  Fully Homomorphic Encryption (FHE) allows for secure computation on encrypted
data. Unfortunately, huge memory size, computational cost and bandwidth
requirements limit its practicality. We present BASALISC, an architecture
family of hardware accelerators that aims to substantially accelerate FHE
computations in the cloud. BASALISC is the first to implement the BGV scheme
with fully-packed bootstrapping -- the noise removal capability necessary for
arbitrary-depth computation. It supports a customized version of bootstrapping
that can be instantiated with hardware multipliers optimized for area and
power.
  BASALISC is a three-abstraction-layer RISC architecture, designed for a 1 GHz
ASIC implementation and underway toward 150mm2 die tape-out in a 12nm GF
process. BASALISC's four-layer memory hierarchy includes a two-dimensional
conflict-free inner memory layer that enables 32 Tb/s radix-256 NTT
computations without pipeline stalls. Its conflict-resolution permutation
hardware is generalized and re-used to compute BGV automorphisms without
throughput penalty. BASALISC also has a custom multiply-accumulate unit to
accelerate BGV key switching.
  The BASALISC toolchain comprises a custom compiler and a joint performance
and correctness simulator. To evaluate BASALISC, we study its physical
realizability, emulate and formally verify its core functional units, and we
study its performance on a set of benchmarks. Simulation results show a speedup
of more than 5,000 times over HElib -- a popular software FHE library.
