Method for validating messages
There is provided a method for secure communications. The method includes a computing device receiving a notification comprising a message, a counter value, a signature signed by a signer and based on the message and the counter value, and an indication of the signer. The device obtains a current counter value based on an identity of the signer, checks the signature and compares the counter value with the current counter value; and, if the counter comparison and the signature checking is successful, accepting the message.
1. A method of accepting, at a communication device, a notification broadcast by a source server, the method comprising:
receiving, at the communication device, the notification, the notification containing a message, a counter value, a signature, and an indication of a signer;
processing, by the communication device, the indication to obtain a signer identity corresponding to the signer;
determining by the communication device, based on the signer identity, that there is no current counter value associated with the signer stored on the communication device;
in response to determining that there is no current counter value associated with the signer stored on the communication device, initializing, by the communication device, a new stored current counter value for the signer; and
using the new stored current counter value in determining whether to accept subsequently received notifications.
2. The method of claim 1 , wherein the new stored current counter value for the signer is initialized to zero.
3. The method of claim 2 , wherein the new stored current counter value is replaced with the counter value associated with the notification.
4. The method of claim 1 , further comprising:
receiving, at the communication device, a further notification, the further notification containing a second message, a second counter value, a second signature, and a second indication of the signer;
processing, by the communication device, the second indication to obtain the signer identity corresponding to the signer;
obtaining by the communication device, based on the signer identity, a previously stored current counter value associated with the signer;
comparing, by the communication device, the second counter value with the current counter value; and
accepting, by the communication device, the received further notification based upon the comparison.
5. The method of claim 1 , wherein the counter value comprises a certificate counter value, and wherein the indication comprises the certificate counter value and a certificate authority identity corresponding to the certificate authority that generated the certificate counter value, and wherein the method further comprises:
processing, by the communication device, the indication to obtain the certificate authority identity; and
initializing, by the communication device, a new stored current counter value for the signer or the certificate authority in response to determining that there is no stored current counter value associated with the signer or the certificate authority, respectively.
6. The method of claim 4 , wherein the counter value comprises a message counter value and the current counter value comprises a current message counter value, and wherein the indication further comprises an indication counter value and a certificate authority identity,
wherein the obtaining further comprises obtaining by the communication device, based on the signer identity and the certificate authority identity, a previously stored current indication counter value associated with the signer identity and the certificate authority identity; and
wherein the comparing further comprises comparing the indication counter value with the current indication counter value.
7. The method of claim 6 , wherein the comparing comprises confirming that the message counter is greater than the current message counter, and confirming that the indication counter is greater than or equal to the current indication counter.
8. The method of claim 1 wherein the counter value comprises a message counter value.
9. The method of claim 4 , wherein processing the indication to obtain a signer identity comprises processing the indication to obtain public key information associated with the signer, and wherein the obtaining, based on the signer identity, comprises obtaining based on the public key information.
10. The method of claim 4 , further comprising, when the notification is accepted:
processing, by the communication device, the indication to obtain public key information; and
verifying, by the communication device, the signature using the public key information to authenticate the notification.
11. The method of claim 4 , further comprising discarding the notification if the received notification is not accepted.
12. The method of claim 1 wherein the indication comprises a certificate or an implicit certificate.
13. The method of claim 4 , wherein comparing the counter value and the current counter values comprises verifying that the counter value is equal to or greater than the current counter value.
14. The method of claim 13 , further comprising if the comparison fails, discarding the notification.
15. The method of claim 4 , wherein when the received notification is accepted based upon the comparison, the method further comprising replacing the current counter value with the received counter value.
16. The method of claim 4 , wherein after the received notification is accepted, the method further comprising: communicating the message to a user.
17. The method of claim 4 , further comprising if the comparison fails, communicating the message to a user, and including a flag identifying the comparison failure.
18. The method of claim 4 , further comprising communicating the message to a user with a differential flag identifying a state of the counter value as determined by the comparison.
19. A computing device, comprising:
a memory; and
a processor coupled to the memory, the processor being configured to:
receive a notification, the notification containing a message, a counter value, a signature, and an indication of a signer;
process the indication to obtain a signer identity corresponding to the signer;
determine, based on the signer identity, that there is no current counter value associated with the signer stored on the communication device;
in response to determining that there is no current counter value associated with the signer stored on the communication device, initialize a new stored current counter value for the signer; and
use the new stored current counter value in determining whether to accept subsequently received notifications.
20. A non-transitory machine readable medium comprising instructions that when executed on a processor of a computing device enable the computing device to:
receive the notification, the notification containing a message, a counter value, a signature, and an indication of a signer;
process the indication to obtain a signer identity corresponding to the signer;
determine, based on the signer identity, that there is no current counter value associated with the signer stored on the communication device;
in response to determining that there is no current counter value associated with the signer stored on the communication device, initialize a new stored current counter value for the signer; and
use the new stored current counter value in determining whether to accept subsequently received notifications.