Split zkvm trait (Sovereign-Labs#214)

* Split zkvm trait

* Remove hint methods from mockzkvm

* Remove unused Error type from zkvm guest

sdk/src/state_machine/core/mocks.rs

@@ -1,8 +1,8 @@
 use borsh::{BorshDeserialize, BorshSerialize};
 
-use crate::zk::traits::{Matches, ProofTrait, ZkVm};
+use crate::zk::traits::{Matches, ProofTrait, Zkvm};
 
-use super::{traits::Witness, types::ArrayWitness};
+use super::types::ArrayWitness;
 
 #[derive(Debug, Clone, PartialEq, Eq, BorshDeserialize, BorshSerialize)]
 pub struct MockCodeCommitment(pub [u8; 32]);
@@ -32,25 +32,17 @@ impl ProofTrait<MockZkvm> for MockProof {
 
 pub struct MockZkvm(ArrayWitness);
 
-impl ZkVm for MockZkvm {
+impl Zkvm for MockZkvm {
     type CodeCommitment = MockCodeCommitment;
 
     type Proof = MockProof;
 
     type Error = anyhow::Error;
 
-    fn write_to_guest<T: crate::serial::Encode>(&self, hint: T) {
-        self.0.add_hint(hint)
-    }
-
-    fn read_from_host<T: crate::serial::Decode>(&self) -> T {
-        self.0.get_hint()
-    }
-
     fn verify(
         proof: Self::Proof,
         code_commitment: &Self::CodeCommitment,
-    ) -> Result<<<Self as ZkVm>::Proof as crate::zk::traits::ProofTrait<Self>>::Output, Self::Error>
+    ) -> Result<<<Self as Zkvm>::Proof as crate::zk::traits::ProofTrait<Self>>::Output, Self::Error>
     {
         proof.verify(code_commitment)
     }

sdk/src/state_machine/zk/traits.rs

@@ -5,20 +5,28 @@ use borsh::{BorshDeserialize, BorshSerialize};
 use crate::serial::{Decode, Encode};
 
 /// A proof that a program was executed in a zkVM.
-pub trait ZkVm {
+pub trait ZkvmHost: Zkvm {
+    fn write_to_guest<T: Encode>(&self, item: T);
+}
+
+/// A Zk proof system capable of proving and verifying arbitrary Rust code
+pub trait Zkvm {
     type CodeCommitment: Matches<Self::CodeCommitment> + Clone;
     type Proof: ProofTrait<Self>;
     type Error: Debug;
 
-    fn write_to_guest<T: Encode>(&self, item: T);
-    fn read_from_host<T: Decode>(&self) -> T;
     fn verify(
         proof: Self::Proof,
         code_commitment: &Self::CodeCommitment,
-    ) -> Result<<<Self as ZkVm>::Proof as ProofTrait<Self>>::Output, Self::Error>;
+    ) -> Result<<<Self as Zkvm>::Proof as ProofTrait<Self>>::Output, Self::Error>;
+}
+
+/// A proof that a program was executed in a zkVM.
+pub trait ZkvmGuest: Zkvm {
+    fn read_from_host<T: Decode>(&self) -> T;
 }
 
-pub trait ProofTrait<VM: ZkVm + ?Sized> {
+pub trait ProofTrait<VM: Zkvm + ?Sized> {
     type Output: Encode + Decode;
     /// Verify the proof, deserializing the result if successful.
     fn verify(self, code_commitment: &VM::CodeCommitment) -> Result<Self::Output, VM::Error>;
@@ -28,13 +36,13 @@ pub trait Matches<T> {
     fn matches(&self, other: &T) -> bool;
 }
 
-pub enum RecursiveProofInput<Vm: ZkVm, T, Pf: ProofTrait<Vm, Output = T>> {
+pub enum RecursiveProofInput<Vm: Zkvm, T, Pf: ProofTrait<Vm, Output = T>> {
     Base(T),
     Recursive(Pf, std::marker::PhantomData<Vm>),
 }
 
 #[derive(BorshSerialize, BorshDeserialize)]
-pub struct RecursiveProofOutput<Vm: ZkVm, T> {
+pub struct RecursiveProofOutput<Vm: Zkvm, T> {
     pub claimed_method_id: Vm::CodeCommitment,
     pub output: T,
 }