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Add interface for two-party key generation protocol
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‎dpf/key_generation_protocol/BUILD‎

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# Copyright 2023 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
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load("@rules_cc//cc:defs.bzl", "cc_library")
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load("@rules_proto//proto:defs.bzl", "proto_library")
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package(
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default_visibility = ["//visibility:public"],
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)
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cc_library(
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name = "key_generation_protocol",
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srcs = ["key_generation_protocol.cc"],
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hdrs = ["key_generation_protocol.h"],
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deps = [
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":key_generation_protocol_cc_proto",
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"//dpf:distributed_point_function",
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"//dpf:distributed_point_function_cc_proto",
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"//dpf:status_macros",
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"@com_google_absl//absl/memory",
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"@com_google_absl//absl/numeric:int128",
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"@com_google_absl//absl/status",
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"@com_google_absl//absl/status:statusor",
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],
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)
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cc_test(
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name = "key_generation_protocol_test",
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srcs = ["key_generation_protocol_test.cc"],
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deps = [
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":key_generation_protocol",
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"//dpf:distributed_point_function_cc_proto",
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"//dpf/internal:status_matchers",
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"@com_github_google_googletest//:gtest_main",
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],
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)
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cc_proto_library(
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name = "key_generation_protocol_cc_proto",
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deps = [":key_generation_protocol_proto"],
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)
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proto_library(
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name = "key_generation_protocol_proto",
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srcs = ["key_generation_protocol.proto"],
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deps = ["//dpf:distributed_point_function_proto"],
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)

‎dpf/key_generation_protocol/key_generation_protocol.cc‎

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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "dpf/key_generation_protocol/key_generation_protocol.h"
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#include "absl/memory/memory.h"
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#include "absl/status/status.h"
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#include "dpf/distributed_point_function.h"
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#include "dpf/status_macros.h"
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namespace distributed_point_functions {
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KeyGenerationProtocol::KeyGenerationProtocol(
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std::unique_ptr<DistributedPointFunction> dpf, int party)
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: dpf_(std::move(dpf)), party_(party) {}
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absl::StatusOr<std::unique_ptr<KeyGenerationProtocol>>
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KeyGenerationProtocol::Create(absl::Span<const DpfParameters> parameters,
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int party) {
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if (party != 0 && party != 1) {
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return absl::InvalidArgumentError("`party` must be 0 or 1");
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}
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DPF_ASSIGN_OR_RETURN(auto dpf,
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DistributedPointFunction::CreateIncremental(parameters));
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return absl::WrapUnique(new KeyGenerationProtocol(std::move(dpf), party));
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}
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} // namespace distributed_point_functions

‎dpf/key_generation_protocol/key_generation_protocol.h‎

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/*
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* Copyright 2023 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef DISTRIBUTED_POINT_FUNCTIONS_DPF_KEY_GENERATION_PROTOCOL_KEY_GENERATION_PROTOCOL_H_
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#define DISTRIBUTED_POINT_FUNCTIONS_DPF_KEY_GENERATION_PROTOCOL_KEY_GENERATION_PROTOCOL_H_
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#include <memory>
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#include "absl/numeric/int128.h"
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#include "absl/status/statusor.h"
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#include "dpf/distributed_point_function.h"
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#include "dpf/distributed_point_function.pb.h"
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#include "dpf/key_generation_protocol/key_generation_protocol.pb.h"
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namespace distributed_point_functions {
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// A two-party protocol for generating a DPF key.
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// For each level of the DPF evaluation tree, the following messages are
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// exchanged between the parties. We refer to the corresponding lines in
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// Algorithm 8 of https://eprint.iacr.org/2022/866.pdf.
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//
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// 1. Perform two parallel OTs to obtain shares of s_{CW} (Step 5)
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// 2. Exchange shares of s_{CW}, t^L_{CW}, and t^R_{CW} (Step 5)
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// 3. Perform two parallel OTs to obtain shares of W_{CW} (Step 11)
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// 4. Exchange shares of W_{CW}.
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//
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// These steps correspond to the following functions in this class:
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//
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// 1a. ComputeSeedCorrectionOtReceiverMessage
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// 1b. ComputeSeedCorrectionOtSenderMessage
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// 2. ComputeSeedCorrectionShare
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// 3a. ComputeValueCorrectionOtReceiverMessage
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// 3b. ComputeValueCorrectionOtSenderMessage
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// 4. ComputeValueCorrectionShare
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//
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// Each of these methods takes the other party's message from the previous
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// round, as well as a ProtocolState message containing the party's local state.
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// It updates the state and returns the computed message or a Status indicating
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// any errors.
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//
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// NOTE: We may want to compute the value correction first, as done in
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// DistributedPointFunction::GenerateIncremental.
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class KeyGenerationProtocol {
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public:
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struct ProtocolState {
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int tree_level;
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// Add more local state variables here.
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};
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// Creates a new instance of the key generation protocol for a DPF with the
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// given parameters. Party must be 0 or 1.
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static absl::StatusOr<std::unique_ptr<KeyGenerationProtocol>> Create(
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absl::Span<const DpfParameters> parameters, int party);
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// Create ProtocolState given shares of alphas and betas. Arguments are given
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// as Spans to allow batching.
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absl::StatusOr<ProtocolState> Initialize(
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absl::Span<const absl::uint128> alpha_shares,
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absl::Span<const std::vector<Value>> beta_shares) const;
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// Receiver OT message for the MUX in Step 5. Just takes the state as input.
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absl::StatusOr<SeedCorrectionOtReceiverMessage>
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ComputeSeedCorrectionOtReceiverMessage(ProtocolState& state) const;
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// Computes the sender OT message given the receiver message and the state.
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absl::StatusOr<SeedCorrectionOtSenderMessage>
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ComputeSeedCorrectionOtSenderMessage(
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const SeedCorrectionOtReceiverMessage& seed_ot_receiver_message,
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ProtocolState& state) const;
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// Computes the share of the seed correction word given the sender OT message
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// and the state.
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absl::StatusOr<SeedCorrectionShare> ComputeSeedCorrectionOtShare(
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const SeedCorrectionOtSenderMessage& seed_ot_sender_message,
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ProtocolState& state) const;
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// Updates the state with the other party's seed correction share.
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absl::Status ApplySeedCorrectionShare(
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const SeedCorrectionShare& seed_correction_share,
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ProtocolState& state) const;
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// Computes the OT receiver message for the MUX gate in Step 11 given the
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// state.
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absl::StatusOr<ValueCorrectionOtReceiverMessage>
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ComputeValueCorrectionOtReceiverMessage(ProtocolState& state) const;
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// Computes the OT sender message in Step 11 given the receiver message and
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// the state.
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absl::StatusOr<ValueCorrectionOtSenderMessage>
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ComputeValueCorrectionOtSenderMessage(
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const ValueCorrectionOtReceiverMessage& value_ot_receiver_message,
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ProtocolState& state) const;
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// Computes the value correction share given the OT sender message and the
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// state.
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absl::StatusOr<ValueCorrectionShare> ComputeValueCorrectionOtShare(
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const ValueCorrectionOtSenderMessage& value_ot_sender_message,
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ProtocolState& state) const;
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// Updates the state with the other party's value correction share.
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absl::Status ApplyValueCorrectionShare(
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const ValueCorrectionShare& value_correction_share,
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ProtocolState& state) const;
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// Finalizes the protocol after all tree levels have been computed and returns
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// the generated DpfKey.
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absl::StatusOr<DpfKey> Finalize(ProtocolState& state) const;
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private:
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explicit KeyGenerationProtocol(std::unique_ptr<DistributedPointFunction> dpf,
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int party);
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std::unique_ptr<DistributedPointFunction> dpf_;
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int party_;
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};
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} // namespace distributed_point_functions
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#endif // DISTRIBUTED_POINT_FUNCTIONS_DPF_KEY_GENERATION_PROTOCOL_KEY_GENERATION_PROTOCOL_H_

‎dpf/key_generation_protocol/key_generation_protocol.proto‎

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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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syntax = "proto3";
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package distributed_point_functions;
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import "dpf/distributed_point_function.proto";
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// For faster allocations of sub-messages.
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option cc_enable_arenas = true;
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message SeedCorrectionOtSenderMessage {
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repeated Block masked_message_one = 1;
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repeated Block masked_message_two = 2;
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}
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message SeedCorrectionOtReceiverMessage {
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repeated bool choice_bit_mask = 1;
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}
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message SeedCorrectionShare {
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repeated Block seed = 1;
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repeated bool control_bit_left = 2;
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repeated bool control_bit_right = 3;
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}
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message ValueCorrectionOtSenderMessage {
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repeated Value masked_message_one = 1;
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repeated Value masked_message_two = 2;
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}
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message ValueCorrectionOtReceiverMessage {
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repeated bool choice_bit_mask = 1;
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}
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message ValueCorrectionShare {
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repeated Value value = 1;
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}

‎dpf/key_generation_protocol/key_generation_protocol_test.cc‎

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// Copyright 2023 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "dpf/key_generation_protocol/key_generation_protocol.h"
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#include "dpf/distributed_point_function.pb.h"
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#include "dpf/internal/status_matchers.h"
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#include "gmock/gmock.h"
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#include "gtest/gtest.h"
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namespace distributed_point_functions {
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namespace {
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using dpf_internal::IsOkAndHolds;
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using dpf_internal::StatusIs;
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using ::testing::HasSubstr;
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using ::testing::NotNull;
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class KeyGenerationProtocolTest : public testing::Test {
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protected:
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void SetUp() override {
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parameters_.resize(2);
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parameters_[0].set_log_domain_size(5);
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parameters_[0].mutable_value_type()->mutable_integer()->set_bitsize(64);
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parameters_[1].set_log_domain_size(10);
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parameters_[1].mutable_value_type()->mutable_integer()->set_bitsize(64);
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}
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std::vector<DpfParameters> parameters_;
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};
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TEST_F(KeyGenerationProtocolTest, CreateSucceeds) {
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constexpr int party = 0;
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EXPECT_THAT(KeyGenerationProtocol::Create(parameters_, party),
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IsOkAndHolds(NotNull()));
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}
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TEST_F(KeyGenerationProtocolTest, CreateFailsIfPartyIsNot0Or1) {
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constexpr int party = 2;
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EXPECT_THAT(KeyGenerationProtocol::Create(parameters_, party),
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StatusIs(absl::StatusCode::kInvalidArgument, HasSubstr("party")));
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}
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} // namespace
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} // namespace distributed_point_functions

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