chore: Use simple "flat" CRS. (AztecProtocol#3748)

There's no need for us to have such a convoluted set of transcripts for
our CRS in a complicated format. This:
* Uses a single 6GB "flat" CRS with no header data in the ignition s3
bucket, in normalised big-endian form.
* Allows us to use our normal deserialization functions for the fields,
as opposed to specific custom SRS reading code.
* Means we can now download, without complexity, any size CRS we need.
* Changes names to eg `bn254_g1.dat` so doesn't conflict with old cache.
* Get's rid of `size` file and just directly analyses file sizes.

It doesn't address:
* The new grumpkin CRS that arrived yesterday. Someone else can tackle
that one. We also need to figure out how to generate a real one. Another
trusted setup??....

barretenberg/cpp/src/barretenberg/bb/file_io.hpp

@@ -1,29 +1,42 @@
 #pragma once
 #include <barretenberg/common/log.hpp>
+#include <cstdint>
 #include <fstream>
 #include <ios>
 #include <vector>
 
-inline std::vector<uint8_t> read_file(const std::string& filename, size_t bytes = 0)
+inline size_t get_file_size(std::string const& filename)
 {
     // Open the file in binary mode and move to the end.
     std::ifstream file(filename, std::ios::binary | std::ios::ate);
     if (!file) {
-        throw std::runtime_error("Unable to open file: " + filename);
+        return 0;
     }
 
+    file.seekg(0, std::ios::end);
+    return (size_t)file.tellg();
+}
+
+inline std::vector<uint8_t> read_file(const std::string& filename, size_t bytes = 0)
+{
     // Get the file size.
-    std::streamsize size = bytes == 0 ? (std::streamsize)file.tellg() : (std::streamsize)bytes;
+    auto size = get_file_size(filename);
     if (size <= 0) {
         throw std::runtime_error("File is empty or there's an error reading it: " + filename);
     }
 
+    auto to_read = bytes == 0 ? size : bytes;
+
+    std::ifstream file(filename, std::ios::binary);
+    if (!file) {
+        throw std::runtime_error("Unable to open file: " + filename);
+    }
+
     // Create a vector with enough space for the file data.
-    std::vector<uint8_t> fileData((size_t)size);
+    std::vector<uint8_t> fileData(to_read);
 
-    // Go back to the start of the file and read all its contents.
-    file.seekg(0, std::ios::beg);
-    file.read(reinterpret_cast<char*>(fileData.data()), size);
+    // Read all its contents.
+    file.read(reinterpret_cast<char*>(fileData.data()), (std::streamsize)to_read);
 
     return fileData;
 }

barretenberg/cpp/src/barretenberg/bb/get_bn254_crs.cpp

@@ -1,34 +1,17 @@
 #include "get_bn254_crs.hpp"
-
-// Gets the transcript URL from the BARRETENBERG_TRANSCRIPT_URL environment variable, if set.
-// Otherwise returns the default URL.
-namespace {
-std::string get_bn254_transcript_url()
-{
-    const char* ENV_VAR_NAME = "BARRETENBERG_TRANSCRIPT_URL";
-    const std::string DEFAULT_URL = "https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/monomial/transcript00.dat";
-
-    const char* env_url = std::getenv(ENV_VAR_NAME);
-
-    auto environment_variable_exists = ((env_url != nullptr) && *env_url);
-
-    return environment_variable_exists ? std::string(env_url) : DEFAULT_URL;
-}
-} // namespace
+#include "barretenberg/bb/file_io.hpp"
 
 std::vector<uint8_t> download_bn254_g1_data(size_t num_points)
 {
-    size_t g1_start = 28;
-    size_t g1_end = g1_start + num_points * 64 - 1;
+    size_t g1_end = num_points * 64 - 1;
 
-    std::string url = get_bn254_transcript_url();
+    std::string url = "https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/flat/g1.dat";
 
-    std::string command =
-        "curl -s -H \"Range: bytes=" + std::to_string(g1_start) + "-" + std::to_string(g1_end) + "\" '" + url + "'";
+    std::string command = "curl -s -H \"Range: bytes=0-" + std::to_string(g1_end) + "\" '" + url + "'";
 
     auto data = exec_pipe(command);
     // Header + num_points * sizeof point.
-    if (data.size() < g1_end - g1_start) {
+    if (data.size() < g1_end) {
         throw std::runtime_error("Failed to download g1 data.");
     }
 
@@ -37,67 +20,52 @@ std::vector<uint8_t> download_bn254_g1_data(size_t num_points)
 
 std::vector<uint8_t> download_bn254_g2_data()
 {
-    size_t g2_start = 28 + 5040001 * 64;
-    size_t g2_end = g2_start + 128 - 1;
-
-    std::string url = get_bn254_transcript_url();
-
-    std::string command =
-        "curl -s -H \"Range: bytes=" + std::to_string(g2_start) + "-" + std::to_string(g2_end) + "\" '" + url + "'";
-
+    std::string url = "https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/flat/g2.dat";
+    std::string command = "curl -s '" + url + "'";
     return exec_pipe(command);
 }
 
 std::vector<barretenberg::g1::affine_element> get_bn254_g1_data(const std::filesystem::path& path, size_t num_points)
 {
     std::filesystem::create_directories(path);
-    std::ifstream size_file(path / "size");
-    size_t size = 0;
-    if (size_file) {
-        size_file >> size;
-        size_file.close();
-    }
-    if (size >= num_points) {
-        vinfo("using cached crs at: ", path);
-        auto data = read_file(path / "g1.dat", 28 + num_points * 64);
+
+    auto g1_path = path / "bn254_g1.dat";
+    size_t g1_file_size = get_file_size(g1_path);
+
+    if (g1_file_size >= num_points * 64 && g1_file_size % 64 == 0) {
+        vinfo("using cached crs of size ", std::to_string(g1_file_size / 64), " at ", g1_path);
+        auto data = read_file(g1_path, g1_file_size);
         auto points = std::vector<barretenberg::g1::affine_element>(num_points);
-        auto size_of_points_in_bytes = num_points * 64;
-        barretenberg::srs::IO<curve::BN254>::read_affine_elements_from_buffer(
-            points.data(), (char*)data.data(), size_of_points_in_bytes);
+        for (size_t i = 0; i < num_points; ++i) {
+            points[i] = from_buffer<barretenberg::g1::affine_element>(data, i * 64);
+        }
         return points;
     }
 
     vinfo("downloading crs...");
     auto data = download_bn254_g1_data(num_points);
-    write_file(path / "g1.dat", data);
-
-    std::ofstream new_size_file(path / "size");
-    if (!new_size_file) {
-        throw std::runtime_error("Failed to open size file for writing");
-    }
-    new_size_file << num_points;
-    new_size_file.close();
+    write_file(g1_path, data);
 
     auto points = std::vector<barretenberg::g1::affine_element>(num_points);
-    barretenberg::srs::IO<curve::BN254>::read_affine_elements_from_buffer(
-        points.data(), (char*)data.data(), data.size());
+    for (size_t i = 0; i < num_points; ++i) {
+        points[i] = from_buffer<barretenberg::g1::affine_element>(data, i * 64);
+    }
     return points;
 }
 
 barretenberg::g2::affine_element get_bn254_g2_data(const std::filesystem::path& path)
 {
     std::filesystem::create_directories(path);
 
-    try {
-        auto data = read_file(path / "g2.dat");
-        barretenberg::g2::affine_element g2_point;
-        barretenberg::srs::IO<curve::BN254>::read_affine_elements_from_buffer(&g2_point, (char*)data.data(), 128);
-        return g2_point;
-    } catch (std::exception&) {
-        auto data = download_bn254_g2_data();
-        write_file(path / "g2.dat", data);
-        barretenberg::g2::affine_element g2_point;
-        barretenberg::srs::IO<curve::BN254>::read_affine_elements_from_buffer(&g2_point, (char*)data.data(), 128);
-        return g2_point;
+    auto g2_path = path / "bn254_g2.dat";
+    size_t g2_file_size = get_file_size(g2_path);
+
+    if (g2_file_size == 128) {
+        auto data = read_file(g2_path);
+        return from_buffer<barretenberg::g2::affine_element>(data.data());
     }
+
+    auto data = download_bn254_g2_data();
+    write_file(g2_path, data);
+    return from_buffer<barretenberg::g2::affine_element>(data.data());
 }

barretenberg/cpp/src/barretenberg/bb/get_grumpkin_crs.cpp

@@ -45,8 +45,9 @@ std::vector<curve::Grumpkin::AffineElement> get_grumpkin_g1_data(const std::file
         size_file.close();
     }
     if (size >= num_points) {
-        vinfo("using cached crs at: ", path);
-        auto data = read_file(path / "grumpkin_g1.dat", 28 + num_points * 64);
+        auto file = path / "grumpkin_g1.dat";
+        vinfo("using cached crs at: ", file);
+        auto data = read_file(file, 28 + num_points * 64);
         auto points = std::vector<curve::Grumpkin::AffineElement>(num_points);
         auto size_of_points_in_bytes = num_points * 64;
         barretenberg::srs::IO<curve::Grumpkin>::read_affine_elements_from_buffer(

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

@@ -19,7 +19,14 @@
 #include <vector>
 
 using namespace barretenberg;
-std::string CRS_PATH = "./crs";
+
+std::string getHomeDir()
+{
+    char* home = std::getenv("HOME");
+    return home != nullptr ? std::string(home) : "./";
+}
+
+std::string CRS_PATH = getHomeDir() + "/.bb-crs";
 bool verbose = false;
 
 const std::filesystem::path current_path = std::filesystem::current_path();
@@ -441,7 +448,7 @@ int main(int argc, char* argv[])
         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");
+        CRS_PATH = get_option(args, "-c", CRS_PATH);
         bool recursive = flag_present(args, "-r") || flag_present(args, "--recursive");
 
         // Skip CRS initialization for any command which doesn't require the CRS.

barretenberg/cpp/src/barretenberg/ecc/fields/field2_declarations.hpp

@@ -138,4 +138,16 @@ template <class base_field, class Params> struct alignas(32) field2 {
     }
 };
 
+template <typename B, typename base_field, typename Params> void read(B& it, field2<base_field, Params>& value)
+{
+    using serialize::read;
+    read(it, value.c0);
+    read(it, value.c1);
+}
+template <typename B, typename base_field, typename Params> void write(B& buf, field2<base_field, Params> const& value)
+{
+    using serialize::write;
+    write(buf, value.c0);
+    write(buf, value.c1);
+}
 } // namespace barretenberg

barretenberg/cpp/src/barretenberg/srs/c_bind.cpp

@@ -9,18 +9,18 @@
 using namespace barretenberg;
 
 /**
- * WARNING: The SRS is not encoded the same way as all the read/write methods encode.
- * Have to use the old school io functions to parse the buffers.
+ * We are not passed a vector (length prefixed), but the buffer and num points independently.
+ * Saves on having the generate the vector awkwardly calling side after downloading crs.
  */
-WASM_EXPORT void srs_init_srs(uint8_t const* points_buf, uint32_t const* num_points, uint8_t const* g2_point_buf)
+WASM_EXPORT void srs_init_srs(uint8_t const* points_buf, uint32_t const* num_points_buf, uint8_t const* g2_point_buf)
 {
-    auto points = std::vector<g1::affine_element>(ntohl(*num_points));
-    srs::IO<curve::BN254>::read_affine_elements_from_buffer(points.data(), (char*)points_buf, points.size() * 64);
-
-    g2::affine_element g2_point;
-    srs::IO<curve::BN254>::read_affine_elements_from_buffer(&g2_point, (char*)g2_point_buf, 128);
-
-    barretenberg::srs::init_crs_factory(points, g2_point);
+    auto num_points = ntohl(*num_points_buf);
+    auto g1_points = std::vector<g1::affine_element>(num_points);
+    for (size_t i = 0; i < num_points; ++i) {
+        g1_points[i] = from_buffer<barretenberg::g1::affine_element>(points_buf, i * 64);
+    }
+    auto g2_point = from_buffer<g2::affine_element>(g2_point_buf);
+    barretenberg::srs::init_crs_factory(g1_points, g2_point);
 }
 
 /**

barretenberg/ts/src/crs/net_crs.ts

@@ -21,12 +21,11 @@ export class NetCrs {
   }
 
   async downloadG1Data() {
-    const g1Start = 28;
-    const g1End = g1Start + this.numPoints * 64 - 1;
+    const g1End = this.numPoints * 64 - 1;
 
-    const response = await fetch('https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/monomial/transcript00.dat', {
+    const response = await fetch('https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/flat/g1.dat', {
       headers: {
-        Range: `bytes=${g1Start}-${g1End}`,
+        Range: `bytes=0-${g1End}`,
       },
       cache: 'force-cache',
     });
@@ -38,13 +37,7 @@ export class NetCrs {
    * Download the G2 points data.
    */
   async downloadG2Data() {
-    const g2Start = 28 + 5040001 * 64;
-    const g2End = g2Start + 128 - 1;
-
-    const response2 = await fetch('https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/monomial/transcript00.dat', {
-      headers: {
-        Range: `bytes=${g2Start}-${g2End}`,
-      },
+    const response2 = await fetch('https://aztec-ignition.s3.amazonaws.com/MAIN%20IGNITION/flat/g2.dat', {
       cache: 'force-cache',
     });
 

barretenberg/ts/src/crs/node/index.ts

@@ -1,8 +1,9 @@
 import { NetCrs } from '../net_crs.js';
 import { GRUMPKIN_SRS_DEV_PATH, IgnitionFilesCrs } from './ignition_files_crs.js';
 import { mkdirSync, readFileSync, writeFileSync } from 'fs';
-import { readFile } from 'fs/promises';
+import { readFile, stat } from 'fs/promises';
 import createDebug from 'debug';
+import { homedir } from 'os';
 
 const debug = createDebug('bb.js:crs');
 
@@ -12,47 +13,48 @@ const debug = createDebug('bb.js:crs');
 export class Crs {
   constructor(public readonly numPoints: number, public readonly path: string) {}
 
-  static async new(numPoints: number, crsPath = './crs') {
+  static async new(numPoints: number, crsPath = homedir() + '/.bb-crs') {
     const crs = new Crs(numPoints, crsPath);
     await crs.init();
     return crs;
   }
 
   async init() {
     mkdirSync(this.path, { recursive: true });
-    const size = await readFile(this.path + '/size', 'ascii').catch(() => undefined);
-    if (size && +size >= this.numPoints) {
-      debug(`using cached crs of size: ${size}`);
+
+    const g1FileSize = await stat(this.path + '/bn254_g1.dat')
+      .then(stats => stats.size)
+      .catch(() => 0);
+    const g2FileSize = await stat(this.path + '/bn254_g2.dat')
+      .then(stats => stats.size)
+      .catch(() => 0);
+
+    if (g1FileSize >= this.numPoints * 64 && g1FileSize % 64 == 0 && g2FileSize == 128) {
+      debug(`using cached crs of size: ${g1FileSize / 64}`);
       return;
     }
 
-    const ignitionCrs = new IgnitionFilesCrs(this.numPoints);
-    const crs = ignitionCrs.pathExists() ? new IgnitionFilesCrs(this.numPoints) : new NetCrs(this.numPoints);
-    if (crs instanceof NetCrs) {
-      debug(`downloading crs of size: ${this.numPoints}`);
-    } else {
-      debug(`loading igntion file crs of size: ${this.numPoints}`);
-    }
+    debug(`downloading crs of size: ${this.numPoints}`);
+    const crs = new NetCrs(this.numPoints);
     await crs.init();
-    writeFileSync(this.path + '/size', this.numPoints.toString());
-    writeFileSync(this.path + '/g1.dat', crs.getG1Data());
-    writeFileSync(this.path + '/g2.dat', crs.getG2Data());
+    writeFileSync(this.path + '/bn254_g1.dat', crs.getG1Data());
+    writeFileSync(this.path + '/bn254_g2.dat', crs.getG2Data());
   }
 
   /**
    * G1 points data for prover key.
    * @returns The points data.
    */
   getG1Data(): Uint8Array {
-    return readFileSync(this.path + '/g1.dat');
+    return readFileSync(this.path + '/bn254_g1.dat');
   }
 
   /**
    * G2 points data for verification key.
    * @returns The points data.
    */
   getG2Data(): Uint8Array {
-    return readFileSync(this.path + '/g2.dat');
+    return readFileSync(this.path + '/bn254_g2.dat');
   }
 }