Authenticating messages sent between a vehicle and a central facility

1. A method of transmitting short message service (SMS) messages between a vehicle and a central facility, comprising the steps of:

(a) determining an authentication tone having a unique characteristic;

(b) generating an SMS message that includes computer-readable data representing the authentication tone;

(c) sending the SMS message to a central facility;

(d) establishing a call between the central facility and the vehicle using a vehicle telematics unit and a wireless carrier system;

(e) generating the determined authentication tone at the vehicle; and

(f) transmitting the generated authentication tone over the established call to the central facility.

2. The method of claim 1 , wherein the unique characteristic further comprises one or more of a specific frequency, a tone pulse length, a number of tone pulses, or a time delay between pulses.

3. The method of claim 2 , further comprising the step of randomly selecting the specific frequency at the vehicle.

4. The method of claim 1 , further comprising the steps of:

receiving at the central facility the transmitted authentication tone;

comparing the received authentication tone with the computer readable data; and

validating the SMS message based on the comparison.

5. The method of claim 2 , further comprising the steps of determining at the central facility the number of tone pulses the authentication tone can include; and sending a value representing the number of tone pulses to the vehicle from the central facility.

6. The method of claim 1 , wherein the authentication tone uniquely identifies the vehicle from other vehicles.

7. The method of claim 1 , wherein step (b) further comprises including the computer-readable data representing the authentication tone in the header or payload of the SMS message.

8. The method of claim 2 , wherein step (b) further comprises including a value in the computer-readable data that represents the number of tone pulses and the time delay between pulses.

9. The method of claim 1 , further comprising the step of automatically establishing the call between the central facility and the vehicle based on step (c).

10. The method of claim 1 , further comprising the step of generating the authentication tone using equipment on the vehicle that is capable of generating a dual tone multiple frequency (DTMF) tone.

11. A method of transmitting short message service (SMS) messages between a vehicle and a central facility, comprising the steps of:

(a) receiving at a central facility an SMS message that is sent from one of a plurality of vehicles and that includes computer-readable data representing an authentication tone having a unique characteristic;

(b) receiving a call from one of the vehicles at the central facility via a wireless carrier system;

(c) detecting an authentication tone that is transmitted via the received call from one of the vehicles;

(d) comparing the detected authentication tone with the computer-readable data representing the authentication tone that is included with the SMS messages; and

(e) validating the SMS message if the detected authentication tone matches the computer-readable data.

12. The method of claim 11 , wherein the unique characteristic further comprises one or more of a specific frequency, a tone pulse length, a number of tone pulses, or a time delay between pulses.

13. The method of claim 11 , wherein the SMS message further comprises computer-readable data identifying the unique characteristic as a specific frequency, a tone pulse length, a number of tone pulses, or a time delay between pulses.

14. The method of claim 11 , further comprising the steps of determining at the central facility the number of tone pulses the authentication tone can include and sending a value representing the number of tone pulses to the vehicle from the central facility.

15. The method of claim 11 , further comprising the step of including computer-readable data that represents the unique characteristic in the header or payload of the SMS message.

16. The method of claim 13 , wherein the computer-readable data includes a value representing the number of tone pulses and the time delay between pulses.

17. The method of claim 11 , further comprising the step of detecting the frequency of the authentication tone using equipment at the central facility that is also used to detect a dual tone multiple frequency (DTMF) tone.

18. A method of transmitting short message service (SMS) messages between a vehicle and a central facility, comprising the steps of:

(a) specifying at a vehicle an authentication tone having a randomly-chosen frequency, a number of tone pulses, and a time delay between each tone pulse;

(b) generating an SMS message that includes computer-readable data representing the randomly-chosen frequency, the number of tone pulses, and the time delay;

(c) sending the SMS message from the vehicle to a central facility via a wireless carrier system;

(d) establishing a call between the vehicle and the central facility via the wireless carrier system;

(e) transmitting the authentication tone from the vehicle to the central facility using the established call;

(f) detecting the frequency of the authentication tone, the number of tone pulses, and the time delay between each tone pulse received at the central facility;

(g) comparing the results of step (f) with the computer-readable data of the SMS message; and

(h) validating the SMS message if the computer-readable data matches the results of step (f).

19. The method of claim 18 , wherein the authentication tone uniquely identifies the vehicle from other vehicles.

20. The method of claim 18 , further comprising the steps of determining at the central facility the number of tone pulses and sending a value representing the number of tone pulses to the vehicle from the central facility.