Zolt

A Zig zkVM prover that generates proofs verifiable by the unmodified upstream a16z/jolt verifier — no patched fork needed. Zero dependencies, zero FFI — all cryptography (field arithmetic, pairings, MSM, polynomial commitments) is implemented from scratch using only the Zig standard library.

WARNING: This project is experimental and has not been audited. Do not use in production.

Quick Start

# Build Zolt
zig build -Doptimize=ReleaseFast

# Generate a proof
./zig-out/bin/zolt prove examples/fibonacci.elf -o /tmp/proof.bin --export-preprocessing /tmp/preproc.bin

# Verify with upstream Jolt verifier
cargo run --release --manifest-path jolt-verifier/Cargo.toml -- \
  --proof /tmp/proof.bin --preprocessing /tmp/preproc.bin

CLI Reference

zolt prove [options] <elf>

Generate a ZK proof for a RISC-V ELF binary.

Flag	Description
-o, --output FILE	Save proof to FILE (required)
--export-preprocessing FILE	Export Jolt-compatible preprocessing data
--srs PATH	Use Dory SRS from PATH
--input-hex HEX	Set program input as hex bytes

zolt run [options] <elf>

Run a RISC-V ELF binary in the emulator.

Flag	Description
--regs	Show final register state
--trace	Show execution trace
--max N	Max trace entries to display (default: 100)
--input FILE	Load input bytes from FILE
--input-hex HEX	Set input as hex bytes

zolt help / zolt version

Show help or version information.

Example Programs

All 8 example programs produce valid proofs verified by the upstream Jolt verifier:

Program	Description	Expected Result
fibonacci.elf	Compute Fibonacci(10)	55
factorial.elf	Compute 10!	3628800
bitwise.elf	AND, OR, XOR, shifts	-
collatz.elf	Collatz sequence for n=27	111 steps
primes.elf	Count primes < 100	25
sum.elf	Sum of 1..100	5050
gcd.elf	GCD using div/rem	63
signed.elf	Signed arithmetic ops	-39

Building Examples

Requires a RISC-V toolchain (e.g., riscv32-unknown-elf-gcc):

cd examples
make all

Benchmarks

Compared against Jolt (Rust) on a Hetzner CPX41 — 8 vCPU AMD EPYC (Zen 2), 16 GB RAM, Ubuntu 22.04.

Program	Trace	Jolt (ms)	Zolt (ms)	Ratio
fibonacci	256	1240.01	929.33	0.75x
factorial	256	1150.95	1027.77	0.89x
bitwise	512	1351.32	1475.52	1.09x
collatz	2048	1567.96	2541.66	1.62x
primes	2048	1464.57	3443.07	2.35x
sum	256	1260.56	953.11	0.76x
gcd	256	1271.58	1427.87	1.12x
signed	256	1323.29	976.55	0.74x
primes_large	65536	2541.32	30773.29	12.11x

Upstream Compatibility

The jolt-verifier/ crate is pinned to upstream commit 2e05fe88. This is the version all 8 programs are verified against. Updating to a newer upstream commit may require adjustments if the verification protocol changes.

Project Structure

zolt/
├── build.zig / build.zig.zon
├── examples/              # Pre-built RISC-V ELF binaries + C sources
├── jolt-verifier/         # Standalone upstream Jolt verifier (Rust)
└── src/
    ├── main.zig           # CLI
    ├── field/             # BN254 scalar field arithmetic
    ├── poly/              # Polynomials + commitment schemes (HyperKZG, Dory)
    ├── subprotocols/      # Sumcheck protocol
    ├── msm/               # Multi-scalar multiplication (Pippenger)
    ├── transcripts/       # Fiat-Shamir (Blake2b)
    ├── host/              # ELF loader
    ├── tracer/            # RISC-V emulator
    └── zkvm/              # Core proving logic
        ├── jolt_prover.zig       # 7-stage Jolt-compatible prover
        ├── jolt_types.zig        # Proof types, sumcheck IDs
        ├── jolt_serialization.zig
        ├── preprocessing.zig
        ├── spartan/       # Spartan R1CS prover
        ├── shout/         # Shout lookup argument
        ├── r1cs/          # R1CS constraints
        ├── bytecode/      # Bytecode handling
        ├── instruction/   # RISC-V instruction decoder
        ├── ram/           # Memory checking
        └── registers/     # Register file

Prerequisites

• Zig 0.15.0+ — build and run Zolt
• Rust toolchain — build jolt-verifier/ for proof verification
• RISC-V toolchain — build example C programs (pre-built ELFs included)

License

MIT