hold for now

consensus/types/src/signed_execution_payload_envelope.rs

@@ -74,6 +74,36 @@ impl<E: EthSpec> SignedExecutionPayloadEnvelope<E> {
             Self::NextFork(signed) => ExecutionPayloadEnvelopeRef::NextFork(&signed.message),
         }
     }
+
+    /// Verify `self.signature`.
+    ///
+    /// The `parent_state` is the post-state of the beacon block with
+    /// block_root = self.message.beacon_block_root
+    pub fn verify_signature(
+        &self,
+        parent_state: &BeaconState<E>,
+        spec: &ChainSpec,
+    ) -> Result<bool, BeaconStateError> {
+        let domain = spec.get_domain(
+            parent_state.current_epoch(),
+            Domain::BeaconBuilder,
+            &parent_state.fork(),
+            parent_state.genesis_validators_root(),
+        );
+        let pubkey = parent_state
+            .validators()
+            .get(self.message().builder_index() as usize)
+            .and_then(|v| {
+                let pk: Option<PublicKey> = v.pubkey.decompress().ok();
+                pk
+            })
+            .ok_or_else(|| {
+                BeaconStateError::UnknownValidator(self.message().builder_index() as usize)
+            })?;
+        let message = self.message().signing_root(domain);
+
+        Ok(self.signature().verify(&pubkey, message))
+    }
 }
 
 impl<'de, E: EthSpec> ContextDeserialize<'de, ForkName> for SignedExecutionPayloadEnvelope<E> {