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Journal ArticleDOI

A remark on hash functions for message authentication

01 Feb 1989-Computers & Security (Elsevier Advanced Technology)-Vol. 8, Iss: 1, pp 55-58
TL;DR: It is shown that a proposed method for using hash functions does not provide a secure non-repudiation service.
About: This article is published in Computers & Security.The article was published on 1989-02-01. It has received 6 citations till now. The article focuses on the topics: Hash chain & Hash function.
Citations
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Journal ArticleDOI
TL;DR: The landward transgression of man-groves into saltmarsh environments in the estuaries of south-east Australia over the last five decades is established as a widespread trend through a review of a number of independent studies as discussed by the authors.
Abstract: The landward transgression of man- groves into saltmarsh environments in the estuaries of south-east Australia over the last five decades is established as a widespread trend through a review of a number of independent studies. This process is occurring in a range of geomorphic settings, and in some cases reversing the direction of longer-term vegetation change. Several hypotheses are advanced to explain this occurrence, including increases in rainfall, revegetation of areas cleared for agriculture, altered tidal regimes or estuary water levels, and increases in nutrient levels and sedimentation.

246 citations

Patent
Kevin W. Kingdon1
02 Nov 1993
TL;DR: In this article, a method and apparatus for message packet authentication to prevent the forging of message packets is presented, where a portion of the message digest, referred to as the signature, is then appended to the actual message when it is sent over the wire.
Abstract: The present invention provides a method and apparatus for message packet authentication to prevent the forging of message packets. A portion of the message digest, referred to as the signature, is then appended to the actual message when it is sent over the wire (205). The receiving station strips the signature from the message (208), preappends the same secret session key (209) and creates its own message digest (212). The signature of the digest created by the receiving station is compared to the signature of the digest appended by the sending station (213). If there is a match, an authentic message is assumed (214). If there is no match, the message is considered as invalid and discarded (216).

160 citations

Journal ArticleDOI
TL;DR: The model that physicochemical conditions control the intertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those strand- ing on mudflats, and the model that interspecific interaction with freeliving macroalgae (Hormosira banksii) re- duces the establishment of plant species was accepted.
Abstract: The upper and lower limits of the distribution of mature Avicennia marina lie between mean high water and mean sea level in open estuaries in southeastern Australia. Newly established seedlings are highly variable in abundance, but are rarely found in the saltmarsh or on mudflats. Their distribution is unlikely to be limited by dispersal because propagules disperse into the saltmarsh and to intertidal mudflats, but their establishment may be limited by physicochemical conditions, interspecific competition and predation. The model that physicochemical conditions control the intertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those strand- ing on mudflats. No seedlings established on saltmarsh sediments but similar numbers of seedlings established within light gaps in adult mangrove stands and on intertidal mudflats. The model that interspecific interaction with freeliving macroalgae (Hormosira banksii) re- duces the establishment of seedlings on mudflats covered with macroalgae or in stands with a ground cover of macroalgae was accepted. Under controlled conditions five times as many propagules established on cleared ground compared with ground covered with macroalgae. Predators also reduce seedling establishment, but the model that they preferentially act on propagules stranding on the mudflat was rejected. The low number of seedlings found on mudflats without macroalgae appears to relate to wave and current effects on establishment and the effects of waterlogging or fouling on survival.

146 citations

Journal ArticleDOI
01 Apr 2008-Oikos
TL;DR: A demonstration of non-additive and identity-dependent effects of detrital species mixing on soft-sediment communities suggests that predicted compositional changes to aquatic macrophyte communities, resulting from coastal development and climate change, will flow on to effect other components of the estuarine food-web.
Abstract: Accelerating rates of species extinction and invasion have sparked recent interest in how changes in plant community composition can be propagated through food webs. Research in this area has, however, been largely restricted to considerations of how detrital species mixing affects litter decay processes. The consequences of changing detrital resources for whole assemblages of sediment-dwelling invertebrates remain largely unknown. We manipulated the availability of three detrital sources, Avicennia marina leaves, Posidonia australis blades and Sargassum sp. thalli, on an Australian mudflat to test hypotheses about how changes in the type and number of macrophytes contributing to detrital resources might impact benthic invertebrate assemblages of estuarine soft-sediments. By controlling for changes in total detrital biomass and ensuring that each detrital source was present in two- and three-species mixes as well as monocultures, our experimental design was able to distinguish among effects of mixing, identity and biomass. Three months after detrital manipulation, macroinvertebrate abundance and species richness differed among treatments according to the biomass of detritus added and non-additive effects of detrital species mixing. Whereas the mixing of two detrital species generally had an antagonistic effect on macroinvertebrate abundance and richness, faunal assemblages did not appreciably differ between three-species mixes and monocultures. Generally negative effects of two-species mixes on macroinvertebrates were opposed by positive effects on microphytobenthos, an important food-source for many of the animals. Non-additive effects on sediment communities were particularly apparent when Sargassum sp., the most labile of the three detrital sources considered, was included in two-species mixes. This demonstration of non-additive and identity-dependent effects of detrital species mixing on soft-sediment communities suggests that predicted compositional changes to aquatic macrophyte communities, resulting from coastal development and climate change, will flow on to effect other components of the estuarine food-web.

24 citations

Journal ArticleDOI
TL;DR: An improved version of SFHA – 256 is proposed and analyzed using two parameters, namely the avalanche effect and uniform deviation, and it can be concluded that the newly proposed algorithm is more secure, efficient, and practical.
Abstract: —Recently, a fast and secure hash function SFHA – 256 has been proposed and claimed as more secure and as having a better performance than the SHA – 256. In this paper an improved version of SFHA – 256 is proposed and analyzed using two parameters, namely the avalanche effect and uniform deviation. The experimental results and further analysis ensures the performance of the newly proposed and improved SFHA-256. From the analysis it can be concluded that the newly proposed algorithm is more secure, efficient, and practical. Keywords —SHA-256, SFHA-256, Improved SFHA-256 1. I NTRODUCTION The hash function H accepts the variable-sized message M as input and outputs a fixed-size representation H(M) of M, which is sometimes called a message digest [1]. I.B. Damgard et.el., discussed the construction of hash functions and presented an efficient and much more secure scheme with the combination of RSA system with the collision free hash function based on fac-toring [2]. Hash functions for message authentications are proposed in [3]. A universal one-way hash function family is discussed in [4]. SHA-1 is a cryptographic hash function published by the National Institute of Standards and Technology (NIST). The three SHA algorithms are SHA-0, SHA-1, and SHA-2. The SHA-0 algorithm was not used in many applications. On the other hand, SHA-2 differs from the SHA-1 hash function. SHA-1 is the most widely used hash function. Several widely-used security ap-plications and protocols are based on SHA-1. In 2005, security flaws were identified in SHA-1 [5]. A prime motivation for the publication of the Secure Hash Algorithm was the Digital Signa-ture Standard. The Digital Signature Algorithm (DSA) is a United States Federal Government standard or FIPS for digital signatures. It was proposed by the National Institute of Standards and Technology (NIST) in August 1991 for use in their Digital Signature Standard (DSS). The ElGamal signature scheme is a digital signature scheme that is based on the difficulty of com-puting discrete logarithms. It was described by Taher ElGamal in 1984 [6]. The Elliptic Curve Digital Signature Algorithm (ECDSA) is a variant of the Digital Signature Algorithm (DSA) that uses Elliptic curve cryptography [7, 8]. Recently, Hassan. M. Elkamchouchi et el., proposed a fast and secure hash function (SFHA -

12 citations

References
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Journal ArticleDOI
TL;DR: An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key.
Abstract: An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: (1) Couriers or other secure means are not needed to transmit keys, since a message can be enciphered using an encryption key publicly revealed by the intented recipient. Only he can decipher the message, since only he knows the corresponding decryption key. (2) A message can be “signed” using a privately held decryption key. Anyone can verify this signature using the corresponding publicly revealed encryption key. Signatures cannot be forged, and a signer cannot later deny the validity of his signature. This has obvious applications in “electronic mail” and “electronic funds transfer” systems. A message is encrypted by representing it as a number M, raising M to a publicly specified power e, and then taking the remainder when the result is divided by the publicly specified product, n, of two large secret primer numbers p and q. Decryption is similar; only a different, secret, power d is used, where e * d ≡ 1(mod (p - 1) * (q - 1)). The security of the system rests in part on the difficulty of factoring the published divisor, n.

14,659 citations

Book ChapterDOI
01 Jan 1987
TL;DR: Simple identification and signature schemes which enable any user to prove his identity and the authenticity of his messages to any other user without shared or public keys are described.
Abstract: In this paper we describe simple identification and signature schemes which enable any user to prove his identity and the authenticity of his messages to any other user without shared or public keys. The schemes are provably secure against any known or chosen message attack if factoring is difficult, and typical implementations require only 1% to 4% of the number of modular multiplications required by the RSA scheme. Due to their simplicity, security and speed, these schemes are ideally suited for microprocessor-based devices such as smart cards, personal computers, and remote control systems.

4,193 citations

Book ChapterDOI
Ivan Damgård1
13 Apr 1987
TL;DR: The ability of a hash function to improve security and speed of a signature scheme is discussed: for example, it can combine the RSA-system with a collision free hash function based on factoring to get a scheme which is more efficient and much more secure.
Abstract: In this paper, we present a construction of hash functions. These functions are collision free in the sense that under some cryptographic assumption, it is provably hard for an enemy to find collisions. Assumptions that would be sufficient are the hardness of factoring, of discrete log, or the (possibly) more general assumption about the existence of claw free sets of permutations. The ability of a hash function to improve security and speed of a signature scheme is discussed: for example, we can combine the RSA-system with a collision free hash function based on factoring to get a scheme which is more efficient and much more secure. Also, the effect of combining the Goldwasser-Micali-Rest signature scheme with one of our functions is studied. In the factoring based implementation of the scheme using a k-bit modulus, the signing process can be speeded up by a factor roughly equal to kċO (log2(k)), while the signature checking process will be faster by a factor of O (log2(k)).

391 citations

Proceedings ArticleDOI
01 Apr 1984
TL;DR: This talk proves security under a black box model, that is, algorithms which call the encryption function via an oracle, and calculate the expected running time for a randomly chosen block cipher, which mirrors attacks on the system which do not rely on special properties of theryption function.
Abstract: Applying a one-way hash function is a useful preliminary to digitally signing a message, both for security and efficiency. Several proposals for building such a function out of DES have been shown to be insecure. This talk studies a proposal due to Davies, and provides some evidence for its security. We prove security under a black box model. That is, we consider algorithms which call the encryption function via an oracle, and calculate the expected running time for a randomly chosen block cipher. This mirrors attacks on the system which do not rely on special properties of the encryption function. Under this model, we show that, given Y, finding a message hashing to y requires 0(264) encryptions. However, if the opponent is also given some legitimately signed messages, a speedup is possible, proportional to the total length of such material. This can be foiled by adding a running count to each block. The resulting system provably requires O(264) steps to break, even given large amounts of signed material. By modifying the model, these results can be strengthened to show that tbe existence of weak keys and the complementation property of DES do not help the forger. Any successful attack would have to use more subtle properties of DES.

115 citations