85 lines
2.5 KiB
C++
85 lines
2.5 KiB
C++
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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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// Express, the mailbox write (Eskandarian, Corrigan-Gibbs, Zaharia, Boneh,
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// USENIX Security 2021 §3.1). Two servers hold XOR shares of every mailbox
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// row. The client sends one `blob` DPF key each. Each server adds its
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// expansion into its share and folds the one-hot audit in the same walk.
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//
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// c++ -std=c++17 -march=native -I include -I thirdparty \
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// examples/applications/express.cpp
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namespace
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{
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constexpr std::size_t nboxes = 256;
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constexpr std::size_t row_bytes = 100;
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using row_t = dpf::blob<row_bytes>;
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} // namespace
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int main()
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{
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constexpr std::uint8_t address = 9;
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row_t message{};
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for (std::size_t i = 0; i < row_bytes; ++i)
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message.bytes[i] = static_cast<unsigned char>(i + 1);
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auto [k0, k1] = dpf::make_dpf(address, message);
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std::vector<row_t> box0(nboxes), box1(nboxes);
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// One-pass caller fold: count how many non-zero shares each server sees.
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std::size_t hot0 = 0, hot1 = 0;
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dpf::eval_full_add_into(box0, k0, [&](std::size_t, const row_t & s) {
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if (s != row_t{})
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++hot0;
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});
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dpf::eval_full_add_into(box1, k1, [&](std::size_t, const row_t & s) {
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if (s != row_t{})
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++hot1;
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});
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(void)hot0;
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(void)hot1;
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if ((box0[address] ^ box1[address]) != message)
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{
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std::cerr << "express mailbox\n";
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return 1;
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}
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if ((box0[0] ^ box1[0]) != row_t{})
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{
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std::cerr << "express neighbor\n";
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return 1;
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}
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// fp61 one-hot audit on a parallel extractable key (same walk shape).
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auto [a0, a1] = dpf::make_dpf(address, dpf::fp61{1}, dpf::extractable{});
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std::vector<dpf::fp61> challenge(nboxes);
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for (std::size_t i = 0; i < nboxes; ++i)
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challenge[i] = dpf::fp61{static_cast<std::uint64_t>(i + 1)};
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std::vector<dpf::fp61> audit0(nboxes), audit1(nboxes);
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dpf::sketch_share s0{}, s1{};
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dpf::eval_full_add_into(audit0, a0, dpf::sketch(s0, challenge));
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dpf::eval_full_add_into(audit1, a1, dpf::sketch(s1, challenge));
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if (!dpf::sketch_verify(s0, s1))
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{
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std::cerr << "express audit\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("express",
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dpf::protocol::mailbox_write_fused_plan(0, 8), 8))
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return rc;
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}
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std::cout << static_cast<unsigned>(message.bytes[0]) << "\n";
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return 0;
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}
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