Acting as a component part of the wider SCARV project, XCrypto is a general-purpose Instruction Set Extension (ISE) for RISC-V that supports software-based cryptographic workloads.
A given cryptographic workload is commonly expected to satisfy a challenging and diverse range of traditional design metrics, including some combination of high-throughput, low-latency, low-footprint, power-efficiency, and high-assurance, while executing in what is potentially an adversarial environment. A large design space of options can be drawn from when developing a concrete implementation: these options span a spectrum, between those entirely based on hardware (e.g., a dedicated IP core) and those entirely based on software. ISEs can be viewed as representing a hybrid option, in the sense they alter a general-purpose processor core with special-purpose hardware and associated instructions; such targeted alterations then help to improve a software-based implementation wrt. some design metric (e.g., latency).
As an ISE, we pitch XCrypto as a solution (vs. the solution) within the wider design space of options. For example, it offers as an alternative to the solution being proposed by the RISC-V cryptography extensions group (see, e.g., their presentation: the design extends the RISC-V vector ISE). The idea is to leverage extensive existing literature and hence experience wrt. cryptographic ISEs (see, e.g., published work at the CHES conference), translating and applying it to RISC-V. Although potentially less performant than alternatives, we expect implementations using XCrypto to be more lightweight and flexible; as a result, we view it as representing an attractive solution in the context of micro-controller class cores.
├── bin - scripts (e.g., environment configuration)
├── build - working directory for build
├── doc - documentation
├── extern - external resources (e.g., submodules)
│ ├── libscarv - submodule: scarv/libscarv
│ ├── riscv-opcodes - submodule: scarv/riscv-opcodes
│ ├── texmf - submodule: scarv/texmf
│ └── wiki - submodule: scarv/xcrypto.wiki
├── pdf - PDFs, e.g., presentation slides
├── rtl - source code for re-usable hardware modules
└── src
├── docker - source code for containers
├── helloworld - source code for example program
├── test - source code for test program(s)
└── toolchain - source code for tool-chain
Note that:
-
${REPO_HOME}/dochouses the XCrypto specification: this document captures the ISE itself, acting as both a) a definition of additional architectural state (e.g., register file and CSRs) and instructions (i.e., their semantics and encoding), and b) a design document. Pre-built versions accompany each releases of XCrypto. -
${REPO_HOME}/rtlhouses a library of re-usable hardware components (e.g., for arithmetic operations), which could be used in an implementation of XCrypto. -
Per the above, the content of this repository is non-specific to an implementation of XCrypto within any given processor core. That said, the associated repository
scarv/scarvspecifically houses such an implementation: the SCARV processor core (and associated SoC) offer an integrated implementation of components from the entire SCARV project, XCrypto included.
Quickstart (with more detail in the wiki)
-
Execute
git clone https://github.com/scarv/xcrypto.git ./xcrypto cd ./xcrypto 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
REPO_HOMEenvironment variable is set appropriately. -
Use targets in the top-level
Makefileto drive a set of common tasks, e.g.,Command Description make build-docbuild the LaTeX-based documentation make clone-toolchainclone the tool-chain make build-toolchainbuild the tool-chain make doxygenbuild the Doxygen-based documentation make spotlessremove everything built in ${REPO_HOME}/build
- read the wiki,
- raise an issue,
- raise a pull request,
- drop us an email.
- Some slides presented at the RISC-V meetup in Bristol, April 2019.
- A poster presented at the RISC-V Workshop in Zurich, June 2019.
This work has been supported in part by EPSRC via grant EP/R012288/1 (under the RISE programme).
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