These authentication systems can also provide, when required, confidentiality (using encryption) when transferring data over insecure networks. 4. Cryptography Cryptographic mechanisms are widely used for authentication in today's networks. There are two basic types of cryptography (symmetrical and asymmetrical). One of the fundamental problems for cryptography is to transport secret keys.
4.1. Symmetric Cryptography Symmetric Cryptography includes all systems that use the same key for encryption and decryption. So Thus, if someone gets a key, he can decrypt and read the information encrypted with it. Such a person will be able to encrypt and send any data, passing them off as the information sent to a legal owner of the secret key. This means that the knowledge of key undesirable third party fully compromises the confidentiality of the system.
Consequently, the used keys should be delivered safely, either by courier, or using a special transfer protocol keys, the best of which is the algorithm of Needham-Schroeder NS78, NS87. Widely used algorithm is des (Data Encryption Standard), which has been standardized for the protection of government information in usa. He is one of the best symmetric encryption algorithms NBS77. Well-known system, operating on open networks, is the authentication system is Kerberos (TM), which was developed as part of Project Athena at mit SNS88, BM91, KN93. Kerberos is based on the des algorithm and uses a special server that stores the secret keys of all users and services. It can generate codes that allow users and processes to identify themselves other systems.