SLotH

An accelerator / codesign for SLH-DSA ("Stateless Hash-Based Digital Signature Standard") as described in FIPS 205 Initial Public Draft from August 2023.

To cite this work, and the related paper, please use:

@misc{sa24sloth,
    author          = {Markku-Juhani O. Saarinen},
    title           = {Accelerating {SLH}-{DSA} by Two Orders of Magnitude with a Single Hash Unit},
    howpublished    = {Fifth {NIST} {PQC} Standardization Conference, April 10-12, 2024, Rockville, Maryland.
                    Updated version, {IACR} ePrint 2024/367},
    url             = {https://eprint.iacr.org/2024/367},
    year            = {2024}
}

Downloading

To clone the repository:

git clone https://github.com/slh-dsa/sloth.git

What's where

sloth
├── slh             # Self-Contained C Implementation of SLH-DSA
├── rtl             # Verilog HDL source code
├── drv             # Accelerator drivers and test code
├── kat             # SLH-DSA Known Answer Test data
├── flow            # Misc files for FPGA and ASIC flows
├── Makefile        # Convenience Makefile for the Accelerator
├── LICENSE
└── README.md

Core SLH-DSA Algorithm in ANSI C

The SLotH accelerator uses a core SLH-DSA algorithm implementation contained in the slh directory. The core implementation is self-contained ANSI C code and should be able to run on pretty much any target. There are no prerequisites except for make and a C compiler.

cd sloth/slh
make test

See slh/README.md for more information.

Verilator Simulation

As a prerequisite for simulation, you'll need:

• Verilator verilog simulator.
• A RISC-V cross-compiler that supports bare-metal targets. You can build a suitable riscv-gnu-toolchain with ./configure --enable-multilib and make newlib.

Both of these may be available as packages for Linux operating systems. The name of your toolchain is set in XCHAIN variable in the Makefile.

To build and run a quick end-to-end test, try:

make veri

After a successful compilation the output should look something like this:

./_build/Vsim_tb

[RESET]    ______        __  __ __
          / __/ /  ___  / /_/ // /  SLotH Accelerator Test 2024/02
         _\ \/ /__/ _ \/ __/ _  /   SLH-DSA / FIPS 205 ipd
        /___/____/\___/\__/_//_/    markku-juhani.saarinen@tuni.fi

[INFO]  === Basic health test ===
[CLK]   778     sha256_compress()
[PASS]  sha256 ( chk= 55F39AFA )
[CLK]   1460    sha512_compress()
[PASS]  sha512 ( chk= 1F59A287 )
[CLK]   1469    keccak_f1600()
[PASS]  shake256 ( chk= 07C97065 )

[INFO]  === Timing / KAT ===
[INFO]  SLH-DSA-SHAKE-128f
[INFO]  kat test count = 0
[CLK]   SLH-DSA-SHAKE-128f 202180 slh_keygen()
[STK]   SLH-DSA-SHAKE-128f 3156 slh_keygen()
[PASS]  sk ( chk= BCA6B2C3 )
[CLK]   SLH-DSA-SHAKE-128f 4923932 slh_sign()
[STK]   SLH-DSA-SHAKE-128f 3940 slh_sign()
[PASS]  sm ( chk= C03DA016 )
[CLK]   SLH-DSA-SHAKE-128f 438901 slh_verify()
[STK]   SLH-DSA-SHAKE-128f 3284 slh_verify()
[PASS]  slh_verify() flip bit = 12389
[PASS]  All tests ok.

You can press key. Press x to exit.
UART 0x78 x


exit()

[**TRAP**]    8145868
- rtl/sim_tb.v:36: Verilog $finish

The readout from this particular execution of SLH-DSA-SHAKE-128f is that KeyGen was 202180 cycles, signing was 4923932 cycles, and verification was 438901 cycles. Furthermore, the self-tests were a PASS; the output matched the Known Answer Tests. Modify the end of test_bench.c to have broader test behavior.

Some other targets

• make prog_cw305: Create and program the bitstream on CW305 (program using ChipWhisperer.)
• make prog_vcu118: Ditto for on VCU118 (program using Vivado's hardware manager.)
• make synth: Run a Nangate45 synthesis and timing (using Yosys/OpenSTA. See flow/yosys-sys.)
• make prof: Profiling (see the per-code line instruction counts in annotated source files created in directory _prof).

Side-Channel Collection

I collect traces from the 20dB low amplified SMA connector (X4). Bit 0 of the GPIO register connects to the SMA connector T13 "CLKOUT" on the board, and this is used as a trigger by test_leak.c. The trace collection and analysis stuff is not included, and anyway works only with my oscilloscope.