1. A method at a computing device within an Intelligent Transportation System,
the method comprising:
determining, at the computing device, whether a short-term certificate is available to sign a message;
if the short-term certificate is available, signing the message with a private key associated with the short-term certificate;
if the short-term certificate is not available, signing the message with a private key associated with a long-term certificate; and
sending the message to a recipient.
2. The method of claim 1, wherein the short-term certificate or the long-term certificate is sent with the message.
3. The method of claim 1, wherein the short-term certificate is available if a short-term certificate with a validity period that has not expired is stored at the computing device.
4. The method of claim 1, further comprising determining that a network connection is available, and obtaining a short-term certificate.
5. The method of claim 1, wherein the short-term certificate has a cracaid set to all zeros to provide an indication that a certificate used for signing is a short-term certificate.
6. The method of claim 1, wherein the short-term certificate has a linkage value with a defined value to provide an indication that a certificate used for signing is a short-term certificate.

7. The method of claim 1, wherein the short-term certificate has a HashID with a defined value to provide an indication that a certificate used for signing is a short-term certificate.
8. The method of claim 1, wherein the short-term certificate is from an issuing certificate authority that only issues short-term certificates.
9. A computing device within an Intelligent Transportation System, the computing device comprising:
a processor; and
a communications subsystem, wherein the computing device is configured to:
determine whether a short-term certificate is available to sign a message;
if the short-term certificate is available, signing the message with a private key associated with the short-term certificate;
if the short-term certificate is not available, signing the message with a private key associated with a long-term certificate; and
sending the message to a recipient.
10. The computing device of claim 9, wherein the short-term certificate or the long-term certificate is sent with the message.
11. The computing device of claim 9, wherein the short-term certificate is available if a short-term certificate with a validity period that has not expired is stored at the computing device.
12. The computing device of claim 9, wherein the computing device is further configured to determine that a network connection is available, and obtain a short-term certificate.

13. The computing device of claim 9, wherein the short-term certificate has a cracaid set to all zeros to provide an indication that a certificate used for signing is a short-term certificate.
14. The computing device of claim 9, wherein the short-term certificate has a linkage value with a defined value to provide an indication that a certificate used for signing is a short-term certificate.
15. The computing device of claim 9, wherein the short-term certificate has a HashID with a defined value to provide an indication that a certificate used for signing is a short-term certificate.
16. The computing device of claim 9, wherein the short-term certificate is from an issuing certificate authority that only issues short-term certificates.
17. A computer readable medium for storing instruction code, which, when executed by a processor of a computing device within an Intelligent Transportation System cause the computing device to:
determine whether a short-term certificate is available to sign a message;
if the short-term certificate is available, signing the message with a private key associated with the short-term certificate;
if the short-term certificate is not available, signing the message with a private key associated with a long-term certificate; and
sending the message to a recipient.