Example of recursive prover

examples/Cargo.toml

@@ -31,6 +31,9 @@ members = [
   "ssz-withdrawals/script",
   "tendermint/program",
   "tendermint/script",
+  "recursive/lib",
+  "recursive/program",
+  "recursive/script",
 ]
 resolver = "2"
 
@@ -76,4 +79,4 @@ substrate-bn = { git = "https://github.com/sp1-patches/bn", tag = "patch-0.6.0-s
 bls12_381 = { git = "https://github.com/sp1-patches/bls12_381", tag = "patch-0.8.0-sp1-4.0.0" }
 
 # todo!(n) remove
-sp1-lib = { path = "../crates/zkvm/lib" }
+sp1-lib = { path = "../crates/zkvm/lib" }

examples/recursive/lib/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "recursive-lib"
+version = "1.1.0"
+edition = "2021"
+publish = false 
+
+[dependencies]
+sha2 = "0.10.8"
+sp1-zkvm = { path = "../../../crates/zkvm/entrypoint", features = ["verify"] }
+serde = { workspace = true }

examples/recursive/lib/src/lib.rs

@@ -0,0 +1,41 @@
+pub mod utils;
+
+use serde::{Deserialize, Serialize};
+use crate::utils::sha256_hash;
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub struct CircuitInput {
+    pub public_input_hash: [u8; 32],
+    pub public_value: u32,
+    pub private_value: u32,
+}
+
+impl CircuitInput {
+    pub fn new(public_input_hash: [u8; 32], public_value: u32, private_value: u32) -> Self {
+        Self {
+            public_input_hash,
+            public_value,
+            private_value,
+        }
+    }
+}
+
+/// Given `x_0, x_1, x_2, ...., x_{n - 1}` as public values, we want to know `x_0^3 + x_1^3 +
+/// x_2^3 + ...+ x_{n - 1}^3`
+/// 
+/// core function, say `f(y, x) = y + x^3`, where:
+/// 1) y, is the accumulation result, marked as private value
+/// 2) x, is the public value
+pub fn acc_cubic(public_value: u32, private_value: u32) -> u32 {
+    private_value.wrapping_add(public_value.wrapping_mul(public_value).wrapping_mul(public_value))
+}
+
+/// Verify last prover's proof with two public values:
+/// 1) public_input_hash, which is a recursive hash of all public values of acc_cubic `f(y, x)`
+/// 2) y, last prover's accumulated result 
+pub fn verify_proof(vkey_hash: &[u32; 8], public_input_hash: &[u8; 32], private_value: u32) {
+    let mut bytes = Vec::with_capacity(36);
+    bytes.extend_from_slice(public_input_hash);
+    bytes.extend_from_slice(&private_value.to_le_bytes());
+    sp1_zkvm::lib::verify::verify_sp1_proof(vkey_hash, &sha256_hash(&bytes));
+}

examples/recursive/lib/src/utils.rs

@@ -0,0 +1,16 @@
+use sha2::{Digest, Sha256};
+
+pub trait AsLittleEndianBytes {
+    fn to_little_endian(self) -> Self;
+}
+
+impl<const N: usize> AsLittleEndianBytes for [u8; N] {
+    fn to_little_endian(mut self) -> Self {
+        self.reverse();
+        self
+    }
+}
+
+pub fn sha256_hash(bytes: &[u8]) -> [u8; 32] {
+    Sha256::digest(bytes).into()
+}

examples/recursive/program/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+version = "0.1.0"
+name = "recursive-program"
+edition = "2021"
+publish = false
+
+[dependencies]
+sp1-zkvm = { path = "../../../crates/zkvm/entrypoint", features = ["verify"] }
+recursive-lib = { path = "../lib" }