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// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <string>
#include <vector>
#include "base/macros.h"
#include "base/time/clock.h"
#include "components/cryptauth/data_with_timestamp.h"
#include "components/cryptauth/remote_device_ref.h"
namespace cryptauth {
class BeaconSeed;
class RawEidGenerator;
// Generates ephemeral ID (EID) values that are broadcast for background BLE
// advertisements in the ProximityAuth protocol.
// Background BLE advertisements, because they're generally being advertised for
// extended periods of time, use a frequently rotating EID rotation scheme, for
// privacy reasons (EIDs should rotate more frequently to prevent others from
// tracking this device or user).
// When advertising in background mode, we offload advertising to the hardware
// in order to conserve battery. We assume, however, that the scanning side is
// not bound by battery constraints.
// For the inverse of this model, in which advertising is neither privacy- nor
// battery-sensitive, see ForegroundEidGenerator.
class BackgroundEidGenerator {
virtual ~BackgroundEidGenerator();
// Returns a list of the nearest EIDs from the current time. Note that the
// list of EIDs is sorted from earliest timestamp to latest.
virtual std::vector<DataWithTimestamp> GenerateNearestEids(
const std::vector<BeaconSeed>& beacon_seed) const;
// Given an incoming background advertisement with
// |advertisement_service_data|, identifies which device (if any) sent the
// advertisement. Returns a device ID which identifies the device. If no
// device can be identified, returns an empty string.
virtual std::string IdentifyRemoteDeviceByAdvertisement(
const std::string& advertisement_service_data,
const RemoteDeviceRefList& remote_devices) const;
friend class CryptAuthBackgroundEidGeneratorTest;
BackgroundEidGenerator(std::unique_ptr<RawEidGenerator> raw_eid_generator,
base::Clock* clock);
// Helper function to generate the EID for any |timestamp_ms|, properly
// calculating the start of the period. Returns nullptr if |timestamp_ms| is
// outside the range of |beacon_seeds|.
std::unique_ptr<DataWithTimestamp> GenerateEid(
int64_t timestamp_ms,
const std::vector<BeaconSeed>& beacon_seeds) const;
std::unique_ptr<RawEidGenerator> raw_eid_generator_;
base::Clock* clock_;
} // cryptauth