SCARV: a side-channel hardened RISC-V platform

Acting as a component part of the wider SCARV project, the RISC-V compatible SCARV micro-controller (comprising a processor core and SoC) is the eponymous, capstone output, e.g., representing a demonstrator for the XCrypto ISE.

Overview

In various ways, RISC-V is acting as a catalyst for research in computer architecture, while also remaining a practical, industrially relevant option for concrete products. A central theme is that the open ISA specifically has naturally led to a large number of associated, open-source implementations. This, in turn, allows direct use or refinement of such implementations in order to fit or react to specific requirements of a given use-case, market, or domain; documented implementations reflect this fact via their diversity, and maturity.

One such domain is that of security, where openness has the auxiliary benefit of transparency: because many implementations of RISC-V are available under open-source licenses, they allow forms of security evaluation or verification that would be impossible with proprietary alternatives. This is a massive advantage where trust is important, as evidenced by the use of RISC-V as a basis for projects such as OpenTitan.

The SCARV project has a specific remit, specifically focusing on the support of cryptography as an enabling technology within more general solutions for challenges related to (cyber-)security. Representing the capstone output of said project, the SCARV micro-controller aims to support efficient (e.g., low-latency, and low-footprint), secure (e.g., wrt. implementation attacks) execution of software-based cryptographic workloads. Of course, it is one instance within a large design space: this means it will not be a suitable choice for every use-case. Even then, however, it acts as an effective reference and demonstrator platform, for other components of the overarching project (e.g., the XCrypto ISE).

Organisation

├── bin                     - scripts (e.g., environment configuration)
├── build                   - working directory for build
├── doc                     - documentation
│   └── tex                   - LaTeX content
└── extern                  - external resources (e.g., submodules)
    ├── scarv-cpu             - submodule: scarv/scarv-cpu
    ├── scarv-soc             - submodule: scarv/scarv-soc
    ├── texmf                 - submodule: scarv/texmf
    └── wiki                  - submodule: scarv/scarv.wiki

Originally this was a monorepo that housed all resources in one place, but, to make them easier to manage, it now acts as a container where each resource is housed in dedicated submodule. Specifically, these include:

• scarv/scarv-cpu houses the processor core implementation; it includes a 5-stage, single issue, in-order pipeline, and implements the RISC-V 32-bit integer base architecture (i.e., RV32I) plus

  • the standard Compressed (C) and Multiply (M) extensions, and
  • the non-standard XCrypto extension.

• scarv/scarv-soc houses the System on Chip (SoC) implementation: using the processor core as a central component, the SoC delivers functionality aligned with a micro-controller class device. More specifically, it adds peripherals including

  • memory (i.e., some RAM),
  • communication (e.g., a UART), and
  • randomness generation.

Quickstart (with more detail in the wiki)

1. Install any associated pre-requisites, e.g.,

   • a modern LaTeX distribution, such as TeX Live, including any required packages.

2. Execute

   git clone https://github.com/scarv/scarv.git ./scarv
   cd ./scarv
   git submodule update --init --recursive
   source ./bin/conf.sh

   to clone and initialise the repository, then configure the environment; for example, you should find that the environment variable REPO_HOME is set appropriately.

3. Use targets in the top-level Makefile to drive a set of common tasks, e.g.,

   Command	Description
   make build-doc	build the LaTeX-based documentation
   make spotless	remove everything built in ${REPO_HOME}/build

Questions?

• read the wiki,
• raise an issue,
• raise a pull request,
• drop us an email.

Acknowledgements

This work has been supported in part by EPSRC via grant EP/R012288/1 (under the RISE programme).