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231e468e19
git-subtree-dir: erigon-lib git-subtree-mainline:3c8cbda809git-subtree-split:93d9c9d9fe
53 lines
1.9 KiB
C++
53 lines
1.9 KiB
C++
#include "pedersen_hash.h"
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#include <vector>
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#include "elliptic_curve.h"
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#include "fraction_field_element.h"
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#include "elliptic_curve_constants.h"
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#include "error_handling.h"
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namespace starkware {
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namespace {
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EcPoint<FractionFieldElement<PrimeFieldElement>> EcSubsetSumHash(
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const EcPoint<FractionFieldElement<PrimeFieldElement>>& shift_point,
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gsl::span<const EcPoint<PrimeFieldElement>> points, const PrimeFieldElement& selector_value) {
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using FractionFieldElementT = FractionFieldElement<PrimeFieldElement>;
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const auto selector_value_as_big_int = selector_value.ToStandardForm();
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const std::vector<bool> selector_bits = selector_value_as_big_int.ToBoolVector();
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ASSERT(points.size() <= selector_bits.size(), "Too many points.");
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auto partial_sum = shift_point;
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for (size_t j = 0; j < points.size(); j++) {
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const auto point = points[j].template ConvertTo<FractionFieldElementT>();
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ASSERT(partial_sum.x != point.x, "Adding a point to itself or to its inverse point.");
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if (selector_bits[j]) {
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partial_sum = partial_sum + point;
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}
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}
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for (size_t j = points.size(); j < selector_bits.size(); j++) {
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ASSERT(selector_bits[j] == 0, "Given selector is too big.");
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}
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return partial_sum;
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}
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} // namespace
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PrimeFieldElement PedersenHash(const PrimeFieldElement& x, const PrimeFieldElement& y) {
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const size_t n_element_bits = 252;
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const auto& consts = GetEcConstants();
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const auto& shift_point = consts.k_points[0];
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const auto points_span = gsl::make_span(consts.k_points).subspan(2);
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auto cur_sum = shift_point.template ConvertTo<FractionFieldElement<PrimeFieldElement>>();
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cur_sum = EcSubsetSumHash(cur_sum, points_span.subspan(0, n_element_bits), x);
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cur_sum = EcSubsetSumHash(cur_sum, points_span.subspan(n_element_bits, n_element_bits), y);
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const EcPoint<PrimeFieldElement> res = cur_sum.template ConvertTo<PrimeFieldElement>();
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return res.x;
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}
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} // namespace starkware
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