Use prepared verifying key for non-batch Groth16 verification (#3092)

zebra-consensus/src/primitives/groth16.rs

@@ -9,7 +9,7 @@ use std::{
 };
 
 use bellman::{
-    groth16::{batch, prepare_verifying_key, VerifyingKey},
+    groth16::{batch, VerifyingKey},
     VerificationError,
 };
 use bls12_381::Bls12;
@@ -40,31 +40,28 @@ pub use params::{Groth16Parameters, GROTH16_PARAMETERS};
 /// handle.
 pub static SPEND_VERIFIER: Lazy<
     Fallback<Batch<Verifier, Item>, ServiceFn<fn(Item) -> Ready<Result<(), VerificationError>>>>,
-> =
+> = Lazy::new(|| {
-    Lazy::new(|| {
+    Fallback::new(
-        Fallback::new(
+        Batch::new(
-            Batch::new(
+            Verifier::new(&GROTH16_PARAMETERS.sapling.spend.vk),
-                Verifier::new(&GROTH16_PARAMETERS.sapling.spend.vk),
+            super::MAX_BATCH_SIZE,
-                super::MAX_BATCH_SIZE,
+            super::MAX_BATCH_LATENCY,
-                super::MAX_BATCH_LATENCY,
+        ),
-            ),
+        // We want to fallback to individual verification if batch verification
-            // We want to fallback to individual verification if batch verification
+        // fails, so we need a Service to use. The obvious way to do this would
-            // fails, so we need a Service to use. The obvious way to do this would
+        // be to write a closure that returns an async block. But because we
-            // be to write a closure that returns an async block. But because we
+        // have to specify the type of a static, we need to be able to write the
-            // have to specify the type of a static, we need to be able to write the
+        // type of the closure and its return value, and both closures and async
-            // type of the closure and its return value, and both closures and async
+        // blocks have eldritch types whose names cannot be written. So instead,
-            // blocks have eldritch types whose names cannot be written. So instead,
+        // we use a Ready to avoid an async block and cast the closure to a
-            // we use a Ready to avoid an async block and cast the closure to a
+        // function (which is possible because it doesn't capture any state).
-            // function (which is possible because it doesn't capture any state).
+        tower::service_fn(
-            tower::service_fn(
+            (|item: Item| {
-                (|item: Item| {
+                ready(item.verify_single(&GROTH16_PARAMETERS.sapling.spend_prepared_verifying_key))
-                    ready(item.verify_single(&prepare_verifying_key(
+            }) as fn(_) -> _,
-                        &GROTH16_PARAMETERS.sapling.spend.vk,
+        ),
-                    )))
+    )
-                }) as fn(_) -> _,
+});
-            ),
-        )
-    });
 
 /// Global batch verification context for Groth16 proofs of Output statements.
 ///
@@ -93,9 +90,7 @@ pub static OUTPUT_VERIFIER: Lazy<
         // function (which is possible because it doesn't capture any state).
         tower::service_fn(
             (|item: Item| {
-                ready(item.verify_single(&prepare_verifying_key(
+                ready(item.verify_single(&GROTH16_PARAMETERS.sapling.output_prepared_verifying_key))
-                    &GROTH16_PARAMETERS.sapling.output.vk,
-                )))
             }) as fn(_) -> _,
         ),
     )

zebra-consensus/src/primitives/groth16/tests.rs

@@ -62,21 +62,18 @@ where
 #[tokio::test]
 async fn verify_sapling_groth16() {
     // Use separate verifiers so shared batch tasks aren't killed when the test ends (#2390)
-    let mut spend_verifier =
+    let mut spend_verifier = Fallback::new(
-        Fallback::new(
+        Batch::new(
-            Batch::new(
+            Verifier::new(&GROTH16_PARAMETERS.sapling.spend.vk),
-                Verifier::new(&GROTH16_PARAMETERS.sapling.spend.vk),
+            crate::primitives::MAX_BATCH_SIZE,
-                crate::primitives::MAX_BATCH_SIZE,
+            crate::primitives::MAX_BATCH_LATENCY,
-                crate::primitives::MAX_BATCH_LATENCY,
+        ),
-            ),
+        tower::service_fn(
-            tower::service_fn(
+            (|item: Item| {
-                (|item: Item| {
+                ready(item.verify_single(&GROTH16_PARAMETERS.sapling.spend_prepared_verifying_key))
-                    ready(item.verify_single(&prepare_verifying_key(
+            }) as fn(_) -> _,
-                        &GROTH16_PARAMETERS.sapling.spend.vk,
+        ),
-                    )))
+    );
-                }) as fn(_) -> _,
-            ),
-        );
     let mut output_verifier = Fallback::new(
         Batch::new(
             Verifier::new(&GROTH16_PARAMETERS.sapling.output.vk),
@@ -85,9 +82,7 @@ async fn verify_sapling_groth16() {
         ),
         tower::service_fn(
             (|item: Item| {
-                ready(item.verify_single(&prepare_verifying_key(
+                ready(item.verify_single(&GROTH16_PARAMETERS.sapling.output_prepared_verifying_key))
-                    &GROTH16_PARAMETERS.sapling.output.vk,
-                )))
             }) as fn(_) -> _,
         ),
     );
@@ -163,9 +158,7 @@ async fn correctly_err_on_invalid_output_proof() {
         ),
         tower::service_fn(
             (|item: Item| {
-                ready(item.verify_single(&prepare_verifying_key(
+                ready(item.verify_single(&GROTH16_PARAMETERS.sapling.output_prepared_verifying_key))
-                    &GROTH16_PARAMETERS.sapling.output.vk,
-                )))
             }) as fn(_) -> _,
         ),
     );