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feat: support halo2 (de)serialization of point to/from proof
Halo2 encodes point with a compression making use of a spare bit of base field. But our copyable was a just memory copy including y and infinity flag. To match with an outcome of Halo2 and furthermore support various encoding scheme, `Transcript` class delegates encoding to a child class.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| // Copyright 2020-2022 The Electric Coin Company | ||
| // Copyright 2022 The Halo2 developers | ||
| // Use of this source code is governed by a MIT/Apache-2.0 style license that | ||
| // can be found in the LICENSE-MIT.halo2 and the LICENCE-APACHE.halo2 | ||
| // file. | ||
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| #ifndef TACHYON_ZK_PLONK_HALO2_PROOF_SERIALIZER_H_ | ||
| #define TACHYON_ZK_PLONK_HALO2_PROOF_SERIALIZER_H_ | ||
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| #include <type_traits> | ||
| #include <utility> | ||
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| #include "tachyon/base/buffer/buffer.h" | ||
| #include "tachyon/math/elliptic_curves/affine_point.h" | ||
| #include "tachyon/math/finite_fields/prime_field_base.h" | ||
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| namespace tachyon::zk::halo2 { | ||
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| template <typename F, typename SFINAE = void> | ||
| class ProofSerializer; | ||
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| template <typename F> | ||
| class ProofSerializer< | ||
| F, std::enable_if_t<std::is_base_of_v<math::PrimeFieldBase<F>, F>>> { | ||
| public: | ||
| [[nodiscard]] static bool ReadFromProof(const base::Buffer& buffer, | ||
| F* value) { | ||
| return buffer.Read(value); | ||
| } | ||
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| [[nodiscard]] static bool WriteToProof(const F& value, base::Buffer& buffer) { | ||
| return buffer.Write(value); | ||
| } | ||
| }; | ||
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| template <typename Curve> | ||
| class ProofSerializer<math::AffinePoint<Curve>> { | ||
| public: | ||
| using BaseField = typename math::AffinePoint<Curve>::BaseField; | ||
| using BigIntTy = typename BaseField::BigIntTy; | ||
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| static_assert(BaseField::kModulusBits % 8 != 0, | ||
| "Halo2 needs 1 spare bit to put sign bit"); | ||
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| constexpr static size_t kByteSize = BaseField::kLimbNums * sizeof(uint64_t); | ||
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| [[nodiscard]] static bool ReadFromProof(const base::Buffer& buffer, | ||
| math::AffinePoint<Curve>* point_out) { | ||
| uint8_t bytes[kByteSize]; | ||
| if (!buffer.Read(bytes)) return false; | ||
| uint8_t is_odd = bytes[kByteSize - 1] >> 7; | ||
| bytes[kByteSize - 1] &= 0b01111111; | ||
| BaseField x = BaseField::FromBigInt(BigIntTy::FromBytesLE(bytes)); | ||
| if (x.IsZero()) { | ||
| *point_out = math::AffinePoint<Curve>::Zero(); | ||
| return true; | ||
| } else { | ||
| std::optional<math::AffinePoint<Curve>> point = | ||
| math::AffinePoint<Curve>::CreateFromX(x, is_odd); | ||
| if (!point.has_value()) return false; | ||
| *point_out = std::move(point).value(); | ||
| return true; | ||
| } | ||
| } | ||
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| [[nodiscard]] static bool WriteToProof(const math::AffinePoint<Curve>& point, | ||
| base::Buffer& buffer) { | ||
| if (point.infinity()) { | ||
| constexpr uint8_t kZeroBytes[kByteSize] = { | ||
| 0, | ||
| }; | ||
| return buffer.Write(kZeroBytes); | ||
| } else { | ||
| uint8_t is_odd = uint8_t{point.y().ToBigInt().IsOdd()} << 7; | ||
| std::array<uint8_t, kByteSize> x = point.x().ToBigInt().ToBytesLE(); | ||
| if (!buffer.Write(x)) return false; | ||
| return buffer.WriteAt(buffer.buffer_offset() - 1, | ||
| static_cast<uint8_t>(x[kByteSize - 1] | is_odd)); | ||
| } | ||
| } | ||
| }; | ||
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| } // namespace tachyon::zk::halo2 | ||
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| #endif // TACHYON_ZK_PLONK_HALO2_PROOF_SERIALIZER_H_ |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| // Copyright 2020-2022 The Electric Coin Company | ||
| // Copyright 2022 The Halo2 developers | ||
| // Use of this source code is governed by a MIT/Apache-2.0 style license that | ||
| // can be found in the LICENSE-MIT.halo2 and the LICENCE-APACHE.halo2 | ||
| // file. | ||
|
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| #include "tachyon/zk/plonk/halo2/proof_serializer.h" | ||
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| #include <vector> | ||
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| #include "gmock/gmock.h" | ||
| #include "gtest/gtest.h" | ||
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| #include "tachyon/base/buffer/vector_buffer.h" | ||
| #include "tachyon/math/elliptic_curves/bn/bn254/g1.h" | ||
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| namespace tachyon::zk::halo2 { | ||
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| namespace { | ||
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| using namespace math::bn254; | ||
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| class ProofSerializerTest : public testing::Test { | ||
| public: | ||
| static void SetUpTestSuite() { G1Curve::Init(); } | ||
| }; | ||
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| } // namespace | ||
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| TEST_F(ProofSerializerTest, SerializeScalar) { | ||
| struct { | ||
| std::string_view hex; | ||
| std::vector<uint8_t> proof; | ||
| } tests[] = { | ||
| {"0x2482c9ce1f365ed93c2afe1df9c673b0ba65278badd4d150f3b848cdd3d0cec8", | ||
| {200, 206, 208, 211, 205, 72, 184, 243, 80, 209, 212, | ||
| 173, 139, 39, 101, 186, 176, 115, 198, 249, 29, 254, | ||
| 42, 60, 217, 94, 54, 31, 206, 201, 130, 36}}, | ||
| }; | ||
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| for (const auto& test : tests) { | ||
| std::vector<uint8_t> buffer; | ||
| buffer.resize(test.proof.size()); | ||
| base::Buffer write_buf(buffer.data(), buffer.size()); | ||
| Fr expected = Fr::FromHexString(test.hex); | ||
| ASSERT_TRUE(ProofSerializer<Fr>::WriteToProof(expected, write_buf)); | ||
| EXPECT_THAT(buffer, testing::ElementsAreArray(test.proof)); | ||
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| write_buf.set_buffer_offset(0); | ||
| Fr actual; | ||
| ASSERT_TRUE(ProofSerializer<Fr>::ReadFromProof(write_buf, &actual)); | ||
| EXPECT_EQ(actual, expected); | ||
| } | ||
| } | ||
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| TEST_F(ProofSerializerTest, SerializeProof) { | ||
| struct { | ||
| std::array<std::string_view, 2> hex; | ||
| std::vector<uint8_t> proof; | ||
| } tests[] = { | ||
| // even point | ||
| {{ | ||
| "0x233bd4dc42ffd123f6d041dca2117acea5f6a201b4612a81e7081cad001df470", | ||
| "0x14ecc49a7d74ee9059862ca5237c72f22dc6c39b64ec3e7c4ec314187577ee56", | ||
| }, | ||
| {112, 244, 29, 0, 173, 28, 8, 231, 129, 42, 97, | ||
| 180, 1, 162, 246, 165, 206, 122, 17, 162, 220, 65, | ||
| 208, 246, 35, 209, 255, 66, 220, 212, 59, 35}}, | ||
| // odd point | ||
| {{ | ||
| "0x1ec72fa9df2846c267ad6bc77e438c0d8c0c9bba978be3095cc48b0334299dbb", | ||
| "0x2c1b5dfdca4dfc40a864355fead42fb3656a8a3304ad11b1dee1a4b924ac5a03", | ||
| }, | ||
| {187, 157, 41, 52, 3, 139, 196, 92, 9, 227, 139, | ||
| 151, 186, 155, 12, 140, 13, 140, 67, 126, 199, 107, | ||
| 173, 103, 194, 70, 40, 223, 169, 47, 199, 158}}, | ||
| }; | ||
|
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| for (const auto& test : tests) { | ||
| std::vector<uint8_t> buffer; | ||
| buffer.resize(test.proof.size()); | ||
| base::Buffer write_buf(buffer.data(), buffer.size()); | ||
| Fq x = Fq::FromHexString(test.hex[0]); | ||
| Fq y = Fq::FromHexString(test.hex[1]); | ||
| G1AffinePoint expected(x, y); | ||
| ASSERT_TRUE( | ||
| ProofSerializer<G1AffinePoint>::WriteToProof(expected, write_buf)); | ||
| EXPECT_THAT(buffer, testing::ElementsAreArray(test.proof)); | ||
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| write_buf.set_buffer_offset(0); | ||
| G1AffinePoint actual; | ||
| ASSERT_TRUE( | ||
| ProofSerializer<G1AffinePoint>::ReadFromProof(write_buf, &actual)); | ||
| EXPECT_EQ(actual, expected); | ||
| } | ||
| } | ||
|
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| } // namespace tachyon::zk::halo2 |
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