node: Update plonk key sizes for the Mint circuit.

example/tx.rs

@@ -129,9 +129,8 @@ fn main() -> Result<()> {
 
     let keypair = Keypair::random(&mut OsRng);
 
-    const K: u32 = 11;
-    let mint_vk = VerifyingKey::build(K, &MintContract::default());
-    let burn_vk = VerifyingKey::build(K, &BurnContract::default());
+    let mint_vk = VerifyingKey::build(8, &MintContract::default());
+    let burn_vk = VerifyingKey::build(11, &BurnContract::default());
 
     let mut state = MemoryState {
         tree: BridgeTree::<MerkleNode, MERKLE_DEPTH>::new(100),
@@ -162,8 +161,8 @@ fn main() -> Result<()> {
         }],
     };
 
-    let mint_pk = ProvingKey::build(K, &MintContract::default());
-    let burn_pk = ProvingKey::build(K, &BurnContract::default());
+    let mint_pk = ProvingKey::build(8, &MintContract::default());
+    let burn_pk = ProvingKey::build(11, &BurnContract::default());
     let tx = builder.build(&mint_pk, &burn_pk)?;
 
     tx.verify(&state.mint_vk, &state.burn_vk)?;

src/node/client.rs

@@ -226,7 +226,7 @@ impl Client {
 
     fn build_mint_pk() -> ProvingKey {
         debug!("Building proving key for MintContract");
-        ProvingKey::build(9, &MintContract::default())
+        ProvingKey::build(8, &MintContract::default())
     }
 
     fn build_burn_pk() -> ProvingKey {

src/node/state.rs

@@ -243,7 +243,7 @@ impl ProgramState for State {
 
 fn build_mint_vk() -> VerifyingKey {
     debug!("Building verifying key for MintContract");
-    VerifyingKey::build(11, &MintContract::default())
+    VerifyingKey::build(8, &MintContract::default())
 }
 
 fn build_burn_vk() -> VerifyingKey {