add to book

zokrates_bellperson/src/nova.rs

@@ -251,11 +251,26 @@ mod tests {
         use zokrates_ast::ir::Prog;
         use zokrates_field::PallasField;
 
-        fn test<T: NovaField>(program: Prog<T>, initial_state: Vec<T>, step_privates: Vec<Vec<T>>, expected_final_state: Vec<T>) {
+        fn test<T: NovaField>(
+            program: Prog<T>,
+            initial_state: Vec<T>,
+            step_privates: Vec<Vec<T>>,
+            expected_final_state: Vec<T>,
+        ) {
             let steps_count = step_privates.len();
             let params = generate_public_parameters(program.clone()).unwrap();
-            let proof = prove(&params, program.clone(), initial_state.clone(), step_privates).unwrap().unwrap();
-            assert_eq!(verify(&params, proof, steps_count, initial_state).unwrap(), expected_final_state);
+            let proof = prove(
+                &params,
+                program.clone(),
+                initial_state.clone(),
+                step_privates,
+            )
+            .unwrap()
+            .unwrap();
+            assert_eq!(
+                verify(&params, proof, steps_count, initial_state).unwrap(),
+                expected_final_state
+            );
         }
 
         #[test]
@@ -272,7 +287,12 @@ mod tests {
                 statements: vec![Statement::constraint(Variable::new(0), Variable::public(0))],
             };
 
-            test(program, vec![PallasField::from(0)], vec![vec![]; 3], vec![PallasField::from(0)]);
+            test(
+                program,
+                vec![PallasField::from(0)],
+                vec![vec![]; 3],
+                vec![PallasField::from(0)],
+            );
         }
 
         #[test]
@@ -286,7 +306,12 @@ mod tests {
                 )],
             };
 
-            test(program, vec![PallasField::from(3)], vec![vec![]; 3], vec![PallasField::from(6)]);
+            test(
+                program,
+                vec![PallasField::from(3)],
+                vec![vec![]; 3],
+                vec![PallasField::from(6)],
+            );
         }
 
         #[test]
@@ -346,7 +371,7 @@ mod tests {
                     vec![PallasField::from(2)],
                     vec![PallasField::from(3)],
                 ],
-                vec![PallasField::from(8)]
+                vec![PallasField::from(8)],
             );
         }
 
@@ -367,14 +392,16 @@ mod tests {
                     Parameter::private(Variable::new(3)),
                 ],
                 return_count: 2,
-                statements: vec![Statement::constraint(
-                    LinComb::from(Variable::new(0)) + LinComb::from(Variable::new(2)),
-                    Variable::public(0),
-                ),
-                Statement::constraint(
-                    LinComb::from(Variable::new(1)) + LinComb::from(Variable::new(3)),
-                    Variable::public(1),
-                )],
+                statements: vec![
+                    Statement::constraint(
+                        LinComb::from(Variable::new(0)) + LinComb::from(Variable::new(2)),
+                        Variable::public(0),
+                    ),
+                    Statement::constraint(
+                        LinComb::from(Variable::new(1)) + LinComb::from(Variable::new(3)),
+                        Variable::public(1),
+                    ),
+                ],
             };
 
             test(

zokrates_book/src/SUMMARY.md

@@ -27,6 +27,7 @@
     - [ZIR](toolbox/ir.md)
     - [JSON ABI](toolbox/abi.md)
     - [zokrates.js](toolbox/zokrates_js.md)
+    - [Experimental](toolbox/experimental.md)
 
 - [Examples](examples/index.md)
     - [A SNARK Powered RNG](examples/rng_tutorial.md)

zokrates_book/src/toolbox/experimental.md

@@ -0,0 +1,45 @@
+# Experimental features
+
+ZoKrates supports some experimental features.
+
+## Nova
+
+ZoKrates supports the `nova` proof system using the `bellperson` backend. Nova is accessed with the subcommand `nova`.
+
+### API
+
+To use Nova, programs must have the following signature, for any types `State` and `StepInput`:
+
+```
+def main(public State state, private StepInput step_input) -> State
+```
+
+Then, using Nova lets the user prove many steps of this program, given an initial state.
+
+For example:
+
+```
+{{#include ../../../zokrates_cli/examples/book/nova_step.zok}}
+```
+
+We compile this program using the Pallas curve:
+
+```bash
+zokrates compile -i sum.zok --curve pallas
+```
+
+Then we can prove three iterations as follows:
+
+```bash
+echo "\"0\"" > init.json
+echo "[\"1\", \"7\", \"42\"]" > steps.json
+zokrates nova prove
+```
+
+The proof created at `proof.json` proves the statement `0 + 1 + 7 + 42 == 50`.
+
+### Limitations
+
+- The step circuit must be compiled with `--curve pallas`
+- The resulting recursive proof cannot currently be verified on the EVM
+- The public parameters are currently computed for each proof

zokrates_cli/examples/book/nova_step.zok

@@ -0,0 +1,3 @@
+def main(public field sum, private field element) -> field {
+    return sum + element;
+}