78 lines
2.5 KiB
C++
78 lines
2.5 KiB
C++
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/// @file dpf/bit_inject.hpp
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/// @brief Boolean bit × arithmetic value (2PC bit_mul and 3PC RSS injection).
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#ifndef LIBDPF_INCLUDE_DPF_BIT_INJECT_HPP__
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#define LIBDPF_INCLUDE_DPF_BIT_INJECT_HPP__
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#include <cstddef>
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#include <cstdint>
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#include <utility>
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#include "hedley/hedley.h"
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#include "dpf/beaver.hpp"
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#include "dpf/rss_seed.hpp"
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#include "dpf/secret_share.hpp"
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namespace dpf
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{
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namespace bit_inject
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{
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/// @brief 2PC: `b * x` via a beaver bit_mul on an existing session.
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template <typename Ring>
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HEDLEY_WARN_UNUSED_RESULT
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beavers::wire<Ring> inject2(beavers::session<Ring> & s,
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beavers::wire<Ring> bit_wire, beavers::wire<Ring> arith_wire)
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{
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return s.bit_mul(bit_wire, arith_wire);
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}
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/// @brief Local y-factor of RSS bit injection before ring send.
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/// @details Party holds RSS bit `(b_own, b_next)` and arithmetic `(x_own, x_next)`.
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/// Local contribution mirrors RSS mul with the bit as a 0/1 factor.
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template <typename T>
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HEDLEY_WARN_UNUSED_RESULT
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T rss_inject_local(const rss::party_seeds & seeds, T b_own, T b_next,
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T x_own, T x_next, std::uint64_t index)
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{
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// Treat bit components as ring elements in {0,1}.
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return rss::rss_mul_local(seeds, b_own, b_next, x_own, x_next, index);
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}
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/// @brief After ring refresh: party receives `y_prev` and forms RSS `(y_own, y_prev)`
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/// wait — standard RSS refresh: send y_own to next, receive from prev,
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/// store `(y_own, y_from_prev)`? Actually ABY3: party i holds y_i after
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/// local mul; sends y_i to party i-1; ends with (y_i, y_{i+1}).
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template <typename T>
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HEDLEY_WARN_UNUSED_RESULT
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std::pair<T, T> rss_refresh(T y_own, T y_from_next)
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{
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return {y_own, y_from_next};
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}
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/// @brief Cleartext identity: `(b0⊕b1) * (x0+x1)`.
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template <typename Ring>
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HEDLEY_WARN_UNUSED_RESULT
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Ring inject_clear(std::uint8_t b0, std::uint8_t b1, Ring x0, Ring x1)
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{
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const Ring b = static_cast<Ring>((b0 ^ b1) & 1u);
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return static_cast<Ring>(b * (x0 + x1));
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}
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/// @brief Boolean RSS AND local factor (GF(2)).
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inline std::uint8_t rss_and_local(const rss::party_seeds & seeds,
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std::uint8_t a_own, std::uint8_t a_next, std::uint8_t b_own,
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std::uint8_t b_next, std::uint64_t index)
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{
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const std::uint8_t cross = static_cast<std::uint8_t>(
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(a_own & b_own) ^ (a_own & b_next) ^ (a_next & b_own));
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const std::uint8_t mask = static_cast<std::uint8_t>(
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rss::zero_share<std::uint8_t>(seeds, index) & 1u);
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return static_cast<std::uint8_t>(cross ^ mask);
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}
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} // namespace bit_inject
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} // namespace dpf
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#endif // LIBDPF_INCLUDE_DPF_BIT_INJECT_HPP__
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