feat(bb): add ability to write pk to file or stdout (#3335)

A vendor succinct is looking to consume noir, in order to not need to
compile the circuit each time nargo prove is run.

A followup pr will come to allow other flows to consume the pk

barretenberg/acir_tests/flows/all_cmds.sh

@@ -9,6 +9,7 @@ FLAGS="-c $CRS_PATH $VFLAG"
 $BIN gates $FLAGS $BFLAG > /dev/null
 $BIN prove -o proof $FLAGS $BFLAG
 $BIN write_vk -o vk $FLAGS $BFLAG
+$BIN write_pk -o pk $FLAGS $BFLAG
 $BIN verify -k vk -p proof $FLAGS
 
 # Check supplemental functions.

barretenberg/cpp/src/barretenberg/bb/main.cpp

@@ -1,5 +1,6 @@
 #include "barretenberg/dsl/acir_format/acir_format.hpp"
 #include "barretenberg/dsl/types.hpp"
+#include "barretenberg/plonk/proof_system/proving_key/serialize.hpp"
 #include "config.hpp"
 #include "get_bytecode.hpp"
 #include "get_crs.hpp"
@@ -183,7 +184,7 @@ bool verify(const std::string& proof_path, bool recursive, const std::string& vk
  * @param bytecodePath Path to the file containing the serialized circuit
  * @param outputPath Path to write the verification key to
  */
-void writeVk(const std::string& bytecodePath, const std::string& outputPath)
+void write_vk(const std::string& bytecodePath, const std::string& outputPath)
 {
     auto constraint_system = get_constraint_system(bytecodePath);
     auto acir_composer = init(constraint_system);
@@ -199,6 +200,22 @@ void writeVk(const std::string& bytecodePath, const std::string& outputPath)
     }
 }
 
+void write_pk(const std::string& bytecodePath, const std::string& outputPath)
+{
+    auto constraint_system = get_constraint_system(bytecodePath);
+    auto acir_composer = init(constraint_system);
+    auto pk = acir_composer.init_proving_key(constraint_system);
+    auto serialized_pk = to_buffer(*pk);
+
+    if (outputPath == "-") {
+        writeRawBytesToStdout(serialized_pk);
+        vinfo("pk written to stdout");
+    } else {
+        write_file(outputPath, serialized_pk);
+        vinfo("pk written to: ", outputPath);
+    }
+}
+
 /**
  * @brief Writes a Solidity verifier contract for an ACIR circuit to a file
  *
@@ -253,7 +270,7 @@ void contract(const std::string& output_path, const std::string& vk_path)
  * @param vk_path Path to the file containing the serialized verification key
  * @param output_path Path to write the proof to
  */
-void proofAsFields(const std::string& proof_path, std::string const& vk_path, const std::string& output_path)
+void proof_as_fields(const std::string& proof_path, std::string const& vk_path, const std::string& output_path)
 {
     auto acir_composer = init();
     auto vk_data = from_buffer<plonk::verification_key_data>(read_file(vk_path));
@@ -282,7 +299,7 @@ void proofAsFields(const std::string& proof_path, std::string const& vk_path, co
  * @param vk_path Path to the file containing the serialized verification key
  * @param output_path Path to write the verification key to
  */
-void vkAsFields(const std::string& vk_path, const std::string& output_path)
+void vk_as_fields(const std::string& vk_path, const std::string& output_path)
 {
     auto acir_composer = init();
     auto vk_data = from_buffer<plonk::verification_key_data>(read_file(vk_path));
@@ -311,7 +328,7 @@ void vkAsFields(const std::string& vk_path, const std::string& output_path)
  *
  * @param output_path Path to write the information to
  */
-void acvmInfo(const std::string& output_path)
+void acvm_info(const std::string& output_path)
 {
 
     const char* jsonData = R"({
@@ -335,12 +352,12 @@ void acvmInfo(const std::string& output_path)
     }
 }
 
-bool flagPresent(std::vector<std::string>& args, const std::string& flag)
+bool flag_present(std::vector<std::string>& args, const std::string& flag)
 {
     return std::find(args.begin(), args.end(), flag) != args.end();
 }
 
-std::string getOption(std::vector<std::string>& args, const std::string& option, const std::string& defaultValue)
+std::string get_option(std::vector<std::string>& args, const std::string& option, const std::string& defaultValue)
 {
     auto itr = std::find(args.begin(), args.end(), option);
     return (itr != args.end() && std::next(itr) != args.end()) ? *(std::next(itr)) : defaultValue;
@@ -350,7 +367,7 @@ int main(int argc, char* argv[])
 {
     try {
         std::vector<std::string> args(argv + 1, argv + argc);
-        verbose = flagPresent(args, "-v") || flagPresent(args, "--verbose");
+        verbose = flag_present(args, "-v") || flag_present(args, "--verbose");
 
         if (args.empty()) {
             std::cerr << "No command provided.\n";
@@ -359,46 +376,50 @@ int main(int argc, char* argv[])
 
         std::string command = args[0];
 
-        std::string bytecode_path = getOption(args, "-b", "./target/acir.gz");
-        std::string witness_path = getOption(args, "-w", "./target/witness.gz");
-        std::string proof_path = getOption(args, "-p", "./proofs/proof");
-        std::string vk_path = getOption(args, "-k", "./target/vk");
-        CRS_PATH = getOption(args, "-c", "./crs");
-        bool recursive = flagPresent(args, "-r") || flagPresent(args, "--recursive");
+        std::string bytecode_path = get_option(args, "-b", "./target/acir.gz");
+        std::string witness_path = get_option(args, "-w", "./target/witness.gz");
+        std::string proof_path = get_option(args, "-p", "./proofs/proof");
+        std::string vk_path = get_option(args, "-k", "./target/vk");
+        std::string pk_path = get_option(args, "-r", "./target/pk");
+        CRS_PATH = get_option(args, "-c", "./crs");
+        bool recursive = flag_present(args, "-r") || flag_present(args, "--recursive");
 
         // Skip CRS initialization for any command which doesn't require the CRS.
         if (command == "--version") {
             writeStringToStdout(BB_VERSION);
             return 0;
         }
         if (command == "info") {
-            std::string output_path = getOption(args, "-o", "info.json");
-            acvmInfo(output_path);
+            std::string output_path = get_option(args, "-o", "info.json");
+            acvm_info(output_path);
             return 0;
         }
 
         if (command == "prove_and_verify") {
             return proveAndVerify(bytecode_path, witness_path, recursive) ? 0 : 1;
         }
         if (command == "prove") {
-            std::string output_path = getOption(args, "-o", "./proofs/proof");
+            std::string output_path = get_option(args, "-o", "./proofs/proof");
             prove(bytecode_path, witness_path, recursive, output_path);
         } else if (command == "gates") {
             gateCount(bytecode_path);
         } else if (command == "verify") {
             return verify(proof_path, recursive, vk_path) ? 0 : 1;
         } else if (command == "contract") {
-            std::string output_path = getOption(args, "-o", "./target/contract.sol");
+            std::string output_path = get_option(args, "-o", "./target/contract.sol");
             contract(output_path, vk_path);
         } else if (command == "write_vk") {
-            std::string output_path = getOption(args, "-o", "./target/vk");
-            writeVk(bytecode_path, output_path);
+            std::string output_path = get_option(args, "-o", "./target/vk");
+            write_vk(bytecode_path, output_path);
+        } else if (command == "write_pk") {
+            std::string output_path = get_option(args, "-o", "./target/pk");
+            write_pk(bytecode_path, output_path);
         } else if (command == "proof_as_fields") {
-            std::string output_path = getOption(args, "-o", proof_path + "_fields.json");
-            proofAsFields(proof_path, vk_path, output_path);
+            std::string output_path = get_option(args, "-o", proof_path + "_fields.json");
+            proof_as_fields(proof_path, vk_path, output_path);
         } else if (command == "vk_as_fields") {
-            std::string output_path = getOption(args, "-o", vk_path + "_fields.json");
-            vkAsFields(vk_path, output_path);
+            std::string output_path = get_option(args, "-o", vk_path + "_fields.json");
+            vk_as_fields(vk_path, output_path);
         } else {
             std::cerr << "Unknown command: " << command << "\n";
             return 1;

barretenberg/cpp/src/barretenberg/dsl/acir_proofs/acir_composer.cpp

@@ -4,6 +4,7 @@
 #include "barretenberg/dsl/acir_format/acir_format.hpp"
 #include "barretenberg/dsl/acir_format/recursion_constraint.hpp"
 #include "barretenberg/dsl/types.hpp"
+#include "barretenberg/plonk/proof_system/proving_key/proving_key.hpp"
 #include "barretenberg/plonk/proof_system/proving_key/serialize.hpp"
 #include "barretenberg/plonk/proof_system/verification_key/sol_gen.hpp"
 #include "barretenberg/plonk/proof_system/verification_key/verification_key.hpp"
@@ -30,12 +31,14 @@ void AcirComposer::create_circuit(acir_format::acir_format& constraint_system)
     vinfo("gates: ", builder_.get_total_circuit_size());
 }
 
-void AcirComposer::init_proving_key(acir_format::acir_format& constraint_system)
+std::shared_ptr<proof_system::plonk::proving_key> AcirComposer::init_proving_key(
+    acir_format::acir_format& constraint_system)
 {
     create_circuit(constraint_system);
     acir_format::Composer composer;
     vinfo("computing proving key...");
     proving_key_ = composer.compute_proving_key(builder_);
+    return proving_key_;
 }
 
 std::vector<uint8_t> AcirComposer::create_proof(acir_format::acir_format& constraint_system,

barretenberg/cpp/src/barretenberg/dsl/acir_proofs/acir_composer.hpp

@@ -14,7 +14,7 @@ class AcirComposer {
 
     void create_circuit(acir_format::acir_format& constraint_system);
 
-    void init_proving_key(acir_format::acir_format& constraint_system);
+    std::shared_ptr<proof_system::plonk::proving_key> init_proving_key(acir_format::acir_format& constraint_system);
 
     std::vector<uint8_t> create_proof(acir_format::acir_format& constraint_system,
                                       acir_format::WitnessVector& witness,

barretenberg/cpp/src/barretenberg/dsl/acir_proofs/c_bind.cpp

@@ -6,6 +6,7 @@
 #include "barretenberg/common/serialize.hpp"
 #include "barretenberg/common/slab_allocator.hpp"
 #include "barretenberg/dsl/acir_format/acir_format.hpp"
+#include "barretenberg/plonk/proof_system/proving_key/serialize.hpp"
 #include "barretenberg/plonk/proof_system/verification_key/verification_key.hpp"
 #include "barretenberg/srs/global_crs.hpp"
 #include <cstdint>
@@ -73,6 +74,15 @@ WASM_EXPORT void acir_get_verification_key(in_ptr acir_composer_ptr, uint8_t** o
     *out = to_heap_buffer(to_buffer(*vk));
 }
 
+WASM_EXPORT void acir_get_proving_key(in_ptr acir_composer_ptr, uint8_t const* acir_vec, uint8_t** out)
+{
+    auto acir_composer = reinterpret_cast<acir_proofs::AcirComposer*>(*acir_composer_ptr);
+    auto constraint_system = acir_format::circuit_buf_to_acir_format(from_buffer<std::vector<uint8_t>>(acir_vec));
+    auto pk = acir_composer->init_proving_key(constraint_system);
+    // We flatten to a vector<uint8_t> first, as that's how we treat it on the calling side.
+    *out = to_heap_buffer(to_buffer(*pk));
+}
+
 WASM_EXPORT void acir_verify_proof(in_ptr acir_composer_ptr,
                                    uint8_t const* proof_buf,
                                    bool const* is_recursive,

barretenberg/cpp/src/barretenberg/dsl/acir_proofs/c_bind.hpp

@@ -38,6 +38,8 @@ WASM_EXPORT void acir_init_verification_key(in_ptr acir_composer_ptr);
 
 WASM_EXPORT void acir_get_verification_key(in_ptr acir_composer_ptr, uint8_t** out);
 
+WASM_EXPORT void acir_get_proving_key(in_ptr acir_composer_ptr, uint8_t const* acir_vec, uint8_t** out);
+
 WASM_EXPORT void acir_verify_proof(in_ptr acir_composer_ptr,
                                    uint8_t const* proof_buf,
                                    bool const* is_recursive,

barretenberg/ts/src/barretenberg_api/index.ts

@@ -381,6 +381,18 @@ export class BarretenbergApi {
     return out[0];
   }
 
+  async acirGetProvingKey(acirComposerPtr: Ptr, constraintSystemBuf: Uint8Array): Promise<Uint8Array> {
+    const inArgs = [acirComposerPtr, constraintSystemBuf].map(serializeBufferable);
+    const outTypes: OutputType[] = [BufferDeserializer()];
+    const result = await this.wasm.callWasmExport(
+      'acir_get_proving_key',
+      inArgs,
+      outTypes.map(t => t.SIZE_IN_BYTES),
+    );
+    const out = result.map((r, i) => outTypes[i].fromBuffer(r));
+    return out[0];
+  }
+
   async acirVerifyProof(acirComposerPtr: Ptr, proofBuf: Uint8Array, isRecursive: boolean): Promise<boolean> {
     const inArgs = [acirComposerPtr, proofBuf, isRecursive].map(serializeBufferable);
     const outTypes: OutputType[] = [BoolDeserializer()];

barretenberg/ts/src/main.ts

@@ -219,6 +219,25 @@ export async function writeVk(bytecodePath: string, crsPath: string, outputPath:
   }
 }
 
+export async function writePk(bytecodePath: string, crsPath: string, outputPath: string) {
+  const { api, acirComposer } = await init(bytecodePath, crsPath);
+  try {
+    debug('initing proving key...');
+    const bytecode = getBytecode(bytecodePath);
+    const pk = await api.acirGetProvingKey(acirComposer, bytecode);
+
+    if (outputPath === '-') {
+      process.stdout.write(pk);
+      debug(`pk written to stdout`);
+    } else {
+      writeFileSync(outputPath, pk);
+      debug(`pk written to: ${outputPath}`);
+    }
+  } finally {
+    await api.destroy();
+  }
+}
+
 export async function proofAsFields(proofPath: string, vkPath: string, outputPath: string) {
   const { api, acirComposer } = await initLite();
 
@@ -347,6 +366,16 @@ program
     await writeVk(bytecodePath, crsPath, outputPath);
   });
 
+program
+  .command('write_pk')
+  .description('Output proving key.')
+  .option('-b, --bytecode-path <path>', 'Specify the bytecode path', './target/acir.gz')
+  .requiredOption('-o, --output-path <path>', 'Specify the path to write the key')
+  .action(async ({ bytecodePath, outputPath, crsPath }) => {
+    handleGlobalOptions();
+    await writePk(bytecodePath, crsPath, outputPath);
+  });
+
 program
   .command('proof_as_fields')
   .description('Return the proof as fields elements')