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Topic: SHA hash functions

	SHA hash functions at AllExperts
		SHA-1 is considered to be the successor to MD5, an earlier, widely-used hash function.
		SHA also internally use some additional variables such as length of the data compressed so far since that is needed for the length padding in the end.
		The SHA hash functions have been used as the basis for the SHACAL block ciphers.
	en.allexperts.com /e/s/sh/sha_hash_functions.htm (2451 words)

	sha hash functions - Article and Reference from OnPedia.com
		SHA-1 is considered to be the successor to MD5, an earlier, widely-used hash function.
		These new hash functions have not received as much scrutiny by the public cryptographic community as SHA-1 has, and so their cryptographic security is not yet as well-established.
		The SHA hash functions have been used as the basis for the SHACAL block ciphers.
	www.onpedia.com /encyclopedia/sha-hash-functions (2091 words)

	Hash Functions - CryptoDox
		It is often also called a "message digest." Hash functions are used for digital signatures such as RSA and DSA, but also for the construction of MACs (message authentication codes), the protection of passwords, and for the derivation of independent secret keys from a single master key.
		Cryptographic hash functions are an essential building block for applications that require data integrity, such as detectors of computer viruses, Internet security (for example PGP or IPSEC), and the security of electronic commerce and banking.
		A hash function must be a one-way function, which means that finding an input corresponding to a given output string is difficult: Even an opponent who wants to spend a significant amount of money, say $10 million, will have a negligible success probability.
	www.cryptodox.com /index.php?title=Hash_Functions (247 words)

	Pluto Scarab â” Hash Functions (Site not responding. Last check: 2007-10-24)
		Hash functions are functions that map a bit vector to another bit vector, usually shorter than the original vector and usually of fixed length for a particular function.
		Hash functions play an important role in encryption because it is their properties that cause the encrypted data to be unreadable and the original data to be unrecoverable from the encrypted data without the decryption key.
		If a hash function is to be used for cryptography or for fast table lookup where the nature of the keys is unknown, the one-way property is a requirement.
	bretm.home.comcast.net /hash (841 words)

	Cryptographic Hash Functions (Site not responding. Last check: 2007-10-24)
		A simple hash function is to give each letter of the alphabet a number, then add up all the numbers in the plaintext.
		The function compresses the bits of a message to a fixed-size hash value in a way that distributes the possible messages evenly among the possible hash values.
		A cryptographic hash function does this in a way that makes it extremely difficult to come up with a message that would hash to a particular hash value.
	members.shaw.ca /fclarke/crypto/Crypto1-172.htm (254 words)

	Analysis of Hash Functions with Methods to Optimize Attack Complexity : HITACHI-SDL
		The conference focused on hash functions which can be used for message authentication and random numbers generations, etc. In response to the recent announcement of a theoretical attack on SHA-1 hash function, hash functions were discussed from various angles, such as design, evaluation, and deployment of them.
		A hash function is an algorithm with the input of the arbitrary length and the output of the fixed length (hash value).
		One of the most important security notion for hash functions is collision resistance, which means that it is computationally difficult to find a pair of messages producing the same output of the hash function.
	www.sdl.hitachi.co.jp /english/news/2005/crpt_hash05 (493 words)

	Certicom \| Resources \| FAQs \| MD5, SHA-0 and hash collisions
		A hash function is designed to generate a unique fingerprint of fixed size of any piece of data regardless of the length of the input.
		Hash functions are designed so that it is impossible, in practice, to find a hash collision.
		Hash functions for which collisions can be found should not be used in signature schemes.
	www.certicom.com /index.php?action=res,md5_faq (734 words)

	[No title] (Site not responding. Last check: 2007-10-24)
		In IKEv2 with public-key certificates, a hash function is used for similar purposes, both for identifying the sender's public key and in identifying the trust roots.
		In both of these cases, hash functions are used to obscure the IP addresses used by the initiator and/or the responder.
		Hashes in IPsec AH uses hash functions for authenticating packets; the same is true for ESP when ESP is using its own authentication.
	www.ietf.org /internet-drafts/draft-hoffman-ike-ipsec-hash-use-03.txt (2895 words)

	Encryption - SHA (Site not responding. Last check: 2007-10-24)
		SHA is the short form of Secure Hashing Algorithm.
		SHA is a family of composed of a related cryptographic hash functions.
		The SHA algorithms are published as a standard of the United States government.
	www.cs.usask.ca /work/408/06group6/sha.html (816 words)

	Hash - CompWisdom (Site not responding. Last check: 2007-10-24)
		Since hash functions are generally faster than digital signature algorithms, it is typical to compute the digital signature to some document by computing the signature on the document's hash value, which is small compared to the document itself.
		Hash functions with just this property have a variety of general computational uses, but when employed in cryptography the hash functions are usually chosen to have some additional properties.
		When algorithms which contain hash functions are analyzed it is generally assumed that hash functions have a complexity of O(1), that is why look-ups for data in a hash-table are said to be of O(1) complexity, where as look-ups of data in maps (Red-Black Trees) are said to be of O(logn) complexity.
	www.compwisdom.com /topics/Hash (3037 words)

	Hash Functions and Block Ciphers
		A hash function for hash table lookup should be fast, and it should cause as few collisions as possible.
		If you know the keys you will be hashing before you choose the hash function, it is possible to get zero collisions -- this is called perfect hashing.
		A block cipher is a reversible function g:KxB->C, which maps a key in K and a block in B into a block in C. Usually B and C are the same set, so the block cipher permutes B in a key-specific way.
	www.burtleburtle.net /bob/hash (1349 words)

	Cryptographic Hashes
		A typical non-cryptographic use for hash functions is for validating that the contents of a file have not been changed in transit.
		The property of good hash functions that there is even probability that each bit in the output is a 0 or 1 for an arbitrary input makes hashes particularly good for human-based content validation.
		Collisions for Hash Functions MD4, MD5, HAVAL-128 and RIPEMD by Xiaoyun Wang, Dengguo Feng, Xuejia Lai, and Hongbo Yu, August 2004.
	www.vpnc.org /hash.html (1933 words)

	Hash Functions (Linktionary term)
		Hash functions are one-way, meaning that it is easy to compute the message digest but very difficult to revert the message digest back to the original plaintext (e.g., imagine trying to put a smashed pumpkin back to exactly the way it was).
		HMAC (Hashed Message Authentication Code) is a core protocol that is considered essential for security on the Internet along with IPSec, according to RFC 2316 (Report of the IAB, April 1998).
		It is not a hash function, but a mechanism for message authentication that uses either MD5 or SHA-1 hash functions in combination with a shared secret key (as opposed to a public/private key pair).
	www.linktionary.com /h/hash_function.html (1099 words)

	SHA hash functions - Wikipedia, the free encyclopedia
		Many of the applications that use cryptographic hashes, such as password storage or document signing, are only minimally affected by a collision attack.
		Constructing a password that works for a given account requires a preimage attack, and access to the hash of the original password (typically in the shadow file) which may or may not be trivial.
		NIST has published four additional hash functions in the SHA family, each with longer digests, collectively known as SHA-2.
	en.wikipedia.org /wiki/SHA_hash_functions (2051 words)

	A Low Complexity Fix for MD5
		The cryptographic hash function MD5 has become unusable for cryptographic and authentication purposes because hash collisions have been found that open up MD5 hashed data to undetectable alteration.
		birthday attack, the hash function output (in bits) must be at least twice as large as what is required for preimage-resistance.
		An ideal hash function would be maximally "boring": it would have no interesting properties such as length extension, and the only interesting way it would differ from a random function would be in that it was deterministic and efficiently computable.
	hireme.geek.nz /MD5-fix.html (1210 words)

	Sha-1 Cryptanalysis - GovernmentSecurity.org
		One-way hash functions are supposed to have two properties.
		Most of the hash functions we have, and all the ones in widespread use, are based on the general principles of MD4.
		Hash functions are the least-well-understood cryptographic primitive, and hashing techniques are much less developed than encryption techniques.
	www.governmentsecurity.org /forum/index.php?showtopic=13798 (1280 words)

	Hash Functions
		A hash function is a function H(s), where s is a string of bits of any length and the function value is a number in a specified range--usually a 128 or 160 bit number in cryptographic applications.
		In general, for a good hash function, you want all possible function values to be about equally probable if you choose an s at random.
		For a good hash function, there should be no easier way to find M1 and M2 such that h(M1)=h(M2)) and any method that is easier is considered to be a theoretical way of breaking that hash function.
	www2.hawaii.edu /~wes/ICS623/Assignments/SHA-1.html (2044 words)

	MD5z.com :: SHA Hash Functions
		SHA-0 and SHA-1 produce a 160-bit digest from a message with a maximum size of 264 bits, and is based on principles similar to those used by Professor Ronald L. Rivest of MIT in the design of the MD4 and MD5 message digest algorithms.
		At CRYPTO 98, two French researchers presented an attack on SHA-0 (Chabaud and Joux, 1998): collisions can be found with complexity 261; fewer than the 280 for an ideal hash function of the same size.
		SHA also internally use some additional variables such as length of the data compressed so far since that is needed for the length padding in the end.
	www.md5z.com /sha-hash-functions/index.html (1667 words)

	Upsilon Pi Epsilon » HMAC, The Keyed Hash-Based MAC Function (Site not responding. Last check: 2007-10-24)
		An example of a secure hash function (which is commonly used in HMAC implementations) is SHA-14.
		Furthermore, there are several generations of SHA hashing functions (SHA-256, SHA-384, and SHA-512) which are currently available but not very widely used as their added security is not yet believed to be needed in everyday transactions.
		HMAC has all of the general properties of a MAC function; this means that HMAC is suitable anytime senders and receivers wish to guarantee integrity between sender and receiver.
	the.jhu.edu /upe/2002/01/18/hmac1-the-keyed-hash-based-mac-function (656 words)

	Reference.com/Encyclopedia/SHA hash functions
		The SHA (Secure Hash Algorithm) hash functions refer to five FIPS-approved algorithms for computing a condensed digital representation (known as a message digest) that is, to a high degree of probability, unique for a given input data sequence (the message).
		These algorithms are called “secure” because (in the words of the standard), “for a given algorithm, it is computationally infeasible 1) to find a message that corresponds to a given message digest, or 2) to find two different messages that produce the same message digest.
		It was considered to be the successor to MD5, an earlier, widely-used hash function.
	www.reference.com /browse/wiki/SHA_hash_functions (2688 words)

	Opinion: Cryptanalysis of MD5 and SHA: Time for a new standard
		One-way hash functions are a cryptographic construct used in many applications.
		Breaking a hash function means showing that either -- or both -- of those properties aren't true.
		Cryptanalysis of the MD4 family of hash functions has proceeded in fits and starts over the past decade or so, with results against simplified versions of the algorithms and partial results against the whole algorithms.
	www.computerworld.com /printthis/2004/0,4814,95343,00.html (788 words)

	MD5 - openSUSE
		In cryptography, MD5 (Message-Digest algorithm 5) is a widely-used cryptographic hash function with a 128-bit hash value.
		While this was not an attack on the full MD5 hash function, it was close enough for cryptographers to recommend switching to a replacement, such as WHIRLPOOL, SHA-1 or RIPEMD-160.
		The size of the hash — 128 bits — is small enough to contemplate a brute force birthday attack.
	en.opensuse.org /MD5 (1167 words)

	HASH Functions (Site not responding. Last check: 2007-10-24)
		A "Hash function" is a complex encryption algorithm used primarily in cryptography, and is like a shortened version of full-scale encryption.
		Hash algorithms are written to avoid collisions, but some, such as MD5 - have been shown to have collisions.
		Hash algorithms take a long string (or message) of any length as input and produce a fixed length string as output; not all such are suitable for use in cryptography.
	www.infocellar.com /networks/Security/hash.htm (1512 words)

	RFC 2202 (rfc2202) - Test Cases for HMAC-MD5 and HMAC-SHA-1
		HMAC-MD5 and HMAC-SHA-1 are two constructs of the HMAC [HMAC] message authentication function using the MD5 [MD5] hash function and the SHA-1 [SHA] hash function.
		Introduction The general method for constructing a HMAC message authentication function using a particular hash function is described in section 2 of [HMAC].
		Note that these functions are meant to be simple and easy to understand; they are not optimized in any way.
	www.faqs.org /rfcs/rfc2202.html (629 words)

	Enterprise IT Planet: Security Resources for the Enterprise IT Professional (Site not responding. Last check: 2007-10-24)
		So if we store the SHA-1 hash of user passwords in our databases, we can authenticate user logins by first computing the SHA-1 hash of the password supplied by the user who is attempting to log in and then comparing the hash against the copy stored in the database.
		Hashes are also often used to sign big file downloads to prove they have not been tampered.
		Function getShaHash accepts one parameter, a C string, and returns the BASE64 encoded SHA-1 hash of that string as a newly allocated C++ STL string object.
	www.enterpriseitplanet.com /security/features/print.php/2169511 (2082 words)

	Hash Functions - Crypto++ Wiki
		Hash functions provide a way of creating a digital fingerprint for data.
		The function substitutes and transposes (chops or mixes) the data to create the fingerprint, often called a hash value or digest.
		Note that the output is encoded as hex which is why the output buffer must be two times the size of the MD5 digest.
	www.cryptopp.com /wiki/Hash (212 words)

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