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Hash functions are used in conjunction with hash tables to store and retrieve data items or data records. The hash function translates the key associated with each datum or record into a hash code, which is used to index the hash table. When an item is to be added to the table, the hash code may index an empty slot (also called a bucket), in ...
A cryptographic hash function (CHF) is a hash algorithm (a map of an arbitrary binary string to a binary string with a fixed size of bits) that has special properties desirable for a cryptographic application: [ 1 ] the probability of a particular n {\displaystyle n} -bit output result (hash value) for a random input string ("message") is 2 − ...
A minimal perfect hash function is a perfect hash function that maps n keys to n consecutive integers – usually the numbers from 0 to n − 1 or from 1 to n. A more formal way of expressing this is: Let j and k be elements of some finite set S. Then h is a minimal perfect hash function if and only if h(j) = h(k) implies j = k (injectivity ...
In computing, a hash table is a data structure that implements an associative array, also called a dictionary or simply map; an associative array is an abstract data type that maps keys to values. [ 2 ] 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 ...
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. [ 3 ][ 4 ] They are built using the Merkle–Damgård construction, from a one-way compression function itself built using the Davies–Meyer structure from a specialized block cipher.
In certain cryptographic hash functions such as RIPEMD-160, the former is less than the latter because RIPEMD-160 use two sets of parallel computation values and then combine into a single set of chaining values. ^ The maximum input size = 2length size − 1 bits. For example, the maximum input size of SHA-1 = 264 − 1 bits.
The MD5 message-digest algorithm is a widely used hash function producing a 128- bit hash value. MD5 was designed by Ronald Rivest in 1991 to replace an earlier hash function MD4, [3] and was specified in 1992 as RFC 1321. MD5 can be used as a checksum to verify data integrity against unintentional corruption. Historically it was widely used as ...
Consistent hashing. In computer science, consistent hashing 1 2 is a special kind of hashing technique such that when a hash table is resized, only keys need to be remapped on average where is the number of keys and is the number of slots. In contrast, in most traditional hash tables, a change in the number of array slots causes nearly all keys ...