  We propose a federated Function-as-a-Service (FaaS) execution model that
provides secure and stateful execution in both Cloud and Edge environments. The
FaaS workers, called Paranoid Stateful Lambdas (PSLs), collaborate with one
another to perform large parallel computations. We exploit cryptographically
hardened and mobile bundles of data, called DataCapsules, to provide persistent
state for our PSLs, whose execution is protected using hardware-secured TEEs.
To make PSLs easy to program and performant, we build the familiar Key-Value
Store interface on top of DataCapsules in a way that allows amortization of
cryptographic operations. We demonstrate PSLs functioning in an edge
environment running on a group of Intel NUCs with SGXv2.
  As described, our Secure Concurrency Layer (SCL), provides
eventually-consistent semantics over written values using untrusted and
unordered multicast. All SCL communication is encrypted, unforgeable, and
private. For durability, updates are recorded in replicated DataCapsules, which
are append-only cryptographically-hardened blockchain with confidentiality,
integrity, and provenance guarantees. Values for inactive keys are stored in a
log-structured merge-tree (LSM) in the same DataCapsule. SCL features a variety
of communication optimizations, such as an efficient message passing framework
that reduces the latency up to 44x from the Intel SGX SDK, and an actor-based
cryptographic processing architecture that batches cryptographic operations and
increases throughput by 81x.
