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applied cryptography - protocols, algorithms, and source code in c

Ea is alices public key 5 bob uses ea to decrypt dam

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Unformatted text preview: stribution system designed by IBM. It is a secret-key protocol and uses either DES in CBC mode (see Section 9.3) or a modified version of MD5 (see Section 18.5). KryptoKnight supports four security services: — User authentication (called single sign-on) — Two-party authentication — Key distribution — Authentication of data origin and content From a user’s perspective, KryptoKnight is similar to Kerberos. Some differences are: — KryptoKnight uses a hash function for authentication and encrypting tickets. — KryptoKnight does not rely on synchronized clocks; it uses nonces for challenges (see Section 3.3). — If Alice wishes to communicate with Bob, KryptoKnight has the option of allowing Alice to send a message to Bob and then for Bob to initiate the key exchange protocol. KryptoKnight has tickets and authenticators, just like Kerberos. It has TGSs, but KryptoKnight calls them authentication servers. KryptoKnight’s designers spent considerable effort minimizing the number of messages, lengths of messages, and amount of encryption. For further information on KryptoKnight, read [1110, 173, 174, 175]. 24.7 SESAME SESAME stands for Secure European System for Applications in a Multivendor Environment. It’s a European Community security project, 50 percent funded by RACE (see Section 25.7), whose primary objective is producing technology for user authentication with distributed access control. Think of it as kind of a European version of Kerberos. It’s a two-part project: Stage one is a basic prototype of the architecture, and stage two is a set of commercial projects. The three companies with the greatest hand in development are ICL in the United Kingdom, Siemens in Germany, and Bull in France. SESAME is an authentication and key-exchange system [361, 1248, 797, 1043]. It uses the Needham-Schroeder protocol, with public-key cryptography to communicate between different security domains. The system is seriously flawed in several respects. Instead of using a real encryption algorithm, they use XOR with a 64-bit key size. Even worse, they use XOR in CBC mode, which leaves half the plaintext unencrypted. In their...
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