proof context / external nullifier generation

walletkit-core/Cargo.toml

@@ -15,6 +15,7 @@ crate-type = ["lib", "staticlib", "cdylib"]
 name = "walletkit_core"
 
 [dependencies]
+alloy-core = { version = "0.8.12", default-features = false, features = ["sol-types"] }
 hex = "0.4.3"
 ruint = { version = "1.12.3", default-features = false, features = ["alloc"] }
 semaphore = { git = "https://github.com/worldcoin/semaphore-rs", rev = "accb14b", features = ["depth_30"] }

walletkit-core/src/identity.rs

@@ -28,7 +28,7 @@ impl Identity {
     /// [Protocol Reference](https://docs.semaphore.pse.dev/V2/technical-reference/circuits#nullifier-hash).
     #[must_use]
     pub fn generate_nullifier_hash(&self, context: &Context) -> U256Wrapper {
-        generate_nullifier_hash(&self.0, context.external_nullifier).into()
+        generate_nullifier_hash(&self.0, context.external_nullifier.into()).into()
     }
 }
 
@@ -39,7 +39,7 @@ mod tests {
     #[test]
     fn test() {
         let identity = Identity::new(b"not_a_real_secret");
-        let context = Context::new(b"app_id", b"action");
+        let context = Context::new(b"app_id", None);
         let nullifier_hash = identity.generate_nullifier_hash(&context);
         println!("{}", nullifier_hash.to_hex_string());
     }

walletkit-core/src/proof.rs

@@ -1,19 +1,107 @@
-use ruint::aliases::U256;
+use alloy_core::sol_types::SolValue;
 use semaphore::hash_to_field;
 
+use crate::u256::U256Wrapper;
+
 #[derive(Clone, PartialEq, Eq, Debug, uniffi::Object)]
 pub struct Context {
-    pub external_nullifier: U256,
+    pub external_nullifier: U256Wrapper,
 }
 
 #[uniffi::export]
 impl Context {
     #[must_use]
     #[uniffi::constructor]
-    pub fn new(app_id: &[u8], action: &[u8]) -> Self {
-        let external_nullifier = hash_to_field(app_id);
-        dbg!(&action);
-        // TODO: handle action properly
+    pub fn new(app_id: &[u8], action: Option<Vec<u8>>) -> Self {
+        let mut pre_image = hash_to_field(app_id).abi_encode_packed();
+
+        if let Some(action) = action {
+            pre_image.extend_from_slice(&action);
+        }
+
+        let external_nullifier = hash_to_field(&pre_image).into();
+
         Self { external_nullifier }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use alloy_core::primitives::address;
+    use ruint::{aliases::U256, uint};
+
+    use super::*;
+
+    #[test]
+    fn test_external_nullifier_hash_generation_no_action() {
+        let context = Context::new(b"app_369183bd38f1641b6964ab51d7a20434", None);
+        assert_eq!(
+            context.external_nullifier.to_hex_string(),
+            "0x0073e4a6b670e81dc619b1f8703aa7491dc5aaadf75409aba0ac2414014c0227"
+        );
+
+        let context = Context::new(b"app_369183bd38f1641b6964ab51d7a20434", Some(b"".to_vec()));
+        assert_eq!(
+            context.external_nullifier.to_hex_string(),
+            "0x0073e4a6b670e81dc619b1f8703aa7491dc5aaadf75409aba0ac2414014c0227"
+        );
+    }
+
+    /// This test case comes from the real example in the docs.
+    /// Reference: <https://github.com/worldcoin/world-id-docs/blob/main/src/pages/world-id/try.tsx>
+    #[test]
+    fn test_external_nullifier_hash_generation_string_action_staging() {
+        let context = Context::new(
+            b"app_staging_45068dca85829d2fd90e2dd6f0bff997",
+            Some(b"test-action-qli8g".to_vec()),
+        );
+        assert_eq!(
+            context.external_nullifier.to_hex_string(),
+            "0x00d8b157e767dc59faa533120ed0ce34fc51a71937292ea8baed6ee6f4fda866"
+        );
+    }
+
+    #[test]
+    fn test_external_nullifier_hash_generation_string_action() {
+        let context = Context::new(b"app_10eb12bd96d8f7202892ff25f094c803", Some(b"test-123123".to_vec()));
+        assert_eq!(
+            context.external_nullifier.0,
+            // cspell:disable-next-line
+            uint!(0x0065ebab05692ff2e0816cc4c3b83216c33eaa4d906c6495add6323fe0e2dc89_U256)
+        );
+    }
+
+    #[test]
+    fn test_external_nullifier_hash_generation_with_complex_abi_encoded_values() {
+        let custom_action = [
+            address!("541f3cc5772a64f2ba0a47e83236CcE2F089b188").abi_encode_packed(),
+            U256::from(1).abi_encode_packed(),
+            "hello".abi_encode_packed(),
+        ]
+        .concat();
+
+        let context = Context::new(b"app_10eb12bd96d8f7202892ff25f094c803", Some(custom_action));
+        assert_eq!(
+            context.external_nullifier.to_hex_string(),
+            // expected output obtained from Solidity
+            "0x00f974ff06219e8ca992073d8bbe05084f81250dbd8f37cae733f24fcc0c5ffd"
+        );
+    }
+
+    #[test]
+    fn test_external_nullifier_hash_generation_with_complex_abi_encoded_values_staging() {
+        let custom_action = [
+            "world".abi_encode_packed(),
+            U256::from(1).abi_encode_packed(),
+            "hello".abi_encode_packed(),
+        ]
+        .concat();
+
+        let context = Context::new(b"app_staging_45068dca85829d2fd90e2dd6f0bff997", Some(custom_action));
+        assert_eq!(
+            context.external_nullifier.to_hex_string(),
+            // expected output obtained from Solidity
+            "0x005b49f95e822c7c37f4f043421689b11f880e617faa5cd0391803bc9bcc63c0"
+        );
+    }
+}

walletkit-core/src/u256.rs

@@ -9,7 +9,7 @@ use ruint::aliases::U256;
 /// Particularly, when sending proof inputs/outputs as JSON on HTTP requests, the values SHOULD
 /// be represented as padded hex strings from Big Endian bytes.
 #[allow(clippy::module_name_repetitions)]
-#[derive(uniffi::Object, Debug, PartialEq, Eq, Clone)]
+#[derive(uniffi::Object, Debug, PartialEq, Eq, Clone, Copy)]
 pub struct U256Wrapper(pub U256);
 
 #[uniffi::export]