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Topic: Cryptographic hash

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	Hash function - Wikipedia, the free encyclopedia
		Cryptographic hash functions such as MD5 are commonly used as stock hash functions.
		Hash functions that are truly random with uniform output (including most cryptographic hash functions) yield good performance because, on average, only one or two probes will be needed (depending on the load factor).
		universal hashing by stinson from university of nabraska lincoln
	en.wikipedia.org /wiki/Hash_function (1194 words)

	Cryptographic hash function - Wikipedia, the free encyclopedia
		In cryptography, a cryptographic hash function is a hash function with certain additional security properties to make it suitable for use as a primitive in various information security applications, such as authentication and message integrity.
		A typical use of a cryptographic hash would be as follows: Alice poses to Bob a tough math problem and claims she has solved it.
		Such file hashes are often the top hash of a hash list or a hash tree which allows for additional benefits.
	en.wikipedia.org /wiki/Cryptographic_hash_function (1435 words)

	.:: General Purpose Hash Function Algorithms - By Arash Partow ::.
		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.
		Cryptographic hash functions are used to hash user's passwords and have the hash of the passwords stored on a system rather than having the password itself stored.
		An empirical result which demonstrated the distributive abilities of the hash algorithm was obtained using a hash-table with 100003 buckets, hashing The Project Gutenberg Etext of Webster's Unabridged Dictionary, the longest encountered chain length was 7, the average chain length was 2, the number of empty buckets was 4579.
	www.partow.net /programming/hashfunctions (1394 words)

	Verifyle :: Background :: The Idea (Site not responding. Last check: 2007-11-03)
		A hash function is a function that converts an input from a (typically) large domain into an output in a (typically) smaller range (the hash value, often a subset of the integers).
		Hash functions vary in the domain of their inputs and the range of their outputs and in how patterns and similarities of input data affect output data.
		A good hash function is one that experiences few hash collisions in the expected domain of strings it will have to deal with; i.e.
	www.verifyle.com /02020.php (602 words)

	PEP 247 -- API for Cryptographic Hash Functions
		Hash function modules define one variable: digest_size An integer value; the size of the digest produced by the hashing objects created by this module, measured in bytes.
		Hashing objects require a single attribute: digest_size This attribute is identical to the module-level digest_size variable, measuring the size of the digest produced by the hashing object, measured in bytes.
		If the hash has a variable output size, this output size must be chosen when the hashing object is created, and this attribute must contain the selected size.
	www.python.org /peps/pep-0247.html (834 words)

	Cryptographic hash function
		A cryptographic hash function is a hash function with certain additional security properties.
		A typical use of a crytographic hash would be as follows: Alice poses to Bob a tough math problem and claims she has solved it.
		SHA-1 and MD5 are the most commonly used cryptographic hash functions.
	guajara.com /wiki/en/wikipedia/c/cr/cryptographic_hash_function.html (306 words)

	RSA Security - 2.1.6 What is a hash function?
		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.
		A hash function H is said to be one-way if it is hard to invert, where ``hard to invert'' means that given a hash value h, it is computationally infeasible to find some input x such that H(x) = h.
		Since hash functions are generally faster than encryption or digital signature algorithms, it is typical to compute the digital signature or integrity check to some document by applying cryptographic processing to the document's hash value, which is small compared to the document itself.
	www.rsasecurity.com /rsalabs/node.asp?id=2176 (546 words)

	Hash Integrity - monotone documentation
		Some proponents of a competing, proprietary version control system have suggested, in a usenix paper, that the use of a cryptographic hash function such as sha1 as an identifier for a version is unacceptably unsafe.
		The fanciful val1 hash presented in the paper does not have such a property — flipping its first bit when all the rest are zero causes no change to any of the 160 output bits — and is completely unsuited for use as a cryptographic hash, regardless of the general shape of its probability distribution.
		Therefore the vulnerability is not that the hash might suddenly cease to address benign blocks well, but merely that additional security precautions might become a requirement to ensure that blocks are benign, rather than malicious.
	www.venge.net /monotone/docs/Hash-Integrity.html (961 words)

	Cryptography (Site not responding. Last check: 2007-11-03)
		Associated fields are steganography — the study of hiding the very existence of a message, and not necessarily the contents of the message itself (for example, microdots, or invisible ink) — and traffic analysis, which is the analysis of patterns of communication in order to learn secret information.
		A cryptanalyst might appear to be the natural adversary of a cryptographer, and to an extent this is true: one can view this contest all through the history of cryptography.
		Cryptographic hash functions produce a hash of a message.
	www.worldhistory.com /wiki/C/Cryptography.htm (2408 words)

	Cryptographic hash functions (Site not responding. Last check: 2007-11-03)
		Cryptographic hash functions are typically used to compute a message digest when making a digital signature.
		A hash 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.
	www.pvv.ntnu.no /~asgaut/crypto/thesis/node19.html (272 words)

	LavaRnd Digital Blender Algorithm
		The 20 octets of data produced by a given xor-rotate and fold operation is xor-ed with the 20 octets produced by the next SHA-1 cryptographic hash operation to produce 20 octets of random numbers.
		That is, the output from the 1st xor-rotate and fold operation is xor-ed with the output from the 2nd SHA-1 cryptographic hash operation yielding 20 octets of random numbers.
		The 20 octets of a given SHA-1 cryptographic hash operation is xor-ed with the 20 octets produced by the previous xor-rotate and fold operation yielding 20 octets of random numbers.
	www.lavarnd.org /what/digital-blender.html (505 words)

	Q94: What is a Hash Function? (Site not responding. Last check: 2007-11-03)
		A hash function H is a transformation that takes a variable-size input m and returns a fixed-size string, which is called the hash value h (that is, h = H(m)).
		The hash value represents concisely the longer message or document from which it was computed; one can think of a message digest as a "digital fingerprint" of the larger document.
		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.
	www.x5.net /faqs/crypto/q94.html (311 words)

	Hash Function Workshop
		Recently a team of researchers reported that the SHA-1 function offers significantly less collision resistance than could be expected from a cryptographic hash function of its output size.
		NIST plans to host a Cryptographic Hash Workshop on Oct. 31-Nov. 1, 2005 to solicit public input in how best to respond to the current state of research in this area.
		Clarify the properties of unkeyed cryptographic hash functions required for different applications.
	www.csrc.nist.gov /pki/HashWorkshop (156 words)

	RFC 2104 (rfc2104)
		Definition of HMAC The definition of HMAC requires a cryptographic hash function, which we denote by H, and a secret key K. We assume H to be a cryptographic hash function where data is hashed by iterating a basic compression function on blocks of data.
		We recommend that the output length t be not less than half the length of the hash output (to match the birthday attack bound) and not less than 80 bits (a suitable lower bound on the number of bits that need to be predicted by an attacker).
		The construction is independent of the details of the particular hash function H in use and then the latter can be replaced by any other secure (iterative) cryptographic hash function.
	www.cse.ohio-state.edu /cgi-bin/rfc/rfc2104.html (1922 words)

	ipedia.com: Cryptographic hash function Article (Site not responding. Last check: 2007-11-03)
		In cryptography, a cryptographic hash function is a hash function with certain additional security properties to make it suitable for use as a primitive in various information security applications, s...
		A hash function takes a long string (or message) of any length as input and produces a fixed length string as output; not all such are suitable for use in cryptography.
		Hash functions can also be used in the generation of pseudorandom bits, if they meet some additional, statistical, tests.
	www.ipedia.com /cryptographic_hash_function.html (1112 words)

	Make your software behave: Cryptography essentials (Site not responding. Last check: 2007-11-03)
		However, with a good cryptographic hashing function, it should be extremely difficult in practice to find two intelligible strings that hash to the same value.
		Cryptographic hash functions can be used as drop-in replacements for old style checksum algorithms.
		A digital signature for a document is usually constructed by cryptographically hashing the document, and then encrypting the hash using a private key.
	www-128.ibm.com /developerworks/java/library/s-hashing (3518 words)

	[No title]
		If you don't compute hash codes for each program or script that you execute and validate those hash codes periodically to ensure that those programs or scripts have not been changed, you really don't know whose code your computer is executing.
		One method to increase the data security provided by hash code and signature validation is to attach a ROM storage device to the computer to store sensitive data such as authentic hash codes or a key used for verifying signatures.
		A keyed hash code algorithm, like those derived from KeyedHashAlgorithm, would also add extra data security since an attacker would have to capture not only the secret key used with the AsymmetricAlgorithm to apply a valid signature to their replacement hash codes, but also the key used in the KeyedHashAlgorithm to compute the hash codes.
	msdn.microsoft.com /msdnmag/issues/02/09/ASPNETHashAlgorithms/default.aspx (2812 words)

	Cryptography Article, Cryptography Information (Site not responding. Last check: 2007-11-03)
		Associated fields are steganography — the study of hiding thevery existence of a message, and not necessarily the contents ofthe message itself (for example, microdots, or invisible ink) — and traffic analysis,which is the analysis of patterns of communication in order to learn secret information.
		A cryptanalyst might appear to be the natural adversary of a cryptographer, and to an extent this is true: one can view thiscontest all through the history of cryptography.However, it is possible, in fact preferable, to interpret the two roles as complementary: a thorough understanding ofcryptanalysis is necessary to create secure cryptography.
		It is well that much progress has been made in a short time; popular applications such as the Internet and mobile phones haverepositioned cryptography, historically the sole province of a few groups with exceptional needs for secrecy, into a mainstreamtechnology on which millions rely.
	www.anoca.org /key/ciphers/cryptography.html (2136 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 cryptographic pseudorandom number generator is a random number generator where it is intractible to deduce the generator's internal state given any number of its results.
	burtleburtle.net /bob/hash (1349 words)

	An Illustrated Guide to Cryptographic Hashes
		A "hash" (also called a "digest", and informally a "checksum") is a kind of "signature" for a stream of data that represents the contents.
		If the hash algorithm is properly designed and distributes the hashes uniformly over the output space, "finding a hash collision" by random guessing is exceedingly unlikely (it's more likely that a million people will correctly guess all the California Lottery numbers every day for a billion trillion years).
		As we've mentioned several times, "collisions" play a central role in the usefulness of a cryptographic hash, mainly in the sense that the easier it is to find a collision, the less useful the hash is. Some algorithms are better than others at avoiding collisions, and this is measured by three related attributes.
	www.unixwiz.net /techtips/iguide-crypto-hashes.html (3052 words)

	SHA-1 : SHA
		SHA-1 (Secure Hash Algorithm) is a message digest algorithm (and cryptographic hash function) designed by the National Security Agency (NSA) and published by the National Institute of Standards and Technology (NIST).
		It produces a 160-bit digest from a message with a maximum size of 2^64 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.
		These new hash functions have not yet received as much scrutiny by the public cryptographic community as SHA-1 has, and so their cryptographic security isn't yet as assured.
	www.fastload.org /sh/SHA.html (485 words)

	Wikipedia: Cryptographic hash function
		A cryptographic hash function is a hash function which has the following properties,
		Because of the birthday paradox this means the hash function has to have a larger image than is required by being preimage-resistant.
		See also: Topics in cryptography, cryptography, hash function.
	www.factbook.org /wikipedia/en/c/cr/cryptographic_hash_function.html (105 words)

	Cryptographic Algorithms (Site not responding. Last check: 2007-11-03)
		There are several possible arrangements; the general idea is that the hash function is used as a random number generator, and the hash value is xored with the data to be encrypted.
		When all bytes of the hash value have been used, a new hash value is obtained by modifying the key (or whatever was hashed) somehow, and taking a hash of that.
		SHA (Secure Hash Algorithm) (also SHS, Secure Hash Standard): This is a cryptographic hash algorithm published by the United States Government.
	starship.python.net /ssh/java/Cryptographic_algorithms.html (2388 words)

	Cryptographic Algorithms
		SHA-1 (Secure Hash Algorithm) (also SHS, Secure Hash Standard): This is a cryptographic hash algorithm published by the United States Government.
		Cryptographic systems need cryptographically strong (pseudo) random numbers that cannot be guessed by an attacker.
		are all good sources of randomness when processed with a suitable cryptographical hash function.
	www.crazylinux.net /mirrors/www.ssh.fi/algorithms.htm (6453 words)

	SSH : Support : Cryptography A-Z : Algorithms : Cryptographic Hash Functions
		Cryptographic hash functions are used in various contexts, for example to compute the message digest when making a digital signature.
		It produces a 160 bit hash value from an arbitrary length string.
		MD5 (Message Digest Algorithm 5) is a cryptographic hash algorithm developed at RSA Laboratories.
	www.ssh.fi /support/cryptography/algorithms/hash.html (302 words)

	Happy Happy Joy Joy (was: On to Hydro) (Site not responding. Last check: 2007-11-03)
		Hashtable hash >functions are used only for searching, whereas cryptographic hash >functions are used for integrity checking and identification.
		There are algorithms (I am told) for building "perfect hashes", where each input generates a different hash output.
		When used with a hash table, the birthday problem causes some chains to have several members while other chains are empty.
	www.eros-os.org /pipermail/e-lang/2000-August/003793.html (472 words)

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