feat(avm)!: include length in bytecode hash (#11425)

Looks like it's easier to constrain the length of bytecode in the avm if
we just include it in the hash computation

Author: IlyasRidhuan

barretenberg/cpp/src/barretenberg/crypto/poseidon2/c_bind.cpp

@@ -53,8 +53,8 @@ WASM_EXPORT void poseidon2_hash_accumulate(fr::vec_in_buf inputs_buffer, fr::out
     std::vector<fr> to_hash;
     read(inputs_buffer, to_hash);
     const size_t numHashes = to_hash.size();
-    fr result = 0;
-    size_t count = 0;
+    fr result = to_hash[0];
+    size_t count = 1;
     while (count < numHashes) {
         result = crypto::Poseidon2<crypto::Poseidon2Bn254ScalarFieldParams>::hash({ to_hash[count], result });
         ++count;

barretenberg/cpp/src/barretenberg/vm/avm/trace/bytecode_trace.cpp

@@ -80,8 +80,9 @@ std::vector<FF> AvmBytecodeTraceBuilder::encode_bytecode(const std::vector<uint8
 // Compute the public bytecode commitment from a given contract bytecode
 FF AvmBytecodeTraceBuilder::compute_public_bytecode_commitment(const std::vector<uint8_t>& contract_bytes)
 {
+    FF bytecode_length_in_bytes = FF(static_cast<uint64_t>(contract_bytes.size()));
     std::vector<FF> contract_bytecode_fields = encode_bytecode(contract_bytes);
-    FF running_hash = FF::zero();
+    FF running_hash = bytecode_length_in_bytes;
     for (auto& contract_bytecode_field : contract_bytecode_fields) {
         running_hash = poseidon2::hash({ contract_bytecode_field, running_hash });
     }
@@ -114,7 +115,8 @@ void AvmBytecodeTraceBuilder::build_bytecode_hash_columns()
         if (contract_bytecode.bytecode.size() == 0) {
             vinfo("Excluding non-existent contract from bytecode hash columns...");
         } else {
-            FF running_hash = FF::zero();
+            auto bytecode_length_in_bytes = FF(static_cast<uint64_t>(contract_bytecode.bytecode.size()));
+            FF running_hash = bytecode_length_in_bytes;
             auto field_encoded_bytecode = encode_bytecode(contract_bytecode.bytecode);
             // This size is already based on the number of fields
             for (size_t i = 0; i < field_encoded_bytecode.size(); ++i) {

barretenberg/cpp/src/barretenberg/vm2/simulation/lib/contract_crypto.cpp

@@ -27,8 +27,9 @@ FF compute_public_bytecode_commitment(std::span<const uint8_t> bytecode)
         return contract_bytecode_fields;
     };
 
+    FF bytecode_length_in_bytes = FF(static_cast<uint64_t>(bytecode.size()));
     std::vector<FF> contract_bytecode_fields = encode_bytecode(bytecode);
-    FF running_hash = 0;
+    FF running_hash = bytecode_length_in_bytes;
     for (const auto& contract_bytecode_field : contract_bytecode_fields) {
         running_hash = poseidon2::hash({ contract_bytecode_field, running_hash });
     }
@@ -66,4 +67,4 @@ FF compute_contract_address(const ContractInstance& contract_instance)
     return (grumpkin::g1::affine_one * h_fq + contract_instance.public_keys.incoming_viewing_key).x;
 }
 
-} // namespace bb::avm2::simulation
+} // namespace bb::avm2::simulation

noir-projects/noir-contracts/contracts/contract_class_registerer_contract/src/main.nr

@@ -56,7 +56,8 @@ contract ContractClassRegisterer {
             (bytecode_length_in_bytes / 31) + (bytecode_length_in_bytes % 31 != 0) as u32;
         assert(bytecode_length_in_fields < MAX_PACKED_PUBLIC_BYTECODE_SIZE_IN_FIELDS);
 
-        let mut computed_public_bytecode_commitment = 0;
+        // The first value in the running hash is the bytecode length in bytes
+        let mut computed_public_bytecode_commitment = packed_public_bytecode[0];
         // We can hash up to MAX_PACKED_PUBLIC_BYTECODE_SIZE_IN_FIELDS - 1, since the first element is the length
         for i in 0..(MAX_PACKED_PUBLIC_BYTECODE_SIZE_IN_FIELDS - 1) {
             // While we are forced to run the hash MAX_PACKED_PUBLIC_BYTECODE_SIZE_IN_FIELDS times in the circuit,

yarn-project/circuits.js/src/contract/contract_class_id.test.ts

@@ -25,7 +25,7 @@ describe('ContractClass', () => {
       };
 
       expect(computeContractClassId(contractClass).toString()).toMatchInlineSnapshot(
-        `"0x2d5c712c483891d42e5bca539e8516fc52b5b024568ac71e4fe47c0c0157f851"`,
+        `"0x2c3a8b2ad29dd4000cb827e973737bcf57fc072aeaf93ceeef4b4b9eb086cf67"`,
       );
     });
   });

yarn-project/circuits.js/src/contract/contract_class_id.ts

@@ -66,5 +66,5 @@ export function computePublicBytecodeCommitment(packedBytecode: Buffer) {
   const bytecodeLength = Math.ceil(encodedBytecode[0].toNumber() / (Fr.SIZE_IN_BYTES - 1));
   assert(bytecodeLength < MAX_PACKED_PUBLIC_BYTECODE_SIZE_IN_FIELDS, 'Bytecode exceeds maximum deployable size');
 
-  return bytecodeLength == 0 ? new Fr(0) : poseidon2HashAccumulate(encodedBytecode.slice(1, bytecodeLength + 1));
+  return bytecodeLength == 0 ? new Fr(0) : poseidon2HashAccumulate(encodedBytecode.slice(0, bytecodeLength + 1));
 }

yarn-project/noir-protocol-circuits-types/src/__snapshots__/noir_test_gen.test.ts.snap

@@ -4,11 +4,11 @@ exports[`Data generation for noir tests Computes contract info for defaultContra
 "{
   contract_address_salt: 0x000000000000000000000000000000000000000000000000000000000000ddd5,
   artifact_hash: 0x0000000000000000000000000000000000000000000000000000000000003039,
-  public_bytecode_commitment: 0x11fb08be2c55e530172e671f647b16dddf9b66acf42489d0236785d8f7bc8b48,
+  public_bytecode_commitment: 0x2e018d154e7faf1ddf8400a4b3605574e69afc04425f3e662e054dc094fb0428,
   private_functions_root: 0x25d76df45434ec75a83321daf941cfc667ff3a9027942e17105da4f50d1d13f9,
-  address: AztecAddress { inner: 0x29bc2e90ff6ec5f4a7c7f502e368af01eb74131a2eec6320e0e45419cddc7b6d },
-  partial_address: PartialAddress { inner: 0x1a68423cf4f04eaede2b0e93131916b8b7330dae6e8ee202679d12a4eb49cc0b },
-  contract_class_id: ContractClassId { inner: 0x1195b865ef122d75c8c4d6102d536193b69bbb712c85bafcbf7694f52e2d8c36 },
+  address: AztecAddress { inner: 0x0d4379385723a3f96a0d9d59be7dc869e042a9f5b832749039a993e5ee6b91b8 },
+  partial_address: PartialAddress { inner: 0x0b419abfd8ca509592b671ed9808138dced1df38835cbf3b3b693ad71623c90d },
+  contract_class_id: ContractClassId { inner: 0x23b90310794d8e4ee1f13c0b97b4f5d11ddfa1642ad60e46169c3d3b2c6e03a6 },
   public_keys: PublicKeys { inner: 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 },
   salted_initialization_hash: SaltedInitializationHash { inner: 0x13a939daa511233e5446905ed2cadbee14948fa75df183b53b5c14b612bffe88 },
   deployer: AztecAddress { inner: 0x0000000000000000000000000000000000000000000000000000000000000000 }
@@ -19,11 +19,11 @@ exports[`Data generation for noir tests Computes contract info for parentContrac
 "{
   contract_address_salt: 0x0000000000000000000000000000000000000000000000000000000000001618,
   artifact_hash: 0x00000000000000000000000000000000000000000000000000000000000004bc,
-  public_bytecode_commitment: 0x1c5009dd5e8baedc8dfb2e801c9f97361b1ae152ff52f82104119c476b369bef,
+  public_bytecode_commitment: 0x258ed5ce21c3a9c15a1c6108ef0e759bb0617f2b505b8d64e927027d30e71791,
   private_functions_root: 0x1228b39ba6702af03e595300e8484c6373f00790d0148cc3d4ff0fd1c778a83a,
-  address: AztecAddress { inner: 0x2749b685f752f6dfe1d4e532fc036839004926b7c18abf1a4f69ddf97d62f40e },
-  partial_address: PartialAddress { inner: 0x1c30ee02dcd41bcdfc5191dc36ccaae15cdc7e1fc6bd8a0cbe1baeaf1335a771 },
-  contract_class_id: ContractClassId { inner: 0x24f1b8df215c10ee7edd213b439c8f8e99198a802a3e1e41597b6554b17049a3 },
+  address: AztecAddress { inner: 0x0907b0edaac863b283132ee3a4781395ace64ff8cec244f1c5235e88c320cca1 },
+  partial_address: PartialAddress { inner: 0x00906eed7cc361cc78056365c5ddbb94fd8fa05c5fed118bd4033585914cda92 },
+  contract_class_id: ContractClassId { inner: 0x1ffddcc4c6d113ae695384e3bae42cb0c4c6d8ba7edbb80c8c23848b55cd37f3 },
   public_keys: PublicKeys { inner: 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 },
   salted_initialization_hash: SaltedInitializationHash { inner: 0x24bd6ac7a182e2cf25e437c72f53544ef81dfd97d9afee23abb07a638e7be749 },
   deployer: AztecAddress { inner: 0x0000000000000000000000000000000000000000000000000000000000000000 }

yarn-project/protocol-contracts/src/class-registerer/contract_class_registered_event.test.ts

@@ -15,7 +15,7 @@ describe('ContractClassRegisteredEvent', () => {
     expect(event.artifactHash.toString()).toEqual('0x072dce903b1a299d6820eeed695480fe9ec46658b1101885816aed6dd86037f0');
     expect(event.packedPublicBytecode.length).toEqual(27090);
     expect(computePublicBytecodeCommitment(event.packedPublicBytecode).toString()).toEqual(
-      '0x0378491b34825cd67d1e13e140bbc80f2cd3a9b52171ea577f8f11620d4198ba',
+      '0x1d7d509f736d09975b88d01b5779a6f52e70905ba9294776d4881e811e6c1e9f',
     );
   });
 });