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}/doc houses
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}/rtl houses
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/scarv specifically houses such an implementation: the SCARV processor
core (and associated SoC) offer an integrated implementation of
components from the entire SCARV project, XCrypto included.
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_HOME environment variable is set appropriately.
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 clone-toolchain | clone the tool-chain |
make build-toolchain | build the tool-chain |
make doxygen | build the Doxygen-based documentation |
make spotless | remove everything built in ${REPO_HOME}/build |
This work has been supported in part
by EPSRC via grant EP/R012288/1 (under the RISE programme).