One way hash functions are a major tool in cryptography. DES is the best known and most widely used encryption function in the commercial world today. Generating a one-way hash function which is secure if DES is a "good" block cipher would therefore be useful. We show three such functions which are secure if DES is a good random block cipher.

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One way hash functions and DES

Information Security has become an important issue in modern world as the popularity and infiltration of internet commerce and communication technologies has emerged, making them a prospective medium to the security threats. To surmount these security threats modern data communications uses cryptography an effective, efficient and essential component for secure transmission of information by implementing security parameter counting Confidentiality, Authentication, accountability, and accuracy. To achieve data security different cryptographic algorithms (Symmetric & Asymmetric) are used that jumbles data in to scribbled format that can only be reversed by the user that have to desire key. This paper presents a comprehensive comparative analysis of different existing cryptographic algorithms (symmetric) based on their Architecture, Scalability, Flexibility, Reliability, Security and Limitation that are essential for secure communication (Wired or Wireless).

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Symmetric Algorithm Survey: A Comparative Analysis

Multi-bit auxiliary information is hidden in imagery (e.g., digital photographs, video), using steganographic techniques. Such information can be used for various purposes, including identifying imagery as originating from a particular source, copy control, etc. In some embodiments, one image is encoded using data that is dependent on a second image.

Steganographically encoding a first image in accordance with a second image

An individual's speech sample, obtained for the purpose of speaker verification, is used to create a "protected" model of the speech. The protected model, which is stored in a database in association with a personal identifier for that individual, is arranged so that the characteristics of the individual's speech cannot be ascertained from the protected model, without access to an encryption key or other secured information stored in the system. (Fig. 1)

Speaker verification system and process.

Cryptographic hash functions are a useful building block for several cryptographic applications. The most important are certainly the protection of information authentication and digital signatures. This overview paper will discuss the deflnitions, describe some attacks on hash functions, and will give an overview of the existing practical constructions. it. Hash functions appeared in cryptographic literature when it was realized that encryption of information is not su-cient to protect its authenticity. The simplest example is the encryption with a block cipher in Electronic Code Book (ECB) mode, where every block is encrypted independently. It is clear that an active attacker can easily modify the order of the ciphertext blocks and hence of the corresponding plaintext blocks. It will be shown that cryptographic hash functions allow for e-cient constructions to protect authenticity with or without secrecy. In a flrst part of this overview paper, the deflnitions of several types of hash functions will be given, and the basic attacks on hash functions will be discussed. Then it will be explained brie∞y how they can be used to protect the integrity of information. The protection of software integrity will be treated as an example. Subsequently a general model is described and an extensive overview is given of the proposed schemes. Here a distinction will be made between hash functions with an without a secret key. Finally the conclusions will be presented. It will be assumed that the reader is familiar with the basic concepts of cryptography as explained in (39, 57, 84, 91, 93). Other overview papers on hash functions and authentication are (2, 16, 43, 95, 107, 120). 1 NFWO aspirant navorser, sponsored by the National Fund for Scientiflc Research (Belgium).

Cryptographic hash functions: an overview

Cryptography is the only known practical method for protecting information transmitted through potentially hostile environments, where it is either impossible or impractical to protect the information by conventional physical means. Also, damage resulting from message alteration, message insertion, and message deletion can be avoided. Administrative and physical security procedures often can provide adequate protection for offline data transport and storage. However, where file security methods are either nonexistent or weak, encryption may provide the most effective and economical protection. The authors gives an overview of cryptographic methods using symmetric and asymmetric algorithms and demonstrates why future cryptographic applications should use a hybrid approach, i.e., combination of symmetric and asymmetric (public key) methods. >

C.H. Meyer

Papers

Cryptography-a state of the art review