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A universal hashing scheme is a randomized algorithm that selects a hash function h among a family of such functions, in such a way that the probability of a collision of any two distinct keys is 1/m, where m is the number of distinct hash values desired—independently of the two keys. Universal hashing ensures (in a probabilistic sense) that ...
For instance, a function returning the start of a string can provide a hash appropriate for some applications but will never be a suitable checksum. Checksums are used as cryptographic primitives in larger authentication algorithms. For cryptographic systems with these two specific design goals [clarification needed], see HMAC.
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
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. A map implemented by a hash table is called a hash map.
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.
A hash function must be able to process an arbitrary-length message into a fixed-length output. This can be achieved by breaking the input up into a series of equally sized blocks, and operating on them in sequence using a one-way compression function. The compression function can either be specially designed for hashing or be built from a ...
In a CAS system, the directory does not map filenames onto locations, but uses the keys instead. [2] This provides several benefits. For one, when a file is sent to the CAS for storage, the hash function will produce a key and then check to see if that key already exists in the directory.
Binary hash chains are commonly used in association with a hash tree. A binary hash chain takes two hash values as inputs, concatenates them and applies a hash function to the result, thereby producing a third hash value. The above diagram shows a hash tree consisting of eight leaf nodes and the hash chain for the third leaf node.