Merge pull request #116 from zcash/signature-validation

Signature validation APIs

src/bundle.rs

@@ -7,7 +7,7 @@ use crate::{
     note::{ExtractedNoteCommitment, Nullifier, TransmittedNoteCiphertext},
     primitives::redpallas::{self, Binding, SpendAuth},
     tree::Anchor,
-    value::ValueCommitment,
+    value::{ValueCommitTrapdoor, ValueCommitment, ValueSum},
 };
 
 /// An action applied to the global ledger.
@@ -300,6 +300,22 @@ impl<T: Authorization, V> Bundle<T, V> {
     }
 }
 
+impl<T: Authorization, V: Copy + Into<ValueSum>> Bundle<T, V> {
+    /// Returns the transaction binding validating key for this bundle.
+    ///
+    /// This can be used to validate the [`Authorized::binding_signature`] returned from
+    /// [`Bundle::authorization`].
+    pub fn binding_validating_key(&self) -> redpallas::VerificationKey<Binding> {
+        (self
+            .actions
+            .iter()
+            .map(|a| a.cv_net())
+            .sum::<ValueCommitment>()
+            - ValueCommitment::derive(self.value_balance.into(), ValueCommitTrapdoor::zero()))
+        .into_bvk()
+    }
+}
+
 /// Authorizing data for a bundle of actions, ready to be committed to the ledger.
 #[derive(Debug, Clone)]
 pub struct Authorized {

src/primitives/redpallas.rs

@@ -5,6 +5,8 @@ use std::convert::{TryFrom, TryInto};
 use pasta_curves::pallas;
 use rand::{CryptoRng, RngCore};
 
+pub use reddsa::batch;
+
 #[cfg(test)]
 use rand::rngs::OsRng;
 
@@ -108,6 +110,26 @@ impl VerificationKey<SpendAuth> {
     pub fn randomize(&self, randomizer: &pallas::Scalar) -> Self {
         VerificationKey(self.0.randomize(randomizer))
     }
+
+    /// Creates a batch validation item from a `SpendAuth` signature.
+    pub fn create_batch_item<M: AsRef<[u8]>>(
+        &self,
+        sig: Signature<SpendAuth>,
+        msg: &M,
+    ) -> batch::Item<SpendAuth, Binding> {
+        batch::Item::from_spendauth(self.0.into(), sig.0, msg)
+    }
+}
+
+impl VerificationKey<Binding> {
+    /// Creates a batch validation item from a `Binding` signature.
+    pub fn create_batch_item<M: AsRef<[u8]>>(
+        &self,
+        sig: Signature<Binding>,
+        msg: &M,
+    ) -> batch::Item<SpendAuth, Binding> {
+        batch::Item::from_binding(self.0.into(), sig.0, msg)
+    }
 }
 
 /// A RedPallas signature.