44 lines
1.6 KiB
C++
44 lines
1.6 KiB
C++
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#include <array>
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#include <cstdint>
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#include <iostream>
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#include <tuple>
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#include <type_traits>
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#include "dpf.hpp"
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// (K,N) Shamir. The secret is the constant term of a degree K-1 polynomial.
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// Party i holds that polynomial at x = i+1. Any K shares open it. (2,3) is
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// shamir_share: make_shamir_shares(secret, slope) is deal<T, 2, 3>.
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// fp61 and gf2n both open. For gf2n, N must be less than 2^k.
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//
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// c++ -std=c++17 -march=native -I include -I thirdparty examples/mwe/shamir.cpp
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int main()
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{
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using F = dpf::fp61;
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const F secret{10};
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// p(x) = 10 + 2x + 3x^2. Parties 0, 2, and 4 are enough.
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const std::array<F, 2> coeff{{F{2}, F{3}}};
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auto shares = dpf::make_shamir_shares<3, 5>(secret, coeff);
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const F opened = dpf::shamir::reconstruct(
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std::get<0>(shares), std::get<2>(shares), std::get<4>(shares));
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const F slope{3};
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auto [s0, s1, s2] = dpf::make_shamir_shares(secret, slope);
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static_assert(std::is_same_v<decltype(s0), dpf::shamir::share<F, 0, 2, 3>>);
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const F opened23 = dpf::reconstruct(s1, s2);
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const bool on_line = s0.raw() == secret + slope * F{1}
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&& s2.raw() == secret + slope * F{3};
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using G = dpf::gf28;
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auto [g0, g1, g2] = dpf::make_shamir_shares(G{0x1b}, G{0x5a});
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const G gopen = dpf::reconstruct(g0, g2);
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const G gopen13 = dpf::reconstruct(g1, g2);
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std::cout << opened.raw() << " " << opened23.raw() << " "
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<< static_cast<unsigned>(gopen.raw()) << "\n";
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return (opened == secret && opened23 == secret && on_line
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&& gopen == G{0x1b} && gopen13 == G{0x1b})
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? 0 : 1;
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}
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