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- // Copyright 2020 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.
- #ifndef SERVICES_DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_H_
- #define SERVICES_DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_H_
- #include "services/device/public/cpp/generic_sensor/sensor_reading.h"
- namespace device {
- // Sensors are accurate enough that it is possible to sample sensor data to
- // implement a "fingerprint attack" to reveal the sensor calibration data.
- // This data is effectively a unique number, or fingerprint, for a device. To
- // combat this, sensor values are rounded to the nearest multiple of some small
- // number. This is still accurate enough to satisfy the needs of the sensor
- // user, but guards against this attack.
- //
- // Additional info can be found at https://crbug.com/1018180.
- //
- // Rounding also protects against using the gyroscope as a primitive microphone
- // to record audio. Additional info at https://crbug.com/1031190.
- // Units are SI meters per second squared (m/s^2).
- constexpr double kAccelerometerRoundingMultiple = 0.1;
- // Units are luxes (lx).
- constexpr int kAlsRoundingMultiple = 50;
- // Units are radians/second. This value corresponds to 0.1 deg./sec.
- constexpr double kGyroscopeRoundingMultiple = 0.00174532925199432963;
- // Units are degrees.
- constexpr double kOrientationEulerRoundingMultiple = 0.1;
- // Units are radians. This value corresponds to 0.1 degrees.
- constexpr double kOrientationQuaternionRoundingMultiple = 0.0017453292519943296;
- // Some sensor types also ignore value changes below a certain threshold to
- // avoid exposing whether a value is too close to the limit between one
- // rounded value and the next.
- constexpr int kAlsSignificanceThreshold = kAlsRoundingMultiple / 2;
- // Round |value| to be a multiple of |multiple|.
- //
- // NOTE: Exposed for testing. Please use other Rounding functions below.
- //
- // Some examples:
- //
- // ( 1.24, 0.1) => 1.2
- // ( 1.25, 0.1) => 1.3
- // (-1.24, 0.1) => -1.2
- // (-1.25, 0.1) => -1.3
- double RoundToMultiple(double value, double multiple);
- // Round accelerometer sensor reading to guard user privacy.
- void RoundAccelerometerReading(SensorReadingXYZ* reading);
- // Round gyroscope sensor reading to guard user privacy.
- void RoundGyroscopeReading(SensorReadingXYZ* reading);
- // Round ambient light sensor reading to guard user privacy.
- void RoundIlluminanceReading(SensorReadingSingle* reading);
- // Round orientation Euler angle sensor reading to guard user privacy.
- void RoundOrientationEulerReading(SensorReadingXYZ* reading);
- // Round orientation quaternion sensor reading to guard user privacy.
- // |reading| is assumed to be unscaled (unit length).
- void RoundOrientationQuaternionReading(SensorReadingQuat* reading);
- // Round the sensor reading to guard user privacy.
- void RoundSensorReading(SensorReading* reading, mojom::SensorType sensor_type);
- } // namespace device
- #endif // SERVICES_DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_UTIL_H_
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