Computer and Network Security by Avi Kak Lecture SIMPLE HASH FUNCTIONS. • Practically all algorithms for computing the hashcode of a mes- sage view the messageas a sequence of n-bit blocks. The message is processed one block at a time in an iterative fashion in . Simple hash function. • Simple hash function does not satisfy the weak (and strong) collision property ; • for any message M it is very easy to generate a message M 1 such that h(M) = h(M 1): • Take arbitrary message M 2, compute h(M 2) = h 2, then • Add additional block to M 2, such that for the resulting M 3. Message Authentication Code (MAC) The process of using MAC for authentication is depicted in the following illustration − Let us now try to understand the entire process in detail − The sender uses some publicly known MAC algorithm, inputs the message and the secret key K and produces a MAC value. Similar to hash.

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# message authentication and hash functions pdf

Simple hash function. • Simple hash function does not satisfy the weak (and strong) collision property ; • for any message M it is very easy to generate a message M 1 such that h(M) = h(M 1): • Take arbitrary message M 2, compute h(M 2) = h 2, then • Add additional block to M 2, such that for the resulting M 3. Message Authentication Message authentication is concerned with: protecting the integrity of a message validating identity of originator Authenticator and Authentication Protocol Producing authenticator (three alternative functions) message encryption message authentication code (MAC) hash function. June Abstract The use of cryptographic hash functions like MD5 or SHA for message authentication has become a standard approach in many Internet applications and protocols. Though very easy to implement, these mechanisms are usually based on ad hoc techniques that lack a sound security analysis. Message Authentication Code (MAC) The process of using MAC for authentication is depicted in the following illustration − Let us now try to understand the entire process in detail − The sender uses some publicly known MAC algorithm, inputs the message and the secret key K and produces a MAC value. Similar to hash. Computer and Network Security by Avi Kak Lecture SIMPLE HASH FUNCTIONS. • Practically all algorithms for computing the hashcode of a mes- sage view the messageas a sequence of n-bit blocks. The message is processed one block at a time in an iterative fashion in . Hash Functions and Message Authentication Codes (MAC) Professor: Marius Zimand Recall that the most important services of a cryptosystem are con dentiality (Eve does not get information about the message). data integrity (Eve cannot alter the message). authentication (Bob knows for sure that the message comes from Alice).will consider the security requirements. • then three alternative functions used: – message encryption. – message authentication code (MAC). – hash function. Fall Chapter 11 – Message Authentication and. Hash Functions. Dr. Lo'ai Tawalbeh. Computer Engineering Department. Jordan University of Science and . Abstract. We will discuss. • Cryptographic hash functions. • Message authentication codes. – HMAC and CBC-MAC. • Digital signatures. 2. Message authentication and hash functions. COMP Message authentication . Message (or document) is authentic if. • It is genuine and. • came from its. MAC functions hash based block cipher based. -- Digital signatures. (c) Levente Buttyán ([email protected]). Protocols (message authentication, session key. Abstract. The use of cryptographic hash functions like MD5 or SHA for message authentication has become a standard approach in many Internet applications. A cryptographic hash function provides message integrity and authentication. □ A function is used to compute a short. `fingerprint' of the data; if the data is. Hash Functions (and Message Authentication Codes). Guarantee integrity of information after the application of the function. A cryptographic. Message Authentication - Learn Cryptography in simple and easy steps. Origin of Cryptography Hash functions, Message Authentication, Cryptography Digital. -

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