Identifying and authenticating users based on passive factors determined from sensor data

1. A method for authenticating and/or identifying a user of an electronic device, comprising:

perform a first authentication of the user;

in response to detecting each of multiple trigger events subsequent to the first authentication:

collecting sensor data from one or more sensors in the electronic device;

extracting a feature vector from the sensor data, wherein extracting the feature vector involves using signal-processing techniques to extract multiple features from the collected sensor data; and

based on the feature vector, calculating a security score indicating a confidence that the electronic device is being used by the user and/or a probability of the electronic device being operated by someone other than the user; and

after said first authentication, when the device is operated to access a service that requires user authentication:

retrieving a most recent security score;

when the most recent security score exceeds a threshold:

suppressing a login feature of the service from being displayed to the user; and

forwarding to the service login data for the user that was obtained from a password management system; and

when the most recent security score is less than the threshold, displaying the login feature for completion.

2. The method of claim 1 , wherein:

the electronic device is a portable electronic device; and

the sensor data includes movement-related sensor data caused by movement of the portable electronic device while the portable electronic device is in control of the user.

3. The method of claim 2 , wherein:

the movement-related sensor data includes accelerometer data gathered while the user is walking; and

the accelerometer data reflects a characteristic gait of the user while walking.

4. The method of claim 1 , further comprising in response to detecting each of the multiple trigger events subsequent to the first authentication:

determining that the security score does not exceed a minimum value;

causing a challenge to be issued to the user; and

if the user successfully responds to the challenge, re-authenticating the user.

5. The method of claim 1 , wherein forwarding the login data comprises automatically communicating a username and password to the service.

6. The method of claim 1 , wherein the multiple trigger events comprise at least one of the following:

a detected activity of the user;

a state change associated with the electronic device;

a timer-based trigger; and

a broadcast trigger received by the electronic device.

7. The method of claim 1 , wherein the one or more sensors include one or more of the following:

an accelerometer;

a touchscreen;

a gyroscope;

an inertial sensor;

an ambient light sensor;

an image sensor;

a camera;

a temperature sensor;

a barometric-pressure sensor;

a cellular radio signal strength sensor;

a Bluetooth radio signal strength sensor;

a battery sensor;

a sensor in a mouse; and

a sensor in a trackpad.

8. The method of claim 1 , wherein:

the user uses one of multiple ways to accomplish a task with the service; and

the sensor data includes semantic information that comprises a particular flow through the service associated with the one way of accomplishing the task.

9. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for authenticating and/or identifying a user of an electronic device, the method comprising:

performing a first authentication of the user;

in response to detecting each of multiple trigger events subsequent to the first authentication:

collecting sensor data from one or more sensors in the electronic device;

extracting a feature vector from the sensor data, wherein extracting the feature vector involves using signal-processing techniques to extract multiple features from the collected sensor data; and

based on the feature vector, calculating a security score indicating a confidence that the electronic device is being used by the user and/or a probability of the electronic device being operated by someone other than the user; and

after said first authentication, when the device is operated to access a service that requires user authentication:

retrieving a most recent security score;

when the most recent security score exceeds a threshold:

suppressing a login feature of the service from being displayed to the user; and

forwarding to the service login data for the user that was obtained from a password management system; and

when the most recent security score is less than the threshold, displaying the login feature for completion.

10. The non-transitory computer-readable storage medium of claim 9 , wherein:

the electronic device is a portable electronic device; and

the sensor data includes movement-related sensor data caused by movement of the portable electronic device while the portable electronic device is in control of the user.

11. The non-transitory computer-readable storage medium of claim 10 , wherein:

the movement-related sensor data includes accelerometer data gathered while the user is walking; and

the accelerometer data reflects a characteristic gait of the user while walking.

12. The non-transitory computer-readable storage medium of claim 9 , further comprising in response to each of the multiple trigger events subsequent to the first authentication:

determining that the security score does not exceed a minimum value;

causing a challenge to be issued to the user; and

if the user successfully responds to the challenge, re-authenticating.

13. The non-transitory computer-readable storage medium of claim 9 , wherein forwarding the login data comprises automatically communicating a username and password to the service.

14. The non-transitory computer-readable storage medium of claim 9 , wherein the multiple trigger events comprise at least one of the following:

a detected activity of the user;

a state change associated with the electronic device;

a timer-based trigger; and

a broadcast trigger received by the electronic device.

15. The non-transitory computer-readable storage medium of claim 9 , wherein the one or more sensors include one or more of the following:

an accelerometer;

a touchscreen;

a gyroscope;

an inertial sensor;

an ambient light sensor;

an image sensor;

a camera;

an odor sensor;

a temperature sensor;

a barometric-pressure sensor;

a cellular radio signal strength sensor;

a Bluetooth radio signal strength sensor;

a near-field communication (NFC) sensor;

a network-proximity sensor;

an infrared sensor;

a magnetometer;

a battery sensor;

a force-touch measurement sensor;

a multi-touch measurement sensor;

a sensor in a mouse;

a sensor in a trackpad; and

a keyboard-timing sensor.

16. A system that authenticates and/or identifies a user of an electronic device, comprising:

at least one processor and at least one associated memory; and

an authentication mechanism that executes on the at least one processor, wherein during operation, the authentication mechanism:

performs a first authentication of the user;

in response to detecting each of multiple trigger events subsequent to the first authentication:

collects sensor data from one or more sensors in the electronic device;

extracts a feature vector from the sensor data, wherein extracting the feature vector involves using signal-processing techniques to extract multiple features from the collected sensor data; and

based on the feature vector, calculates a security score indicating a confidence that the electronic device is being used by the user and/or a probability of the electronic device being operated by someone other than the user; and

after said first authentication, when the device is operated to access a service that requires user authentication:

retrieves a most recent security score;

when the most recent security score exceeds a threshold:

suppresses a login feature of the service from being displayed to the user; and

forwards to the service login data for the user that was obtained from a password management system; and

when the most recent security score is less than the threshold, displays the login feature for completion.

17. The system of claim 16 , wherein:

the electronic device is a portable electronic device; and

the sensor data includes movement-related sensor data caused by movement of the portable electronic device while the portable electronic device is in control of the user.

18. The system of claim 16 , wherein the one or more sensors include the following:

an odor sensor;

a near-field communication (NFC) sensor;

a network-proximity sensor;

an infrared sensor;

a magnetometer;

a force-touch measurement sensor;

a multi-touch measurement sensor; and

a keyboard-timing sensor.