CL: expand scope of nullifier proof to an "input proof" (#106)

* cl: nullifier proof -> input proof; add death_cm to input proof

* cl: add death_cm to cl::Input commitment

* cl/ledger: prove_input_nullifier -> prove_input

cl/cl/src/balance.rs

@@ -7,10 +7,10 @@ lazy_static! {
     static ref PEDERSON_COMMITMENT_BLINDING_POINT: RistrettoPoint = crate::crypto::hash_to_curve(b"NOMOS_CL_PEDERSON_COMMITMENT_BLINDING");
 }
 
-#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
 pub struct Balance(pub RistrettoPoint);
 
-#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
 pub struct BalanceWitness {
     pub value: u64,
     pub unit: RistrettoPoint,
@@ -27,7 +27,7 @@ impl BalanceWitness {
     pub fn new(value: u64, unit: impl Into<String>, blinding: Scalar) -> Self {
         Self {
             value,
-            unit: unit_point(&unit.into()).into(),
+            unit: unit_point(&unit.into()),
             blinding,
         }
     }
@@ -37,7 +37,7 @@ impl BalanceWitness {
     }
 
     pub fn commit(&self) -> Balance {
-        Balance(balance(self.value, self.unit.into(), self.blinding).into())
+        Balance(balance(self.value, self.unit, self.blinding))
     }
 }
 

cl/cl/src/input.rs

@@ -4,21 +4,20 @@
 /// which on their own may not balance (i.e. \sum inputs != \sum outputs)
 use crate::{
     balance::Balance,
-    note::{NoteCommitment, NoteWitness},
+    note::{DeathCommitment, NoteWitness},
     nullifier::{Nullifier, NullifierNonce, NullifierSecret},
 };
 use rand_core::RngCore;
-// use risc0_groth16::{PublicInputsJson, Verifier};
 use serde::{Deserialize, Serialize};
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Input {
-    pub note_comm: NoteCommitment,
     pub nullifier: Nullifier,
     pub balance: Balance,
+    pub death_cm: DeathCommitment,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 pub struct InputWitness {
     pub note: NoteWitness,
     pub nf_sk: NullifierSecret,
@@ -36,9 +35,9 @@ impl InputWitness {
 
     pub fn commit(&self) -> Input {
         Input {
-            note_comm: self.note.commit(self.nf_sk.commit(), self.nonce),
             nullifier: Nullifier::new(self.nf_sk, self.nonce),
             balance: self.note.balance(),
+            death_cm: self.note.death_commitment(),
         }
     }
 
@@ -52,11 +51,11 @@ impl InputWitness {
 }
 
 impl Input {
-    pub fn to_bytes(&self) -> [u8; 96] {
-        let mut bytes = [0u8; 96];
-        bytes[..32].copy_from_slice(self.note_comm.as_bytes());
-        bytes[32..64].copy_from_slice(self.nullifier.as_bytes());
-        bytes[64..96].copy_from_slice(&self.balance.to_bytes());
+    pub fn to_bytes(&self) -> [u8; 64] {
+        let mut bytes = [0u8; 64];
+        bytes[..32].copy_from_slice(self.nullifier.as_bytes());
+        bytes[32..64].copy_from_slice(&self.balance.to_bytes());
+        bytes[64..96].copy_from_slice(&self.death_cm.0);
         bytes
     }
 }

cl/cl/src/lib.rs

@@ -12,7 +12,7 @@ pub mod partial_tx;
 pub use balance::{Balance, BalanceWitness};
 pub use bundle::{Bundle, BundleWitness};
 pub use input::{Input, InputWitness};
-pub use note::{NoteCommitment, NoteWitness};
+pub use note::{DeathCommitment, NoteCommitment, NoteWitness};
 pub use nullifier::{Nullifier, NullifierCommitment, NullifierNonce, NullifierSecret};
 pub use output::{Output, OutputWitness};
 pub use partial_tx::{PartialTx, PartialTxWitness, PtxRoot};

cl/cl/src/note.rs

@@ -7,6 +7,18 @@ use crate::{
     nullifier::{NullifierCommitment, NullifierNonce},
 };
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct DeathCommitment(pub [u8; 32]);
+
+pub fn death_commitment(death_constraint: &[u8]) -> DeathCommitment {
+    let mut hasher = Sha256::new();
+    hasher.update(b"NOMOS_CL_DEATH_COMMIT");
+    hasher.update(death_constraint);
+    let death_cm: [u8; 32] = hasher.finalize().into();
+
+    DeathCommitment(death_cm)
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
 pub struct NoteCommitment([u8; 32]);
 
@@ -18,10 +30,10 @@ impl NoteCommitment {
 
 // TODO: Rename Note to NoteWitness and NoteCommitment to Note
 
-#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, Serialize, Deserialize)]
 pub struct NoteWitness {
     pub balance: BalanceWitness,
-    pub death_constraint: Vec<u8>, // serialized verification key of death constraint
+    pub death_constraint: [u8; 32], // death constraint verification key
     pub state: [u8; 32],
 }
 
@@ -34,7 +46,7 @@ impl NoteWitness {
     ) -> Self {
         Self {
             balance: BalanceWitness::random(value, unit, rng),
-            death_constraint: vec![],
+            death_constraint: [0u8; 32],
             state,
         }
     }
@@ -52,7 +64,7 @@ impl NoteWitness {
         hasher.update(self.state);
 
         // COMMIT TO DEATH CONSTRAINT
-        hasher.update(&self.death_constraint);
+        hasher.update(self.death_constraint);
 
         // COMMIT TO NULLIFIER
         hasher.update(nf_pk.as_bytes());
@@ -65,6 +77,10 @@ impl NoteWitness {
     pub fn balance(&self) -> Balance {
         self.balance.commit()
     }
+
+    pub fn death_commitment(&self) -> DeathCommitment {
+        death_commitment(&self.death_constraint)
+    }
 }
 
 #[cfg(test)]

cl/ledger/src/input.rs

@@ -1,50 +1,40 @@
-use proof_statements::nullifier::{NullifierPrivate, NullifierPublic};
+use proof_statements::input::{InputPrivate, InputPublic};
 
 use crate::error::Result;
 
 const MAX_NOTE_COMMS: usize = 2usize.pow(8);
 
 #[derive(Debug, Clone)]
-pub struct InputNullifierProof {
+pub struct InputProof {
     receipt: risc0_zkvm::Receipt,
 }
 
-impl InputNullifierProof {
-    pub fn public(&self) -> Result<NullifierPublic> {
+impl InputProof {
+    pub fn public(&self) -> Result<InputPublic> {
         Ok(self.receipt.journal.decode()?)
     }
 
-    pub fn verify(&self, expected_public_inputs: NullifierPublic) -> bool {
+    pub fn verify(&self, expected_public_inputs: &InputPublic) -> bool {
         let Ok(public_inputs) = self.public() else {
             return false;
         };
 
-        public_inputs == expected_public_inputs
-            && self
-                .receipt
-                .verify(nomos_cl_risc0_proofs::NULLIFIER_ID)
-                .is_ok()
+        &public_inputs == expected_public_inputs
+            && self.receipt.verify(nomos_cl_risc0_proofs::INPUT_ID).is_ok()
     }
 }
 
-pub fn prove_input_nullifier(
-    input: &cl::InputWitness,
-    note_commitments: &[cl::NoteCommitment],
-) -> InputNullifierProof {
-    let output = input.to_output_witness();
+pub fn prove_input(input: cl::InputWitness, note_commitments: &[cl::NoteCommitment]) -> InputProof {
+    let output_cm = input.to_output_witness().commit_note();
+
     let cm_leaves = note_commitment_leaves(note_commitments);
-    let output_cm = output.commit_note();
     let cm_idx = note_commitments
         .iter()
         .position(|c| c == &output_cm)
         .unwrap();
     let cm_path = cl::merkle::path(cm_leaves, cm_idx);
 
-    let secrets = NullifierPrivate {
-        nf_sk: input.nf_sk,
-        output,
-        cm_path,
-    };
+    let secrets = InputPrivate { input, cm_path };
 
     let env = risc0_zkvm::ExecutorEnv::builder()
         .write(&secrets)
@@ -62,7 +52,7 @@ pub fn prove_input_nullifier(
     // This struct contains the receipt along with statistics about execution of the guest
     let opts = risc0_zkvm::ProverOpts::succinct();
     let prove_info = prover
-        .prove_with_opts(env, nomos_cl_risc0_proofs::NULLIFIER_ELF, &opts)
+        .prove_with_opts(env, nomos_cl_risc0_proofs::INPUT_ELF, &opts)
         .unwrap();
 
     println!(
@@ -72,7 +62,7 @@ pub fn prove_input_nullifier(
     );
     // extract the receipt.
     let receipt = prove_info.receipt;
-    InputNullifierProof { receipt }
+    InputProof { receipt }
 }
 
 fn note_commitment_leaves(note_commitments: &[cl::NoteCommitment]) -> [[u8; 32]; MAX_NOTE_COMMS] {
@@ -83,10 +73,9 @@ fn note_commitment_leaves(note_commitments: &[cl::NoteCommitment]) -> [[u8; 32];
 
 #[cfg(test)]
 mod test {
-    use proof_statements::nullifier::NullifierPublic;
     use rand::thread_rng;
 
-    use super::{note_commitment_leaves, prove_input_nullifier};
+    use super::*;
 
     #[test]
     fn test_input_nullifier_prover() {
@@ -94,7 +83,7 @@ mod test {
         let input = cl::InputWitness {
             note: cl::NoteWitness {
                 balance: cl::BalanceWitness::random(32, "NMO", &mut rng),
-                death_constraint: vec![],
+                death_constraint: [0u8; 32],
                 state: [0u8; 32],
             },
             nf_sk: cl::NullifierSecret::random(&mut rng),
@@ -103,24 +92,49 @@ mod test {
 
         let notes = vec![input.to_output_witness().commit_note()];
 
-        let proof = prove_input_nullifier(&input, &notes);
+        let proof = prove_input(input, &notes);
 
-        let expected_public_inputs = NullifierPublic {
+        let expected_public_inputs = InputPublic {
             cm_root: cl::merkle::root(note_commitment_leaves(&notes)),
-            nf: input.commit().nullifier,
+            input: input.commit(),
         };
 
-        assert!(proof.verify(expected_public_inputs));
+        assert!(proof.verify(&expected_public_inputs));
 
-        let wrong_public_inputs = NullifierPublic {
-            cm_root: cl::merkle::root(note_commitment_leaves(&notes)),
-            nf: cl::Nullifier::new(
+        let wrong_public_inputs = [
+            InputPublic {
+                cm_root: cl::merkle::root([cl::merkle::leaf(b"bad_root")]),
+                ..expected_public_inputs
+            },
+            InputPublic {
+                input: cl::Input {
+                    nullifier: cl::Nullifier::new(
                         cl::NullifierSecret::random(&mut rng),
                         cl::NullifierNonce::random(&mut rng),
                     ),
-        };
+                    ..expected_public_inputs.input
+                },
+                ..expected_public_inputs
+            },
+            InputPublic {
+                input: cl::Input {
+                    death_cm: cl::note::death_commitment(b"wrong death vk"),
+                    ..expected_public_inputs.input
+                },
+                ..expected_public_inputs
+            },
+            InputPublic {
+                input: cl::Input {
+                    balance: cl::BalanceWitness::random(32, "NMO", &mut rng).commit(),
+                    ..expected_public_inputs.input
+                },
+                ..expected_public_inputs
+            },
+        ];
 
-        assert!(!proof.verify(wrong_public_inputs));
+        for wrong_input in wrong_public_inputs {
+            assert!(!proof.verify(&wrong_input));
+        }
     }
 
     // ----- The following tests still need to be built. -----

cl/proof_statements/src/input.rs

@@ -0,0 +1,21 @@
+use serde::{Deserialize, Serialize};
+
+/// for public inputs `nf` (nullifier), `root_cm` (root of merkle tree over commitment set) and `death_cm` (commitment to death constraint).
+/// the prover has knowledge of `output = (note, nf_pk, nonce)`, `nf` and `path` s.t. that the following constraints hold
+/// 0. nf_pk = hash(nf_sk)
+/// 1. nf = hash(nonce||nf_sk)
+/// 2. note_cm = output_commitment(output)
+/// 3. verify_merkle_path(note_cm, root, path)
+/// 4. death_cm = death_commitment(note.death_constraint)
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub struct InputPublic {
+    pub cm_root: [u8; 32],
+    pub input: cl::Input,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct InputPrivate {
+    pub input: cl::InputWitness,
+    pub cm_path: Vec<cl::merkle::PathNode>,
+}

cl/proof_statements/src/lib.rs

@@ -1 +1 @@
-pub mod nullifier;
+pub mod input;

cl/proof_statements/src/nullifier.rs

@@ -1,22 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-/// for public input `nf` (nullifier) and `root_cm` (root of merkle tree over commitment set).
-/// the prover has knowledge of `output = (note, nf_pk, nonce)`, `nf` and `path` s.t. that the following constraints hold
-/// 0. nf_pk = hash(nf_sk)
-/// 1. nf = hash(nonce||nf_sk)
-/// 2. note_cm = output_commitment(output)
-/// 3. verify_merkle_path(note_cm, root, path)
-
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
-pub struct NullifierPublic {
-    pub cm_root: [u8; 32],
-    pub nf: cl::Nullifier,
-    // TODO: we need a way to link this statement to a particular input. i.e. prove that the nullifier is actually derived from the input note.
-}
-
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
-pub struct NullifierPrivate {
-    pub nf_sk: cl::NullifierSecret,
-    pub output: cl::OutputWitness,
-    pub cm_path: Vec<cl::merkle::PathNode>,
-}

cl/risc0_proofs/Cargo.toml

@@ -7,5 +7,5 @@ edition = "2021"
 risc0-build = { version = "1.0" }
 
 [package.metadata.risc0]
-methods = ["nullifier"]
+methods = ["input"]
 

cl/risc0_proofs/input/Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "nullifier"
+name = "input"
 version = "0.1.0"
 edition = "2021"
 

cl/risc0_proofs/input/src/main.rs

@@ -0,0 +1,17 @@
+/// Input Proof
+use cl::merkle;
+use proof_statements::input::{InputPrivate, InputPublic};
+use risc0_zkvm::guest::env;
+
+fn main() {
+    let secret: InputPrivate = env::read();
+
+    let out_cm = secret.input.to_output_witness().commit_note();
+    let cm_leaf = merkle::leaf(out_cm.as_bytes());
+    let cm_root = merkle::path_root(cm_leaf, &secret.cm_path);
+
+    env::commit(&InputPublic {
+        input: secret.input.commit(),
+        cm_root,
+    });
+}

cl/risc0_proofs/nullifier/src/main.rs

@@ -1,28 +0,0 @@
-/// Nullifier Proof
-///
-/// Our goal: prove the nullifier nf was derived from a note that had previously been committed to.
-///
-/// More formally, nullifier statement says:
-/// for public input `nf` (nullifier) and `root_cm` (root of merkle tree over commitment set).
-/// the prover has knowledge of `output = (note, nf_pk, nonce)`, `nf` and `path` s.t. that the following constraints hold
-/// 0. nf_pk = hash(nf_sk)
-/// 1. nf = hash(nonce||nf_sk)
-/// 2. note_cm = output_commitment(output)
-/// 3. verify_merkle_path(note_cm, root, path)
-use cl::merkle;
-use cl::nullifier::Nullifier;
-use proof_statements::nullifier::{NullifierPrivate, NullifierPublic};
-use risc0_zkvm::guest::env;
-
-fn main() {
-    let secret: NullifierPrivate = env::read();
-    assert_eq!(secret.output.nf_pk, secret.nf_sk.commit());
-
-    let cm_out = secret.output.commit_note();
-    let cm_leaf = merkle::leaf(cm_out.as_bytes());
-    let cm_root = merkle::path_root(cm_leaf, &secret.cm_path);
-
-    let nf = Nullifier::new(secret.nf_sk, secret.output.nonce);
-
-    env::commit(&NullifierPublic { cm_root, nf });
-}