Method and apparatus for alerting nodes of a malicious node in a mobile ad-hoc communication system

1. A method for a first node to alert other nodes of a malicious node in a communication system, the method comprising:

receiving, by the first node, a message indicating that a second node is the malicious node;

determining, by the first node, a quantity of nodes identifying the second node as the malicious node;

comparing, by the first node, the quantity of nodes identifying the second node as malicious to a predetermined quorum threshold;

identifying, by the first node, the second node as malicious when the quantity of nodes identifying the second node as malicious is greater than the predetermined quorum threshold;

re-transmitting, by the first node, the message to other nodes within a predetermined hop-count from the first node indicating that the second node is the malicious node;

moving, by the first node, to a new location; and

transmitting, by the first node, a mobile alert message upon moving to a new location, with a signature of the first node appended to it, to immediate neighboring nodes indicating that the first node has determined that the quantity of nodes identifying the second node as malicious is greater than the predetermined quorum threshold.

2. The method of claim 1 wherein the determination of the quantity of nodes identifying the second node as malicious is based on a number of distinct signatures contained in message.

3. The method of claim 1 further comprising:

determining, by the first node, upon receiving the message, if a time-to-live (TTL) for the message is greater than a TTL threshold;

re-transmitting, by the first node, the message if the TTL is greater than the TTL threshold.

4. The method of claim 3 further comprising:

appending, by the first node, in the message a signature of the first node before re-transmitting the message if the message contains a number of signatures of other nodes less than the predetermined quorum threshold and the first node has identified the second node as malicious.

5. The method of claim 1 wherein the new location is beyond the predetermined hop-count from a last location of the first node.

6. The method of claim 1 wherein the operations of claim 1 are repeated periodically up to a predetermined number of times.

7. The method of claim 1 further comprising:

maintaining, by the first node, in a cache of all identified malicious nodes; and

periodically sending, by the first node, a blacklist containing the list to immediate neighboring nodes.

8. The method of claim 7 further comprising:

updating, by the first node, the cache upon receiving a blacklist containing a list of malicious nodes from a neighboring node.

9. A method for a first node to alert other nodes in a mobile ad-hoc communication system of an attack by a second node, the method comprising:

detecting, by the first node, a malicious activity by the second node;

identifying, by the first node, the second node as malicious;

transmitting, by the first node, a first alert message, with a signature of the first node appended to it, to other nodes within a predetermined hop-count from the first node indicating detection of the presence of the malicious node;

moving, by the first node, to a new location; and

transmitting, by the first node, a second alert message upon moving to the new location, with a signature of the first node appended to it, to immediate neighboring nodes indicating the presence of the malicious node, wherein the operation of moving to the new location and transmitting the second alert message are repeated periodically up to a predetermined number of times.

10. The method of claim 9 wherein the new location is beyond the predetermined hop-count from the original location of the first node.

11. The method of claim 9 further comprising:

maintaining, by the first node, in a cache of all identified malicious nodes; and

periodically sending, by the first node, a blacklist message containing the identified malicious nodes to immediate neighboring nodes.

12. The method of claim 11 further comprising:

updating, by the first node, the cache upon receiving a blacklist message containing a list of malicious nodes from a neighboring node.

13. A node comprising:

a receiver receiving a message indicating that a second node is a malicious node;

logic circuitry determining a quantity of nodes identifying the second node as the malicious node and comparing the quantity of nodes identifying the second node as malicious to a predetermined quorum threshold, and identifying the second node as malicious when the quantity of nodes identifying the second node as malicious is greater than the predetermined quorum threshold; and

a transmitter re-transmitting the message to other nodes within a predetermined hop-count from the node indicating that the second node is the malicious node and transmitting a mobile alert message, with a signature of the node appended to it, to immediate neighboring nodes indicating that the node has determined that the quantity of nodes identifying the second node as malicious is greater than the predetermined quorum threshold upon the node moving to a new location.

14. The node of claim 13 wherein the determination of the quantity of nodes identifying the second node as malicious is based on a number of distinct signatures contained in the message.

15. The node of claim 13 wherein the logic circuitry additionally determines if a time-to-live (TTL) for the message is greater than a TTL threshold, and instructs the transmitter to re-transmit the message if the TTL is greater than the TTL threshold.

16. The node of claim 15 wherein a signature of the node is appended to the message before re-transmitting the message if the message contains a number of signatures of other nodes less than the quorum threshold and the node has identified the second node as malicious.

17. The node of claim 13 wherein the new location is beyond the predetermined hop-count from the original location of the node.