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A Zero-knowledge Virtual Machine is a virtual-machine that, besides executing programs, also produces a zero-knowledge proof of their execution. It is a more general form of a zkEVM which only executes and proves the execution of Ethereum transactions and contracts on its state trie.
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sp1 is a zkVM written in Rust, developed by the Succinct Labs foundation. It can prove the execution of programs in the
RISC-Vinstruction-set, by generating proofs in either its native format or in Plonk or Groth16. It also provides a library and toolchain to ease the creation of sp1-friendly programs from high-level code written in Rust -
Other popular zkVM’s that operate on RISC-V are (RISC Zero)[https://dev.risczero.com/api/zkvm/] and (Jolt)[https://jolt.a16zcrypto.com/]
| Si | Stage | Description |
|---|---|---|
| 1. | Compile Program | Write a Rust program that uses the sp1-zkvm library to compile the program, while using utilities provided by the library to interact with the virtual-machine including I/O, heap-allocations & system-calls. This step may be done in other language that can compile to RISC-V (which includes all languages that have an LLVM backend), but then the sp1-zkvm library may not be used and linking would have to be done manually. Sample Rust program that will get compiled to RISC-V |
| 2. | Generate Proof of Execution | Invoke the virtual-machine using sp1-sdk to execute the compiled program, which produces its output and a proof of its execution. Before execution, the proving and verifying keys are generated from the program. Sample Rust program that creates the prover-client, makes it generate the proof and then verifies the same proof |
| 3. | Verify Proof of Execution | Verify the execution of the program using its provided proof and verifying key (the inputs provided to the program are not needed for verification) |
Proof Generation
sp1 separates the proof generation process into 4 stages:
- Generate shard proofs which split up and prove the valid execution of a RISC-V program.
- Compress shard proofs into a single shard proof.
- Wrap the shard proof into a SNARK-friendly field.
- Wrap the last shard proof, proven over the SNARK-friendly field, into a PLONK proof