Tham khảo tài liệu 'the_handbook_of_ad_hoc_wireless_networks_12', công nghệ thông tin, quản trị mạng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Simpo PDF Merge and Split Unregistered Version - http entities and grant access to guarded information to those who exhibit their knowledge of the keys 12 . Therefore it is imperative that keys be securely generated and distributed to appropriate entities. Secret keys are shared between communicating entities. A secret key can be generated by one party and distributed to another entity either through direct physical contact or a secure channel. The key can also be negotiated among entities in which case key generation and distribution are accomplished simultaneously. In public-key cryptography a public key is made public while the corresponding private key is kept secret. A public-key certificate certifies the binding between a public key and an entity. Certificates are signed bindings by a trusted party whose public key is known beforehand. Public-key certificates can be generated and distributed through a central server similar to publishing phone numbers in a phone book or a network of nodes that provides such services similar to distributing cell phone numbers by the word of mouth or a combination of the two. Public-key cryptography is often used to distribute secret keys. Security Issues in Ad Hoc Networks Security requirements in AHNs do not differ dramatically from their wired network counterparts 24 . Traditional security mechanisms still play a role in achieving AHN security. However the context to achieve security goals is different. Changes in network topology and membership occur rapidly in this new context 15 . Consequently some issues that are only of concern to high-assurance applications in wired networks are now essential to general AHN applications. In wired networks we assume the following are in place 1. Availability of routing service which implies knowledge of network topology and membership 2. Availability of supporting services such as naming and key distribution through central static system control 3. Security policy
