A scheme is proposed in this chapter to apply a secure digital signature scheme in a mobile-IP environment and treats the three entities in a dynamic path as either foreign agents (FA), home agents (HA) or mobile agents (MA), such that a coalition is formed containing each of the individual agents. Each agent has a pair of keys: one private and one public. The private key is evolving with time, and the public key is signed by a certification authority (CA). All the private keys of the three agents in the coalition are needed to sign a signature. Furthermore, all the messages are signed and verified. The signature is verified against a public key, computed as the product of the public keys of all three agents, and readily generated when a new dynamic path is formed. In addition, the key-evolving scheme prevents an adversary from forging past signatures under any circumstances. As a result of the schemes’ proactive refresh capability, an adversary must simultaneously compromise each MA, FA and HA in order to forge future signatures. When a new dynamic path is formed or private keys evolve to new states, an interactive, proactive synchronization scheme is employed among the agents. Thus, the loss of a mobile device, or its information, will cause minimal information damage.
