A Study of Key Management and Location Management for Mobile Networks

Finally, I want to express my deepest gratitude to my wife Chikako, my daughter Tsugumi, and my son Tenga for their support and encouragemet. Abstract The subjects of this thesis are secure key management and secure location management for mobile nodes on wireless mobile networks. Recently, mobile networks become increasingly popular with the widespread availability of cellular phones and notebook PC's. Moreover new mobile networks are appearing, for example autonomous and flexible networks as typified by ad-hoc / mesh networks and ubiquitous computing / networks as typified by sensor networks and radio frequency identification (RFID) systems. On wireless mobile networks, attackers are easy to eavesdrop and connect communication channels. Therefore it is important to prevent attacks in comparison to traditional wired networks. Cryptography is an essential tool in information security. Symmetric cryptography uses the same key (symmetric key) for message encryption and message decryption. In case that a valid user Alice has a symmetric key secretly, Alice can securely share a secret message with another user Bob whom Alice selects by giving the symmetric key to Bob secretly. Also, asymmetric cryptography uses a key (public key) to encrypt a secret message and uses another key (private key) to decrypt an encrypted secret message. According to publish a public key, the corresponding private key holder can decrypt encrypted messages that other users encrypt using the public key. In general, public key infrastructure (PKI) that a trusted third party certificates an identity of a public key is used for knowing whose public key. Such techniques (symmetric key sharing and PKI) are called " key management ". Thus cryptography requires secure key management. Here, mobile networks have significant features that are different from traditional wired networks, and these features are 1) dynamic change of network topology, 2) no authorities and so on. Consequently, there are still many key management problems. On the other hand, many mobile nodes are always moving on mobile networks. Therefore it is important that network managers and service providers obtain location information of mobile nodes. As location measurement technology, there are techniques that calculate a location using a difference time between radio waves as typified by global positioning system (GPS) and techniques that confirm a location using information, which can be obtained in a specific location, as typified by RFID and beacons. Newly, location-based services (LBSs), which depend on geographical locations of mobile nodes, receive mach attention on ubiquitous …