86 lines
2.7 KiB
C++
86 lines
2.7 KiB
C++
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#include <array>
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#include <cstddef>
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#include <cstdint>
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#include <iostream>
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#include <vector>
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#include "dpf.hpp"
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#include "dpf/app_flow.hpp"
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#include "dpf/app_plans.hpp"
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// A (2,3) ledger, the DPF step. Three servers replicate a ledger as
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// Shamir-style (2-of-3) shares (this group's dpf3 / VDPF+ construction). Each
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// append writes one point (slot -> amount) into all three shares; any two
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// servers reconstruct a slot. A verifiable proof (verify_dpf3) rejects an
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// append that is not a single well-formed point before it is applied.
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//
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// c++ -std=c++17 -march=native -I include -I thirdparty \
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// examples/applications/ledger23.cpp
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namespace
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{
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using dpf::fp61;
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constexpr std::size_t nslots = 256; // uint8 slot domain
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fp61 open2(fp61 a, fp61 b) // any two of three shares reconstruct
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{
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return dpf::shamir3::reconstruct(dpf::shamir3::share{1, a},
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dpf::shamir3::share{2, b});
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}
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} // namespace
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int main()
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{
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std::vector<fp61> l1(nslots), l2(nslots), l3(nslots);
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// Each append is a verified (2,3) point key.
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const std::pair<std::uint8_t, std::uint64_t> entries[] = {
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{5, 100}, {40, 25}, {5, 7}};
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for (auto [slot, amount] : entries)
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{
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auto [k1, k2, k3] = dpf::make_dpf3(slot, fp61{amount}, dpf::verifiable{});
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if (!dpf::verify_dpf3(dpf::prove_dpf3(k1, slot),
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dpf::prove_dpf3(k2, slot), dpf::prove_dpf3(k3, slot)))
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{
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std::cerr << "ledger append audit\n";
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return 1;
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}
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// Fold the (2,3) expansion into each party's ledger shares.
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dpf::eval_full_add_into(l1, k1);
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dpf::eval_full_add_into(l2, k2);
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dpf::eval_full_add_into(l3, k3);
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}
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// Slot 5 got two credits (100 + 7); slot 40 got 25; the rest are 0.
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if (open2(l1[5], l2[5]) != fp61{107}
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|| open2(l1[40], l2[40]) != fp61{25}
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|| open2(l1[0], l2[0]).raw() != 0)
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{
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std::cerr << "ledger balance\n";
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return 1;
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}
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// A proof that does not come from the same append is rejected: mixing one
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// party's token from an independent key triple fails verification.
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auto [b1, b2, b3] = dpf::make_dpf3(std::uint8_t{9}, fp61{1}, dpf::verifiable{});
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auto [c1, c2, c3] = dpf::make_dpf3(std::uint8_t{9}, fp61{1}, dpf::verifiable{});
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if (dpf::verify_dpf3(dpf::prove_dpf3(b1, std::uint8_t{9}),
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dpf::prove_dpf3(b2, std::uint8_t{9}),
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dpf::prove_dpf3(c3, std::uint8_t{9})))
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{
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std::cerr << "ledger accepted a bad append\n";
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return 1;
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}
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{
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if (int rc = dpf::app::run_measured("ledger23",
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dpf::protocol::ledger23_append_plan(0), 2))
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return rc;
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}
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std::cout << open2(l1[5], l2[5]).raw() << "\n";
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return 0;
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}
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