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Hashing
Hash, hashes, hash mark, or hashing may refer to: Substances * Hash (food), a coarse mixture of ingredients * Hash, a nickname for hashish, a cannabis product Hash mark *Hash mark (sports), a marking on hockey rinks and gridiron football fields * Hatch mark, a form of mathematical notation * Number sign (#), also known as the hash, hash mark, or (in American English) pound sign * Service stripe, a military and paramilitary decoration * Tally mark, a counting notation Computing * Hash function, an encoding of data into a small, fixed size; used in hash tables and cryptography * Hash table, a data structure using hash functions * Cryptographic hash function, a hash function used to authenticate message integrity * URI fragment, in computer hypertext, a string of characters that refers to a subordinate resource * Geohash, a spatial data structure which subdivides space into buckets of grid shape * Hashtag, a form of metadata often used on social networking websites * hash (Unix), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Table
In computing, a hash table, also known as hash map, is a data structure that implements an associative array or dictionary. It is an abstract data type that maps keys to values. A hash table uses a hash function to compute an ''index'', also called a ''hash code'', into an array of ''buckets'' or ''slots'', from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. Ideally, the hash function will assign each key to a unique bucket, but most hash table designs employ an imperfect hash function, which might cause hash ''collisions'' where the hash function generates the same index for more than one key. Such collisions are typically accommodated in some way. In a well-dimensioned hash table, the average time complexity for each lookup is independent of the number of elements stored in the table. Many hash table designs also allow arbitrary insertions and deletions of key–value pairs, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Function
A hash function is any function that can be used to map data of arbitrary size to fixed-size values. The values returned by a hash function are called ''hash values'', ''hash codes'', ''digests'', or simply ''hashes''. The values are usually used to index a fixed-size table called a ''hash table''. Use of a hash function to index a hash table is called ''hashing'' or ''scatter storage addressing''. Hash functions and their associated hash tables are used in data storage and retrieval applications to access data in a small and nearly constant time per retrieval. They require an amount of storage space only fractionally greater than the total space required for the data or records themselves. Hashing is a computationally and storage space-efficient form of data access that avoids the non-constant access time of ordered and unordered lists and structured trees, and the often exponential storage requirements of direct access of state spaces of large or variable-length keys. Use of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash House Harriers
The Hash House Harriers (HHH or H3) is an international group of non-competitive running social clubs. An event organized by a club is known as a Hash or Run, or a Hash Run. A common denominal verb for this activity is Hashing, with participants calling themselves Hashers. Male members are referred to as Harriers, which females are known as Hariettes. The Hash is humorously known as ''A Drinking Club With A Running Problem,'' with the preferred beverage of consumption being beer. History Hashing originated in December 1938 in Kuala Lumpur, Selangor, then in the Federated Malay States (now Malaysia). A group of British immigrants began meeting on Friday evenings prior to the war (1938-1941), but switched to Monday evenings (starting in 1946) to run, in a fashion patterned after the traditional British paper chase or "Hare & Hounds". Apart from the excitement of chasing the Hare and finding the trail, Harriers reaching the end of the trail would partake of beer, ginger beer, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptographic Hash Function
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with fixed size of n bits) that has special properties desirable for cryptography: * the probability of a particular n-bit output result (hash value) for a random input string ("message") is 2^ (like for any good hash), so the hash value can be used as a representative of the message; * finding an input string that matches a given hash value (a ''pre-image'') is unfeasible, unless the value is selected from a known pre-calculated dictionary (" rainbow table"). The ''resistance'' to such search is quantified as security strength, a cryptographic hash with n bits of hash value is expected to have a ''preimage resistance'' strength of n bits. A ''second preimage'' resistance strength, with the same expectations, refers to a similar problem of finding a second message that matches the given hash value when one message is already known; * finding any pair of different messa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Password Hash
In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a master key, a password, or a passphrase using a pseudorandom function (which typically uses a cryptographic hash function or block cipher). KDFs can be used to stretch keys into longer keys or to obtain keys of a required format, such as converting a group element that is the result of a Diffie–Hellman key exchange into a symmetric key for use with AES. Keyed cryptographic hash functions are popular examples of pseudorandom functions used for key derivation. History The first deliberately slow (key stretching) password-based key derivation function was called "crypt" (or "crypt(3)" after its man page), and was invented by Robert Morris in 1978. It would encrypt a constant (zero), using the first 8 characters of the user's password as the key, by performing 25 iterations of a modified DES encryption algorithm (in which a 12-bit numbe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geohash
Geohash is a public domain geocode system invented in 2008 by Gustavo NiemeyerEvidences at the Wayback Machine: labix.org in 2008, the G. Niemeyer's blog announcing Geohash *an article about Geohash witnessing and citing G. Niemeyer works, before 2012 G. Niemeyer's post at forums.geocaching.com announcing Geohash in Feb. 2008 which encodes a geographic location into a short string of letters and digits. Similar ideas were introduced by G.M. Morton in 1966.G. M. Morton (196''"A Computer Oriented Geodetic Data Base and a New Technique in File Sequencing"''. Report in IBM Canada. It is a hierarchical spatial data structure which subdivides space into buckets of grid shape, which is one of the many applications of what is known as a Z-order curve, and generally space-filling curves. Geohashes offer properties like arbitrary precision and the possibility of gradually removing characters from the end of the code to reduce its size (and gradually lose precision). Geohashing guarantees th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zobrist Hashing
Zobrist hashing (also referred to as Zobrist keys or Zobrist signatures Bruce Moreland/ref>) is a hash function construction used in computer programs that play abstract board games, such as chess and Go, to implement transposition tables, a special kind of hash table that is indexed by a board position and used to avoid analyzing the same position more than once. Zobrist hashing is named for its inventor, Albert Lindsey Zobrist.Albert Lindsey Zobrist''A New Hashing Method with Application for Game Playing'' Tech. Rep. 88, Computer Sciences Department, University of Wisconsin, Madison, Wisconsin, (1969). It has also been applied as a method for recognizing substitutional alloy configurations in simulations of crystalline materials. Zobrist hashing is the first known instance of the generally useful underlying technique called tabulation hashing. Calculation of the hash value Zobrist hashing starts by randomly generating bitstrings for each possible element of a board game, i.e. f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash (Unix)
hash is a command (computing), command on Unix and Unix-like operating systems that prints the location information for the commands found. The command has also been ported to the IBM i operating system. Syntax $ hash [name] Description When the user gives a command, the shell searches for the command in the path specified in the PATH (variable), PATH environmental variable and stores the location in the hash. This command can be used to search for the command given. The command is built into the shell. C shell implements this command in a different way. Options The following options are supported. ;name: Searches the PATH environmental variable for the name given Exit Status This command returns the following exit values: ;0: Successful completion ;1: An Error occurred Examples $ hash Print the hash table. $ hash cat Searches for command cat in the path specified by PATH environmental variable; if found, adds it to the hash. See also * Find (Unix), find * Unix s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash (EP)
'' ' (read as "hash") is the second extended play by South Korean girl group Loona. It was released on February 5, 2020, by Blockberry Creative and distributed by Kakao M. Background On March 31, 2019, a teaser titled "#" was released on the group's official YouTube channel. The clip looks back to Loona's previous releases and teaser films and ends with the word "burn". It also features imagery of butterflies, as well as the symbols "++" and "xx". On May 31, a second teaser was released titled "La Maison Loona", with the phrase "delayed but someday" showed at the end. On December 13, a teaser titled "#1" was released. On December 31, an image teaser was released. On January 8, 2020, it was announced that member HaSeul would halt activities with the group due to health concerns. On January 10, a second teaser was released titled "#2", setting the release date to February 5. On January 13, individual teasers started to being released, starting with member Olivia Hye and ending wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Ledger
A distributed ledger (also called a shared ledger or distributed ledger technology or DLT) is the consensus of replicated, shared, and synchronized digital data that is geographically spread (distributed) across many sites, countries, or institutions. In contrast to a centralized database, a distributed ledger does not require a central administrator, and consequently does not have a single (central) point-of-failure. In general, a distributed ledger requires a peer-to-peer (P2P) computer network and consensus algorithms so that the ledger is reliably replicated across distributed computer nodes (servers, clients, etc.). The most common form of distributed ledger technology is the blockchain (commonly associated with the Bitcoin cryptocurrency), which can either be on a public or private network. Infrastructure for data management is a common barrier to implementing DLT. In some cases, where the distributed digital information functions as an accounting journal rather than an a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hashgraph
Hashgraph is a distributed ledger technology that has been described as an alternative to blockchains. The hashgraph technology is currently patented, is used by the public ledger Hedera, and there is a grant to implement the patent as a result of the Apache 2.0's Grant of Patent License (provision #3) so long as the implementation conforms to the terms of the Apache license. The native cryptocurrency of the Hedera Hashgraph system is HBAR. Unlike blockchains, hashgraphs do not bundle data into blocks or use miners to validate transactions. Instead, hashgraphs use a "gossip about gossip" protocol where the individual nodes on the network "gossip" about transactions to create directed acyclic graphs that time-sequence transactions. Each "gossip" message contains one or more transactions plus a timestamp, a digital signature, and cryptographic hashes of two earlier events. This makes Hashgraph form an asynchronous Byzantine Fault-Tolerant (aBFT) consensus algorithm. Hashgraph w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Chain
A hash chain is the successive application of a cryptographic hash function to a piece of data. In computer security, a hash chain is a method to produce many one-time keys from a single key or password. For non-repudiation a hash function can be applied successively to additional pieces of data in order to record the chronology of data's existence. Definition A hash chain is a successive application of a cryptographic hash function h to a string x. For example, h(h(h(h(x)))) gives a hash chain of length 4, often denoted h^(x) Applications Leslie LamportL. Lamport, “Password Authentication with Insecure Communication”, Communications of the ACM 24.11 (November 1981), pp 770-772/ref> suggested the use of hash chains as a password protection scheme in an insecure environment. A server which needs to provide authentication may store a hash chain rather than a plain text password and prevent theft of the password in transmission or theft from the server. For example, a se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
