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Unformatted text preview: Chapter 16: Authentication in Distributed System Ajay Kshemkalyani and Mukesh Singhal Distributed Computing: Principles, Algorithms, and Systems Cambridge University Press A. Kshemkalyani and M. Singhal (Distributed Computing) Authentication in Distributed System CUP 2008 1 / 54 Distributed Computing: Principles, Algorithms, and Systems Introduction A distributed system is susceptible to a variety of security threats. A principal can impersonate other principal and authentication becomes an important requirement. Authentication is a process by which one principal verifies the identity of other principal. In oneway authentication, only one principal verifies the identity of the other principal. In mutual authentication, both communicating principals verify each others identity. A. Kshemkalyani and M. Singhal (Distributed Computing) Authentication in Distributed System CUP 2008 2 / 54 Distributed Computing: Principles, Algorithms, and Systems Background and definitions Authentication is a process of verifying that the principals identity is as claimed. Authentication is based on the possession of some secret information, like password, known only to the entities participating in the authentication. When an entity wants to authenticate another entity, the former will verify if the latter possesses the knowledge of the secret. A. Kshemkalyani and M. Singhal (Distributed Computing) Authentication in Distributed System CUP 2008 3 / 54 Distributed Computing: Principles, Algorithms, and Systems A simple classification of authentication protocols Classified based on the cryptographic technique used. There are two basic types of cryptographic techniques: symmetric (private key) and asymmetric (public key). Symmetric cryptography uses a single private key to both encrypt and decrypt data. (Let { X } k denote the encryption of X using a symmetric key k and { Y } k 1 denote the decryption of Y using a symmetric key k.) Asymmetric cryptography, also called Publickey cryptography, uses a secret key (private key) that must be kept from unauthorized users and a public key that is made public. (For a principal x, K x and K 1 x denote its public and private keys, respectively.) Data encrypted with the public key can be decrypted only by the corresponding private key, and data signed with the private key can only be verified with the corresponding public key. A. Kshemkalyani and M. Singhal (Distributed Computing) Authentication in Distributed System CUP 2008 4 / 54 Distributed Computing: Principles, Algorithms, and Systems Authentication protocols with symmetric cryptosystem In a symmetric cryptosystem, authentication protocols can be designed using to the following principle: If a principal can correctly encrypt a message using a key that the verifier believes is known only to a principal with the claimed identity (outside of the verifier), this act constitutes sufficient proof of identity. A. Kshemkalyani and M. Singhal (Distributed Computing) Authentication in Distributed System CUP 2008 5 / 54 Distributed Computing: Principles, Algorithms, and Systems...
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 Spring '12
 Ajay
 Algorithms, Distributed Computing

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