs, PageRank, KNN, and K-Means. CHOCO reduces communication by up to 2948× over prior work. With CHOCO-TACO client enc-/decryption is up to 1094× faster and uses up to 648× less energy.