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Hash function

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880:: whenever a single input bit is complemented, each of the output bits changes with a 50% probability. The reason for this property is that selected subsets of the keyspace may have low variability. For the output to be uniformly distributed, a low amount of variability, even one bit, should translate into a high amount of variability (i.e. distribution over the tablespace) in the output. Each bit should change with a probability of 50% because, if some bits are reluctant to change, then the keys become clustered around those values. If the bits want to change too readily, then the mapping is approaching a fixed XOR function of a single bit. Standard tests for this property have been described in the literature. The relevance of the criterion to a multiplicative hash function is assessed here. 2528:
initialized at the start of the program. The random numbers could be any length, but 64 bits was natural due to the 64 squares on the board. A position was transcribed by cycling through the pieces in a position, indexing the corresponding random numbers (vacant spaces were not included in the calculation) and XORing them together (the starting value could be 0 (the identity value for XOR) or a random seed). The resulting value was reduced by modulo, folding, or some other operation to produce a hash table index. The original Zobrist hash was stored in the table as the representation of the position.
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addition is also a plausible alternative. The final operation would be a modulo, mask, or other function to reduce the word value to an index the size of the table. The weakness of this procedure is that information may cluster in the upper or lower bits of the bytes; this clustering will remain in the hashed result and cause more collisions than a proper randomizing hash. ASCII byte codes, for example, have an upper bit of 0, and printable strings do not use the first 32 byte codes, so the information (95 bytecodes) is clustered in the remaining bits in an unobvious manner.
154: 908:) by a constant can be inverted to become a multiplication by the word-size multiplicative-inverse of that constant. This can be done by the programmer, or by the compiler. Division can also be reduced directly into a series of shift-subtracts and shift-adds, though minimizing the number of such operations required is a daunting problem; the number of assembly instructions resulting may be more than a dozen and swamp the pipeline. If the architecture has 493: 57: 889:
indexable by the key-value would be very large and very sparse, but very fast. A hash function takes a finite amount of time to map a potentially large keyspace to a feasible amount of storage space searchable in a bounded amount of time regardless of the number of keys. In most applications, the hash function should be computable with minimum latency and secondarily in a minimum number of instructions.
1556:) and can be 10 times slower than multiplication. A second drawback is that it will not break up clustered keys. For example, the keys 123000, 456000, 789000, etc. modulo 1000 all map to the same address. This technique works well in practice because many key sets are sufficiently random already, and the probability that a key set will be cyclical by a large prime number is small. 2743:
example, a 128-bit word will hash only a 26-character alphabetic string (ignoring case) with a radix of 29; a printable ASCII string is limited to 9 characters using radix 97 and a 64-bit word. However, alphabetic keys are usually of modest length, because keys must be stored in the hash table. Numeric character strings are usually not a problem; 64 bits can count up to
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the item is added to the table there. If the hash code indexes a full slot, then some kind of collision resolution is required: the new item may be omitted (not added to the table), or replace the old item, or be added to the table in some other location by a specified procedure. That procedure depends on the structure of the hash table. In
1513:, so the hash code is taken as the middle 4 digits of the 17-digit number (ignoring the high digit) 8750. The mid-squares method produces a reasonable hash code if there is not a lot of leading or trailing zeros in the key. This is a variant of multiplicative hashing, but not as good because an arbitrary key is not a good multiplier. 4031:
implementation of the service and present solutions for avoiding single points of failure and guaranteeing a service with reasonable and stable delay. Guardtime AS has been operating a KSI Infrastructure for 5 years. We summarize how the KSI Infrastructure is built, and the lessons learned during the operational period of the service.
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operations (e.g. multiplication by constant and bit-shifting). The final word, which may have unoccupied byte positions, is filled with zeros or a specified randomizing value before being folded into the hash. The accumulated hash code is reduced by a final modulo or other operation to yield an index into the table.
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other pathologies in the key set. Such strategies may be effective as a custom hash function if the structure of the keys is such that either the middle, ends, or other fields are zero or some other invariant constant that does not differentiate the keys; then the invariant parts of the keys can be ignored.
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In a hash table, a hash function takes a key as an input, which is associated with a datum or record and used to identify it to the data storage and retrieval application. The keys may be fixed-length, like an integer, or variable-length, like a name. In some cases, the key is the datum itself. The
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Worst case results for a hash function can be assessed two ways: theoretical and practical. The theoretical worst case is the probability that all keys map to a single slot. The practical worst case is the expected longest probe sequence (hash function + collision resolution method). This analysis
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The paradigmatic example of folding by characters is to add up the integer values of all the characters in the string. A better idea is to multiply the hash total by a constant, typically a sizable prime number, before adding in the next character, ignoring overflow. Using exclusive-or instead of
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A hash function can be designed to exploit existing entropy in the keys. If the keys have leading or trailing zeros, or particular fields that are unused, always zero or some other constant, or generally vary little, then masking out only the volatile bits and hashing on those will provide a better
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In some applications, the input data may contain features that are irrelevant for comparison purposes. For example, when looking up a personal name, it may be desirable to ignore the distinction between upper and lower case letters. For such data, one must use a hash function that is compatible with
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Later, the method was extended to hashing integers by representing each byte in each of 4 possible positions in the word by a unique 32-bit random number. Thus, a table of 2×4 random numbers is constructed. A 32-bit hashed integer is transcribed by successively indexing the table with the value of
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Multiplicative hashing is susceptible to a "common mistake" that leads to poor diffusion—higher-value input bits do not affect lower-value output bits. A transmutation on the input which shifts the span of retained top bits down and XORs or ADDs them to the key before the multiplication step
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In data storage and retrieval applications, the use of a hash function is a trade-off between search time and data storage space. If search time were unbounded, then a very compact unordered linear list would be the best medium; if storage space were unbounded, then a randomly accessible structure
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function of the number of keys to be mapped versus the number of table slots that they are mapped into. Finding a perfect hash function over more than a very small set of keys is usually computationally infeasible; the resulting function is likely to be more computationally complex than a standard
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Hash tables often contain only a small subset of the valid inputs. For instance, a club membership list may contain only a hundred or so member names, out of the very large set of all possible names. In these cases, the uniformity criterion should hold for almost all typical subsets of entries that
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is usually a prime number large enough to hold the number of different characters in the character set of potential keys. Radix conversion hashing of strings minimizes the number of collisions. Available data sizes may restrict the maximum length of string that can be hashed with this method. For
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characters of a string along with the length, or form a word-size hash from the middle 4 characters of a string. This saves iterating over the (potentially long) string, but hash functions that do not hash on all characters of a string can readily become linear due to redundancies, clustering, or
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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 which case
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If the keys are uniformly or sufficiently uniformly distributed over the key space, so that the key values are essentially random, then they may be considered to be already "hashed". In this case, any number of any bits in the key may be extracted and collated as an index into the hash table. For
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It is often desirable that the output of a hash function have fixed size (but see below). If, for example, the output is constrained to 32-bit integer values, then the hash values can be used to index into an array. Such hashing is commonly used to accelerate data searches. Producing fixed-length
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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.
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Zobrist hashing was originally introduced as a means of compactly representing chess positions in computer game-playing programs. A unique random number was assigned to represent each type of piece (six each for black and white) on each space of the board. Thus a table of 64×12 such numbers is
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key sets, and poorly designed hash functions can result in access times approaching linear in the number of items in the table. Hash functions can be designed to give the best worst-case performance, good performance under high table loading factors, and in special cases, perfect (collisionless)
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Modern microprocessors will allow for much faster processing if 8-bit character strings are not hashed by processing one character at a time, but by interpreting the string as an array of 32-bit or 64-bit integers and hashing/accumulating these "wide word" integer values by means of arithmetic
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is the table size, and using a parity-preserving bitwise operation such as ADD or XOR to combine the sections, followed by a mask or shifts to trim off any excess bits at the high or low end. For example, for a table size of 15 bits and a 64-bit key value of 0x0123456789ABCDEF, there are five
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If keys are being hashed repeatedly, and the hash function is costly, then computing time can be saved by precomputing the hash codes and storing them with the keys. Matching hash codes almost certainly means that the keys are identical. This technique is used for the transposition table in
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Keyless Signatures Infrastructure (KSI) is a globally distributed system for providing time-stamping and server-supported digital signature services. Global per-second hash trees are created and their root hash values published. We discuss some service quality issues that arise in practical
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is the number of distinct hash values desired—independently of the two keys. Universal hashing ensures (in a probabilistic sense) that the hash function application will behave as well as if it were using a random function, for any distribution of the input data. It will, however, have more
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output from variable-length input can be accomplished by breaking the input data into chunks of specific size. Hash functions used for data searches use some arithmetic expression that iteratively processes chunks of the input (such as the characters in a string) to produce the hash value.
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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.
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Computational complexity varies with the number of instructions required and latency of individual instructions, with the simplest being the bitwise methods (folding), followed by the multiplicative methods, and the most complex (slowest) are the division-based methods.
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In many applications, the range of hash values may be different for each run of the program or may change along the same run (for instance, when a hash table needs to be expanded). In those situations, one needs a hash function which takes two parameters—the input data
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mapping of keys into hash codes. Implementation is based on parity-preserving bit operations (XOR and ADD), multiply, or divide. A necessary adjunct to the hash function is a collision-resolution method that employs an auxiliary data structure like
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is a 7-bit character encoding, although it is often stored in 8-bit bytes with the highest-order bit always clear (zero). Therefore, for plain ASCII, the bytes have only 2 = 128 valid values, and the character translation table has only this many
2524:, is a method for constructing universal families of hash functions by combining table lookup with XOR operations. This algorithm has proven to be very fast and of high quality for hashing purposes (especially hashing of integer-number keys). 602:—pairs of inputs that are mapped to the same hash value—increases. If some hash values are more likely to occur than others, then a larger fraction of the lookup operations will have to search through a larger set of colliding table entries. 2532:
each byte of the plain text integer and XORing the loaded values together (again, the starting value can be the identity value or a random seed). The natural extension to 64-bit integers is by use of a table of 2×8 64-bit random numbers.
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until an open slot is located or the entire table is probed (overflow). Searching for the item follows the same procedure until the item is located, an open slot is found, or the entire table has been searched (item not in table).
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offers a natural analogy with its non-technical meaning (to chop up or make a mess out of something), given how hash functions scramble their input data to derive their output. In his research for the precise origin of the term,
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pHash is an open source software library released under the GPLv3 license that implements several perceptual hashing algorithms, and provides a C-like API to use those functions in your own programs. pHash itself is written in
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of consecutive keys with respect to any block of bits in the key. Consecutive keys within the high bits or low bits of the key (or some other field) are relatively common. The multipliers for various word lengths are:
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Because collisions should be infrequent, and cause a marginal delay but are otherwise harmless, it is usually preferable to choose a faster hash function over one that needs more computation but saves a few collisions.
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or the time of day. It also excludes functions that depend on the memory address of the object being hashed, because the address may change during execution (as may happen on systems that use certain methods of
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criterion being used: that is, any two inputs that are considered equivalent must yield the same hash value. This can be accomplished by normalizing the input before hashing it, as by upper-casing all letters.
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When the hash function is used to store values in a hash table that outlives the run of the program, and the hash table needs to be expanded or shrunk, the hash table is referred to as a dynamic hash table.
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There are several common algorithms for hashing integers. The method giving the best distribution is data-dependent. One of the simplest and most common methods in practice is the modulo division method.
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for large data sets stored in slow media. A cache is generally simpler than a hashed search table, since any collision can be resolved by discarding or writing back the older of the two colliding items.
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and possibly faster hash function. Selected divisors or multipliers in the division and multiplicative schemes may make more uniform hash functions if the keys are cyclic or have other redundancies.
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appears to have been the first to use the concept of a hash function in a memo dated January 1953, the term itself did not appear in published literature until the late 1960s, in Herbert Hellerman's
253:. Although the concepts overlap to some extent, each one has its own uses and requirements and is designed and optimized differently. The hash function differs from these concepts mainly in terms of 671:
In special cases when the keys are known in advance and the key set is static, a hash function can be found that achieves absolute (or collisionless) uniformity. Such a hash function is said to be
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Use of hash functions relies on statistical properties of key and function interaction: worst-case behavior is intolerably bad but rare, and average-case behavior can be nearly optimal (minimal
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to compute the hash function, and it becomes a function of the previous keys that have been inserted. Several algorithms that preserve the uniformity property but require time proportional to
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A good hash function should map the expected inputs as evenly as possible over its output range. That is, every hash value in the output range should be generated with roughly the same
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back into the low byte of the cumulative quantity. The result is a word-size hash code to which a modulo or other reducing operation can be applied to produce the final hash index.
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worries about adversarial attack on real time systems, Gonnet has shown that the probability of such a case is "ridiculously small". His representation was that the probability of
1552:. This gives good results over a large number of key sets. A significant drawback of division hashing is that division is microprogrammed on most modern architectures (including 1023:
A hash function that allows only certain table sizes or strings only up to a certain length, or cannot accept a seed (i.e. allow double hashing) is less useful than one that does.
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Buldas, Ahto; Kroonmaa, Andres; Laanoja, Risto (2013). "Keyless Signatures' Infrastructure: How to Build Global Distributed Hash-Trees". In Riis, Nielson H.; Gollmann, D. (eds.).
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adds the feature that hash functions make use of a randomized seed that is generated once when the Python process starts in addition to the input to be hashed. The Python hash (
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entries), etc. Invalid data values (such as the country code "xx" or the ZIP code 00000) may be left undefined in the table or mapped to some appropriate "null" value.
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in any sense. A good randomizing function is (barring computational efficiency concerns) generally a good choice as a hash function, but the converse need not be true.
698:. This test is a goodness-of-fit measure: it is the actual distribution of items in buckets versus the expected (or uniform) distribution of items. The formula is 1039:: Minor input changes result in a random-looking output alteration, known as the diffusion property. Thus, hash functions are valuable for key derivation functions. 177:
of arbitrary size to fixed-size values, though there are some hash functions that support variable-length output. The values returned by a hash function are called
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Password storage: The password's hash value does not expose any password details, emphasizing the importance of securely storing hashed passwords on the server.
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of the data to be hashed, in the mathematical sense of the term. This requirement excludes hash functions that depend on external variable parameters, such as
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If the data to be hashed is small enough, then one can use the data itself (reinterpreted as an integer) as the hashed value. The cost of computing this
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A mid-squares hash code is produced by squaring the input and extracting an appropriate number of middle digits or bits. For example, if the input is
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to not be a power of 2 and still not have to perform any remainder or division operation, as these computations are sometimes costly. For example, let
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hash function and provides only a marginal advantage over a function with good statistical properties that yields a minimum number of collisions. See
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are examples of dynamic hash functions that execute in constant time but relax the property of uniformity to achieve the minimal movement property.
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A ratio within one confidence interval (such as 0.95 to 1.05) is indicative that the hash function evaluated has an expected uniform distribution.
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of a small change in input value creating a drastic change in output value. Perceptual hash functions are widely used in finding cases of online
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Hash functions can have some technical properties that make it more likely that they will have a uniform distribution when applied. One is the
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will get large, or both, for the scheme to be computationally feasible. Therefore, it is more suited to hardware or microcode implementation.
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character string representing a decimal number is converted to a numeric quantity for computing, a variable-length string can be converted as
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A good hash function satisfies two basic properties: it should be very fast to compute, and it should minimize duplication of output values (
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A hash function that will relocate the minimum number of records when the table is resized is desirable. What is needed is a hash function
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Algebraic coding is a variant of the division method of hashing which uses division by a polynomial modulo 2 instead of an integer to map
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Today, especially with the advent of 64-bit word sizes, much more efficient variable-length string hashing by word chunks is available.
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Wagner, Urs; Lugrin, Thomas (2023), Mulder, Valentin; Mermoud, Alain; Lenders, Vincent; Tellenbach, Bernhard (eds.), "Hash Functions",
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this translates into a single integer multiplication and right-shift, making it one of the fastest hash functions to compute.
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is done by default in low-level programming languages and integer division by a power of 2 is simply a right-shift, so, in
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A hash function is applicable in a variety of situations. Particularly within cryptography, notable applications include:
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because of the ability to have a correlation between hashes so similar data can be found (for instance with a differing
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that may occur in the application. Depending on the function, the remainder may be uniform only for certain values of
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Castro, Julio Cesar Hernandez; et al. (3 February 2005). "The strict avalanche criterion randomness test".
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The meaning of "small enough" depends on the size of the type that is used as the hashed value. For example, in
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among a family of such functions, in such a way that the probability of a collision of any two distinct keys is
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This is useful in cases where keys are devised by a malicious agent, for example in pursuit of a DOS attack.
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in the 1970s, was originally designed for hashing identifiers into compiler symbol tables as given in the
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When testing a hash function, the uniformity of the distribution of hash values can be evaluated by the
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This article is about a computer programming construct. For other meanings of "hash" and "hashing", see
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sections consisting of 0x4DEF, 0x1357, 0x159E, 0x091A, and 0x0. Adding yields 0x7FFE, a 15-bit value.
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collisions than perfect hashing and may require more operations than a special-purpose hash function.
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output is a hash code used to index a hash table holding the data or records, or pointers to them.
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for their effectiveness, reducing access time to nearly constant. High table loading factors,
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The multiplier should be odd, so the least significant bit of the output is invertible modulo
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considers uniform hashing, that is, any key will map to any particular slot with probability
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Scramble the bits of the key so that the resulting values are uniformly distributed over the
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game-playing programs, which stores a 64-bit hashed representation of the board position.
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unsigned hash(unsigned K) { K ^= K >> (w-m); return (a*K) >> (w-m); }
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modulo 2. If follows that the corresponding hash function will map keys with fewer than
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Proceedings of the Eighth ACM Conference on Data and Application Security and Privacy
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A standard technique is to use a modulo function on the key, by selecting a divisor
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A common solution is to compute a fixed hash function with a very large range (say,
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Division-based implementations can be of particular concern because the division is
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This kind of function has some nice theoretical properties, one of which is called
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least significant bits and use the result as an index into a hash table of size
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Other types of data can also use this hashing scheme. For example, when mapping
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may be found in the table, not just for the global set of all possible entries.
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that is uniform on the interval . A hash function uniform on the interval is
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The determinism is in the context of the reuse of the function. For example,
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Unique permutation hashing has a guaranteed best worst-case insertion time.
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Map the key values into ones less than or equal to the size of the table.
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hashing is a form of multiplicative hashing in which the multiplier is
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A folding hash code is produced by dividing the input into sections of
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table slots, then the probability of a bucket receiving many more than
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objects can simply use the value directly, whereas the 64-bit integer
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are used in cybersecurity to secure sensitive data such as passwords.
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Hash Function Construction for Textual and Geometrical Data Retrieval
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Menezes, Alfred J.; van Oorschot, Paul C.; Vanstone, Scott A (1996).
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like "us" or "za" to country names (26 = 676 table entries), 5-digit
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A hash function that maps names to integers from 0 to 15. There is a
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Expected Length of the Longest Probe Sequence in Hash Code Searching
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Pagani, Fabio; Dell'Amico, Matteo; Balzarotti, Davide (2018-03-13).
492: 197:. The values are usually used to index a fixed-size table called a 56: 4045:"pHash.org: Home of pHash, the open source perceptual hash library" 3454: 1425: 31: 2929:, but not exactly the same, as other data. This is in contrast to 2902:="AAA"). The hash function used for the algorithm is usually the 4358: 1784:
or fewer non-zero coefficients, then keys which share fewer than
1404: 1286:
uses a dynamic hash function that requires space proportional to
1092: 418:. The table is often an array with two or more indices (called a 37:"Hash code" redirects here. For the programming competition, see 460:
in a set of points, similar shapes in a list of shapes, similar
3409: 2650: 2293:
unsigned hash(unsigned K) { return (a*K) >> (w-m); }
406:. In these applications, the set of all inputs is some sort of 250: 4121:
The Art of Computer Programming, Vol. 3, Sorting and Searching
4077:
The Art of Computer Programming, Vol. 3, Sorting and Searching
3865:
Sarantinos, Nikolaos; Benzaïd, Chafika; Arabiat, Omar (2016).
3817: 3356:
The Art of Computer Programming, Vol. 3, Sorting and Searching
1316:
A hash function with minimal movement is especially useful in
277:
A hash function may be considered to perform three functions:
3774: 3154: 2693: 1368:, the hash code is a 32-bit integer. Thus the 32-bit integer 433: 432:, and similar names), and the hash function returns an index 30:"hashlink" redirects here. For the Haxe virtual machine, see 2821:
separately, requires a number of operations proportional to
1199:
Variable range with minimal movement (dynamic hash function)
915:, then the multiply-by-inverse is likely a better approach. 320:, or systematic probing of the table to find an empty slot. 4287: 3991: 3489:"Fibonacci Hashing: The Optimization that the World Forgot" 3444: 3415: 1046: 955:. We can replace the division by a (possibly faster) right 4036: 3261:
Knuth conveniently leaves the proof of this to the reader.
1058:: Message hashes are signed rather than the whole message. 3960:
2013 Fourth Cybercrime and Trustworthy Computing Workshop
3082: 2561: 1553: 1357:
hash function is effectively zero. This hash function is
1084:), although sometimes rehashing of the item is possible. 203:. Use of a hash function to index a hash table is called 4044: 3864: 3089:, even though it was already widespread jargon by then. 1684:. The remainder using polynomial arithmetic modulo 2 is 281:
Convert variable-length keys into fixed-length (usually
225:
Hash functions are related to (and often confused with)
2925:, also known as similarity hashing, is a technique for 642:
records should be vanishingly small. In particular, if
3645:
A New Hashing Method with Application for Game Playing
2977:
of the multimedia are similar. This is in contrast to
2308:
corrects for this. The resulting function looks like:
1403:), the table has only 2 = 256 entries; in the case of 3997: 3951:
Oliver, Jonathan; Cheng, Chun; Chen, Yanggui (2013).
3705:"Performance in Practice of String Hashing Functions" 3592:
Dolev, Shlomi; Lahiani, Limor; Haviv, Yinnon (2013).
3562: 3560: 3510:, Cham: Springer Nature Switzerland, pp. 21–24, 3508:
Trends in Data Protection and Encryption Technologies
3173: 2584:
Simplistic hash functions may add the first and last
1922: 706: 3908: 1525:
which is a prime number close to the table size, so
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Hash_RC6 — Variable length Hash algorithm using RC6
3291:Aggarwal, Kirti; Verma, Harsh K. (March 19, 2015). 2556:When the data values are long (or variable-length) 1979:{\displaystyle P(x)=\prod _{j\in S}(x-\alpha ^{j})} 1444:example, a simple hash function might mask off the 410:, and the hashing function can be interpreted as a 81:. Unsourced material may be challenged and removed. 4203: 3944: 3557: 3417: 3245: 1978: 1361:, as it maps each input to a distinct hash value. 837: 376:Hash functions are an essential ingredient of the 3591: 2793:-character string by advancing a window of width 2174:Standard multiplicative hashing uses the formula 4434: 3702: 3477: 3014:, a characteristic of universal hash functions. 2730:as the characters of the input string of length 2225:is an appropriately chosen value that should be 2117:is any nonzero polynomial modulo 2 with at most 2001:are computed in this field. Then the degree of 1234:is the number of allowed hash values) such that 307:). Hash functions rely on generating favorable 3950: 2853:is the number of occurrences of the substring. 2551: 3709:Database Systems for Advanced Applications '97 3662: 4189: 4111: 4109: 3290: 2282:. This is special because arithmetic modulo 2161: 1337: 904:on nearly all chip architectures. Division ( 605:This criterion only requires the value to be 3829:. New York, NY, USA: ACM. pp. 354–365. 3541:"3. Data model — Python 3.6.1 documentation" 3505: 3346: 3344: 3342: 3340: 3240: 3180: 2856:The most familiar algorithm of this type is 2516:Tabulation hashing, more generally known as 2037:is a root, it follows that the coefficients 444:, and many other disciplines, to solve many 334:Hash functions are used in conjunction with 3676:Compilers: Principles, Techniques and Tools 3393:"Understanding CPU caching and performance" 3246:{\displaystyle S=\{1,2,3,4,5,6,8,10,12,9\}} 2644: 2542: 161:between keys "John Smith" and "Sandra Dee". 27:Mapping arbitrary data to fixed-size values 4196: 4182: 4106: 3780: 3703:Ramakrishna, M. V.; Zobel, Justin (1997). 1879:be the smallest set of integers such that 1407:characters, the table would have 17 × 2 = 689: 3928: 3923:. 3, Supplement (September 2006): 91–97. 3716: 3609: 3567:Sedgewick, Robert (2002). "14. Hashing". 3566: 3515: 3337: 2169: 1346: 577:Learn how and when to remove this message 141:Learn how and when to remove this message 3914: 3486: 2937:and detecting multiple versions of code. 2636:Universal hashing § Hashing strings 2568:has highly non-uniform distributions of 1438: 152: 3638: 3447:Mathematics and Computers in Simulation 2860:with best and average case performance 471:Hash tables are also used to implement 398:A special case of hashing is known as 14: 4435: 4093: 3390: 2747:, or 19 decimal digits with radix 10. 2629: 1420:The same technique can be used to map 368:Hash functions are also used to build 4177: 4115: 4098:(Technical report). Ontario, Canada: 4071: 4042: 3350: 2831:. However, with the proper choice of 2290:, for example, this function becomes 2255:. In this case, this formula becomes 1323: 4043:Klinger, Evan; Starkweather, David. 3626:"CS 3110 Lecture 21: Hash functions" 2799:characters along the string, where 2594: 2314: 1788:bits are guaranteed to not collide. 620:In other words, if a typical set of 515:adding citations to reliable sources 486: 436:. This principle is widely used in 79:adding citations to reliable sources 50: 3953:"TLSH -- A Locality Sensitive Hash" 3628:. Section "Multiplicative hashing". 2961:that produces a snippet, hash, or 2692:. This is simply a polynomial in a 1806:(the last of which is a divisor of 1559: 1516: 363: 39:Hash Code (programming competition) 24: 3783:"NIST Special Publication 800-168" 3087:Digital Computer System Principles 2941: 2771:, one can compute a hash function 2579: 2501: 2147:bits in common to unique indices. 1644:can be regarded as the polynomial 25: 4459: 4141: 3872:2016 IEEE Trustcom/BigDataSE/ISPA 3763: 3711:. DASFAA 1997. pp. 215–224. 3167:For example, for n=15, k=4, t=6, 3033:keys mapping to a single slot is 2969:. A perceptual hash is a type of 2649:Analogous to the way an ASCII or 2603:The classic approach, dubbed the 2213:, which produces a hash value in 2150:The usual outcome is that either 1494:, then squaring the key produces 1107: 866:is the number of items in bucket 3487:Sharupke, Malte (16 June 2018). 3420:Handbook of Applied Cryptography 2947:This section is an excerpt from 2915:This section is an excerpt from 1872:. The derivation is as follows: 1098: 1062: 1018: 491: 387:that is used to test whether an 259:non-cryptographic hash functions 55: 4148:Calculate hash of a given value 4087: 4065: 4000:Secure IT Systems. NordSec 2013 3757: 3696: 3656: 3632: 3618: 3585: 3533: 3358:. Reading, MA., United States: 3264: 3255: 3161: 3147: 2750: 2330:is the machine word length and 1077:pseudo-random number generators 976: 502:needs additional citations for 66:needs additional citations for 3781:Breitinger, Frank (May 2014). 3571:(3 ed.). Addison Wesley. 3499: 3438: 3384: 3316: 3284: 3138: 2927:detecting data that is similar 2767:In some applications, such as 1990:and where the coefficients of 1973: 1954: 1932: 1926: 1810:) and is constructed from the 1472: 855:is the number of buckets, and 826: 805: 802: 785: 772: 753: 750: 737: 323: 13: 1: 4154:The Goulburn Hashing Function 3904:. 10.1109/TrustCom.2016.0274. 3820:"Beyond Precision and Recall" 3324:"NIST Glossary — hash digest" 3277: 2909: 2763:Linear congruential generator 2077:, so they are all 0 or 1. If 995:that selects a hash function 936:pseudorandom number generator 883: 589: 482: 414:of that space into a grid of 4008:10.1007/978-3-642-41488-6_21 3598:Theoretical Computer Science 3594:"Unique permutation hashing" 3463:10.1016/j.matcom.2004.09.001 2931:cryptographic hash functions 2552:Hashing variable-length data 1228:is the key being hashed and 1043:Message Authentication Codes 918:We can allow the table size 263:cryptographic hash functions 7: 3517:10.1007/978-3-031-33386-6_5 3303:10.1109/ICACEA.2015.7164747 3092: 3001: 2121:nonzero coefficients, then 930:be significantly less than 268: 10: 4464: 3930:10.1016/j.diin.2006.06.015 3884:10.1109/TrustCom.2016.0274 3727:10.1142/9789812819536_0023 3391:Stokes, Jon (2002-07-08). 3063: 2946: 2914: 2760: 2754: 2702:that takes the components 2633: 2505: 2162:Unique permutation hashing 1455: 1428:like 13083 to city names ( 1380:and 64-bit floating-point 1372:and 32-bit floating-point 1338:Hashing integer data types 1261:with probability close to 980: 878:strict avalanche criterion 327: 287:parity-preserving operator 209:scatter-storage addressing 43: 36: 29: 4412: 4296: 4215: 3611:10.1016/j.tcs.2012.12.047 2560:—such as personal names, 1821:gives an example: taking 1142:, and use the division's 1067:A hash procedure must be 309:probability distributions 3915:Kornblum, Jesse (2006). 3767:A Handbook of Algorithms 3131: 3120:Low-discrepancy sequence 2973:, which is analogous if 2959:fingerprinting algorithm 2805:is a fixed integer, and 2645:Radix conversion hashing 2543:Customized hash function 1572:bits. In this approach, 1487:and the hash table size 1422:two-letter country codes 1298:to compute the value of 1136:), divide the result by 1125:of allowed hash values. 173:that can be used to map 4417:List of data structures 3962:. IEEE. pp. 7–13. 3835:10.1145/3176258.3176306 3798:10.6028/NIST.SP.800-168 3105:Nearest neighbor search 2971:locality-sensitive hash 1780:is constructed to have 1318:distributed hash tables 851:is the number of keys, 690:Testing and measurement 684:universal hash function 454:three-dimensional space 243:randomization functions 4100:University of Waterloo 3878:. pp. 1782–1787. 3247: 3110:Distributed hash table 3100:List of hash functions 2987:copyright infringement 2981:, which relies on the 2170:Multiplicative hashing 1980: 1579:, and we postulate an 1347:Identity hash function 1156:, this can be done by 839: 736: 442:computational geometry 257:. Hash tables may use 247:error-correcting codes 162: 3921:Digital Investigation 3270:Unisys large systems. 3248: 2979:cryptographic hashing 2607:based on the work of 2132:is not a multiple of 1981: 1583:th-degree polynomial 1439:Trivial hash function 1152:is itself a power of 840: 710: 626:records is hashed to 607:uniformly distributed 156: 46:Hash (disambiguation) 4314:Breadth-first search 3171: 3050:is the load factor, 2965:of various forms of 2935:data loss prevention 2896:="AAAAAAAAAAA", and 2537:3-tuple independence 2247:are powers of 2 and 1988:α ∈ GF(2) 1920: 1393:upper and lower case 1313:have been invented. 993:randomized algorithm 704: 658:is much larger than 511:improve this article 380:, a space-efficient 345:open address hashing 75:improve this article 4404:Topological sorting 4334:Dynamic programming 4094:Gonnet, G. (1978). 3368:1973acp..book.....K 3125:Transposition table 2630:Word length folding 2609:Peter J. Weinberger 2154:will get large, or 1175:, for any value of 4422:List of algorithms 4329:Divide and conquer 4324:Depth-first search 4319:Brute-force search 4233:Binary search tree 3968:10.1109/ctc.2013.9 3640:Zobrist, Albert L. 3569:Algorithms in Java 3243: 3077:notes that, while 2955:Perceptual hashing 2949:Perceptual hashing 2562:web page addresses 2508:Tabulation hashing 1976: 1953: 1606:+ ⋯ + ζ 1324:Data normalization 1284:Extendible hashing 1247: + 1) = 1082:garbage collection 1031:Integrity checking 835: 473:associative arrays 456:, such as finding 446:proximity problems 163: 4448:Search algorithms 4430: 4429: 4228:Associative array 4130:978-0-201-89685-5 4017:978-3-642-41487-9 3977:978-1-4799-3076-0 3893:978-1-5090-3205-1 3790:NIST Publications 3527:978-3-031-33386-6 3377:978-0-201-03803-3 2991:digital forensics 2904:Rabin fingerprint 2700: > 1 2595:Character folding 2558:character strings 2315:Fibonacci hashing 1938: 1794:is a function of 1389:character strings 1119:, and the number 989:universal hashing 983:Universal hashing 910:hardware multiply 830: 587: 586: 579: 561: 438:computer graphics 400:geometric hashing 391:is a member of a 353:quadratic probing 239:lossy compression 151: 150: 143: 125: 16:(Redirected from 4455: 4399:String-searching 4198: 4191: 4184: 4175: 4174: 4160:) by Mayur Patel 4135: 4134: 4117:Knuth, Donald E. 4113: 4104: 4103: 4091: 4085: 4084: 4073:Knuth, Donald E. 4069: 4063: 4062: 4056: 4055: 4040: 4034: 4033: 3995: 3989: 3988: 3986: 3984: 3957: 3948: 3942: 3941: 3939: 3937: 3932: 3912: 3906: 3905: 3877: 3862: 3856: 3855: 3853: 3851: 3824: 3815: 3809: 3808: 3806: 3804: 3787: 3778: 3772: 3771: 3761: 3755: 3754: 3752: 3751: 3720: 3700: 3694: 3693: 3660: 3654: 3652: 3650: 3636: 3630: 3629: 3622: 3616: 3615: 3613: 3589: 3583: 3582: 3564: 3555: 3554: 3552: 3551: 3537: 3531: 3530: 3519: 3503: 3497: 3496: 3484: 3475: 3474: 3442: 3436: 3435: 3423: 3413: 3407: 3406: 3404: 3403: 3388: 3382: 3381: 3352:Knuth, Donald E. 3348: 3335: 3334: 3332: 3330: 3320: 3314: 3313: 3311: 3309: 3288: 3271: 3268: 3262: 3259: 3253: 3252: 3250: 3249: 3244: 3165: 3159: 3151: 3145: 3142: 3059: 3049: 3043: 3032: 3026: 3013: 2983:avalanche effect 2957:is the use of a 2901: 2895: 2889: 2874: 2852: 2846: 2836: 2830: 2820: 2814: 2804: 2798: 2792: 2782: 2776: 2769:substring search 2746: 2741: 2735: 2729: 2701: 2691: 2589: 2566:natural language 2497: 2487: 2486: 2483: 2480: 2477: 2474: 2471: 2465: 2461: 2460: 2457: 2454: 2438: 2437: 2434: 2431: 2428: 2422: 2418: 2417: 2414: 2398: 2397: 2394: 2391: 2385: 2381: 2380: 2364: 2363: 2357: 2333: 2329: 2325: 2303: 2299: 2285: 2281: 2280: 2272: 2250: 2246: 2239: 2232: 2227:relatively prime 2224: 2220: 2212: 2211: 2191: 2157: 2153: 2146: 2142: 2131: 2120: 2116: 2076: 2068: 2067: 2053: 2042: 2036: 2032: 2021: 2017: 2015: 2000: 1989: 1985: 1983: 1982: 1977: 1972: 1971: 1952: 1912: 1889: 1878: 1871: 1836: 1816: 1809: 1805: 1801: 1797: 1793: 1787: 1783: 1779: 1768: 1731: 1683: 1643: 1610: 1582: 1578: 1571: 1567: 1560:Algebraic coding 1551: 1543: 1524: 1517:Division hashing 1512: 1511: 1508: 1505: 1502: 1499: 1493: 1492: 1486: 1485: 1482: 1467: 1463: 1451: 1447: 1434: 1433: 1416: 1415: 1412: 1383: 1379: 1375: 1371: 1312: 1297: 1291: 1271: 1260: 1233: 1227: 1221: 1186: 1180: 1174: 1167: 1155: 1151: 1141: 1135: 1131: 1124: 1118: 1013: 1007: 1000: 968: 954: 944: 933: 929: 923: 913:functional units 869: 865: 854: 850: 844: 842: 841: 836: 831: 829: 795: 783: 779: 765: 764: 749: 748: 735: 724: 708: 696:chi-squared test 666:birthday problem 663: 657: 651: 641: 631: 625: 582: 575: 571: 568: 562: 560: 519: 495: 487: 364:Specialized uses 289:like ADD or XOR, 146: 139: 135: 132: 126: 124: 83: 59: 51: 21: 4463: 4462: 4458: 4457: 4456: 4454: 4453: 4452: 4433: 4432: 4431: 4426: 4408: 4339:Graph traversal 4292: 4216:Data structures 4211: 4205:Data structures 4202: 4144: 4139: 4138: 4131: 4114: 4107: 4092: 4088: 4079:. Reading, MA: 4070: 4066: 4053: 4051: 4041: 4037: 4018: 3996: 3992: 3982: 3980: 3978: 3955: 3949: 3945: 3935: 3933: 3913: 3909: 3894: 3875: 3863: 3859: 3849: 3847: 3845: 3822: 3816: 3812: 3802: 3800: 3785: 3779: 3775: 3762: 3758: 3749: 3747: 3737: 3701: 3697: 3690: 3682:. p. 435. 3678:. Reading, MA: 3661: 3657: 3648: 3637: 3633: 3624: 3623: 3619: 3590: 3586: 3579: 3565: 3558: 3549: 3547: 3545:docs.python.org 3539: 3538: 3534: 3528: 3504: 3500: 3485: 3478: 3443: 3439: 3432: 3414: 3410: 3401: 3399: 3389: 3385: 3378: 3349: 3338: 3328: 3326: 3322: 3321: 3317: 3307: 3305: 3289: 3285: 3280: 3275: 3274: 3269: 3265: 3260: 3256: 3172: 3169: 3168: 3166: 3162: 3152: 3148: 3143: 3139: 3134: 3129: 3095: 3079:Hans Peter Luhn 3066: 3051: 3045: 3034: 3028: 3022: 3008: 3004: 2999: 2998: 2952: 2944: 2942:Perceptual hash 2939: 2938: 2920: 2912: 2897: 2891: 2876: 2875:and worst case 2861: 2848: 2838: 2832: 2822: 2816: 2806: 2800: 2794: 2788: 2778: 2772: 2765: 2759: 2753: 2744: 2737: 2731: 2727: 2717: 2710: 2703: 2696: 2690: 2680: 2673: 2663: 2654: 2647: 2638: 2632: 2597: 2585: 2582: 2580:Middle and ends 2574:character pairs 2554: 2545: 2518:Zobrist hashing 2514: 2512:Zobrist hashing 2506:Main articles: 2504: 2502:Zobrist hashing 2495: 2490: 2484: 2481: 2478: 2475: 2472: 2469: 2467: 2464: 2458: 2455: 2452: 2450: 2449: 2441: 2435: 2432: 2429: 2426: 2424: 2421: 2415: 2412: 2410: 2409: 2401: 2395: 2392: 2389: 2387: 2384: 2378: 2376: 2375: 2367: 2361: 2359: 2356: 2352: 2331: 2327: 2323: 2317: 2312: 2301: 2297: 2294: 2283: 2278: 2270: 2264: 2256: 2251:is the machine 2248: 2241: 2234: 2230: 2222: 2214: 2209: 2189: 2183: 2175: 2172: 2164: 2155: 2151: 2144: 2133: 2122: 2118: 2115: 2105: 2095: 2078: 2075: 2066: 2061: 2060: 2059: 2055: 2044: 2038: 2034: 2023: 2019: 2011: 2002: 1991: 1987: 1967: 1963: 1942: 1921: 1918: 1917: 1891: 1880: 1876: 1838: 1822: 1814: 1807: 1803: 1799: 1795: 1791: 1785: 1781: 1770: 1767: 1763: 1757: 1750: 1733: 1730: 1720: 1710: 1685: 1682: 1672: 1662: 1645: 1642: 1638: 1632: 1625: 1612: 1609: 1602: 1584: 1580: 1573: 1569: 1565: 1562: 1545: 1526: 1522: 1519: 1509: 1506: 1503: 1500: 1497: 1495: 1490: 1488: 1483: 1480: 1478: 1475: 1465: 1461: 1458: 1449: 1445: 1441: 1431: 1429: 1413: 1410: 1408: 1381: 1377: 1373: 1369: 1349: 1340: 1326: 1299: 1293: 1287: 1270: + 1) 1262: 1235: 1229: 1223: 1208: 1201: 1182: 1176: 1169: 1165: 1153: 1147: 1137: 1134:2 − 1 1133: 1129: 1120: 1114: 1110: 1101: 1065: 1021: 1009: 1002: 996: 985: 979: 964:(key) >> 960: 946: 939: 931: 925: 919: 902:microprogrammed 886: 867: 864: 856: 852: 848: 791: 784: 775: 760: 756: 744: 740: 725: 714: 709: 707: 705: 702: 701: 692: 659: 653: 643: 633: 627: 621: 592: 583: 572: 566: 563: 526:"Hash function" 520: 518: 508: 496: 485: 366: 341:chained hashing 332: 326: 271: 147: 136: 130: 127: 90:"Hash function" 84: 82: 72: 60: 49: 42: 35: 28: 23: 22: 15: 12: 11: 5: 4461: 4451: 4450: 4445: 4443:Hash functions 4428: 4427: 4425: 4424: 4419: 4413: 4410: 4409: 4407: 4406: 4401: 4396: 4391: 4386: 4381: 4376: 4371: 4366: 4361: 4356: 4351: 4346: 4341: 4336: 4331: 4326: 4321: 4316: 4311: 4306: 4300: 4298: 4294: 4293: 4291: 4290: 4285: 4280: 4275: 4270: 4265: 4260: 4255: 4250: 4245: 4240: 4235: 4230: 4225: 4219: 4217: 4213: 4212: 4201: 4200: 4193: 4186: 4178: 4172: 4171: 4161: 4151: 4143: 4142:External links 4140: 4137: 4136: 4129: 4105: 4102:. CS-RR-78-46. 4086: 4083:. p. 540. 4081:Addison-Wesley 4064: 4035: 4016: 3990: 3976: 3943: 3907: 3892: 3857: 3843: 3810: 3773: 3756: 3735: 3718:10.1.1.18.7520 3695: 3688: 3680:Addison-Wesley 3655: 3642:(April 1970), 3631: 3617: 3584: 3578:978-0201361209 3577: 3556: 3532: 3526: 3498: 3493:Probably Dance 3476: 3437: 3431:978-0849385230 3430: 3408: 3383: 3376: 3360:Addison-Wesley 3336: 3315: 3282: 3281: 3279: 3276: 3273: 3272: 3263: 3254: 3242: 3239: 3236: 3233: 3230: 3227: 3224: 3221: 3218: 3215: 3212: 3209: 3206: 3203: 3200: 3197: 3194: 3191: 3188: 3185: 3182: 3179: 3176: 3160: 3146: 3136: 3135: 3133: 3130: 3128: 3127: 3122: 3117: 3112: 3107: 3102: 3096: 3094: 3091: 3065: 3062: 3003: 3000: 2989:as well as in 2953: 2945: 2943: 2940: 2921: 2913: 2911: 2908: 2755:Main article: 2752: 2749: 2722: 2715: 2708: 2688: 2678: 2674:a + ⋯ + 2668: 2658: 2646: 2643: 2631: 2628: 2596: 2593: 2581: 2578: 2553: 2550: 2544: 2541: 2522:Albert Zobrist 2503: 2500: 2492: 2491: 2488: 2462: 2442: 2439: 2419: 2402: 2399: 2382: 2368: 2365: 2354: 2316: 2313: 2310: 2296:and for fixed 2292: 2260: 2179: 2171: 2168: 2163: 2160: 2113: 2103: 2090: 2073: 2062: 1975: 1970: 1966: 1962: 1959: 1956: 1951: 1948: 1945: 1941: 1937: 1934: 1931: 1928: 1925: 1765: 1761: 1755: 1745: 1728: 1718: 1705: 1680: 1670: 1657: 1640: 1636: 1630: 1620: 1607: 1597: 1561: 1558: 1518: 1515: 1474: 1471: 1457: 1454: 1440: 1437: 1397:extended ASCII 1348: 1345: 1339: 1336: 1325: 1322: 1280:spiral hashing 1276:Linear hashing 1200: 1197: 1173: − 1 1109: 1108:Variable range 1106: 1100: 1097: 1064: 1061: 1060: 1059: 1053: 1050: 1040: 1037:Key derivation 1034: 1020: 1017: 981:Main article: 978: 975: 885: 882: 860: 834: 828: 825: 822: 819: 816: 813: 810: 807: 804: 801: 798: 794: 790: 787: 782: 778: 774: 771: 768: 763: 759: 755: 752: 747: 743: 739: 734: 731: 728: 723: 720: 717: 713: 691: 688: 591: 588: 585: 584: 499: 497: 490: 484: 481: 466:image database 385:data structure 365: 362: 357:double hashing 349:linear probing 328:Main article: 325: 322: 301: 300: 297: 290: 270: 267: 255:data integrity 149: 148: 63: 61: 54: 26: 18:Hash algorithm 9: 6: 4: 3: 2: 4460: 4449: 4446: 4444: 4441: 4440: 4438: 4423: 4420: 4418: 4415: 4414: 4411: 4405: 4402: 4400: 4397: 4395: 4392: 4390: 4387: 4385: 4382: 4380: 4377: 4375: 4372: 4370: 4367: 4365: 4362: 4360: 4357: 4355: 4354:Hash function 4352: 4350: 4347: 4345: 4342: 4340: 4337: 4335: 4332: 4330: 4327: 4325: 4322: 4320: 4317: 4315: 4312: 4310: 4309:Binary search 4307: 4305: 4302: 4301: 4299: 4295: 4289: 4286: 4284: 4281: 4279: 4276: 4274: 4271: 4269: 4266: 4264: 4261: 4259: 4256: 4254: 4251: 4249: 4246: 4244: 4241: 4239: 4236: 4234: 4231: 4229: 4226: 4224: 4221: 4220: 4218: 4214: 4210: 4206: 4199: 4194: 4192: 4187: 4185: 4180: 4179: 4176: 4169: 4165: 4162: 4159: 4155: 4152: 4149: 4146: 4145: 4132: 4126: 4122: 4118: 4112: 4110: 4101: 4097: 4090: 4082: 4078: 4074: 4068: 4061: 4050: 4046: 4039: 4032: 4027: 4023: 4019: 4013: 4009: 4005: 4001: 3994: 3979: 3973: 3969: 3965: 3961: 3954: 3947: 3931: 3926: 3922: 3918: 3911: 3903: 3899: 3895: 3889: 3885: 3881: 3874: 3873: 3868: 3861: 3846: 3844:9781450356329 3840: 3836: 3832: 3828: 3821: 3814: 3799: 3795: 3791: 3784: 3777: 3770:. N.B. Singh. 3769: 3768: 3764:Singh, N. B. 3760: 3746: 3742: 3738: 3736:981-02-3107-5 3732: 3728: 3724: 3719: 3714: 3710: 3706: 3699: 3691: 3689:0-201-10088-6 3685: 3681: 3677: 3673: 3672:Ullman, J. D. 3669: 3665: 3659: 3647: 3646: 3641: 3635: 3627: 3621: 3612: 3607: 3603: 3599: 3595: 3588: 3580: 3574: 3570: 3563: 3561: 3546: 3542: 3536: 3529: 3523: 3518: 3513: 3509: 3502: 3494: 3490: 3483: 3481: 3472: 3468: 3464: 3460: 3456: 3452: 3448: 3441: 3433: 3427: 3424:. CRC Press. 3422: 3421: 3412: 3398: 3394: 3387: 3379: 3373: 3369: 3365: 3361: 3357: 3353: 3347: 3345: 3343: 3341: 3325: 3319: 3304: 3300: 3296: 3295: 3287: 3283: 3267: 3258: 3237: 3234: 3231: 3228: 3225: 3222: 3219: 3216: 3213: 3210: 3207: 3204: 3201: 3198: 3195: 3192: 3189: 3186: 3183: 3177: 3174: 3164: 3156: 3150: 3141: 3137: 3126: 3123: 3121: 3118: 3116: 3113: 3111: 3108: 3106: 3103: 3101: 3098: 3097: 3090: 3088: 3084: 3080: 3076: 3071: 3061: 3058: 3054: 3048: 3041: 3038: 3031: 3025: 3020: 3015: 3012: 2996: 2992: 2988: 2984: 2980: 2976: 2972: 2968: 2964: 2960: 2956: 2950: 2936: 2932: 2928: 2924: 2923:Fuzzy hashing 2918: 2917:Fuzzy hashing 2907: 2905: 2900: 2894: 2887: 2883: 2879: 2872: 2868: 2864: 2859: 2854: 2851: 2845: 2842: +  2841: 2835: 2829: 2825: 2819: 2813: 2809: 2803: 2797: 2791: 2786: 2781: 2775: 2770: 2764: 2758: 2748: 2740: 2734: 2725: 2721: 2714: 2707: 2699: 2695: 2687: 2683: 2677: 2671: 2667: 2661: 2657: 2652: 2642: 2637: 2627: 2624: 2622: 2618: 2617:"Dragon Book" 2614: 2610: 2606: 2601: 2592: 2588: 2577: 2575: 2571: 2567: 2563: 2559: 2549: 2540: 2538: 2533: 2529: 2525: 2523: 2519: 2513: 2509: 2499: 2447: 2443: 2407: 2403: 2373: 2369: 2350: 2346: 2345: 2344: 2341: 2337: 2334:(phi) is the 2321: 2309: 2305: 2291: 2289: 2276: 2268: 2263: 2259: 2254: 2244: 2237: 2228: 2221:. The value 2218: 2215:{0, …, 2207: 2203: 2199: 2195: 2187: 2182: 2178: 2167: 2159: 2148: 2140: 2136: 2129: 2125: 2112: 2108: 2102: 2098: 2093: 2089: 2085: 2081: 2072: 2065: 2058: 2051: 2047: 2041: 2030: 2026: 2022:is a root of 2014: 2009: 2005: 1998: 1994: 1968: 1964: 1960: 1957: 1949: 1946: 1943: 1939: 1935: 1929: 1923: 1914: 1911: 1907: 1903: 1899: 1895: 1888: 1884: 1881:{1,2,…, 1873: 1869: 1865: 1861: 1857: 1853: 1849: 1845: 1841: 1835:) = (15,10,7) 1834: 1830: 1826: 1820: 1813: 1789: 1777: 1773: 1760: 1754: 1748: 1744: 1740: 1736: 1727: 1723: 1717: 1713: 1708: 1704: 1700: 1696: 1692: 1688: 1679: 1675: 1669: 1665: 1660: 1656: 1652: 1648: 1635: 1629: 1623: 1619: 1615: 1605: 1600: 1595: 1591: 1587: 1576: 1557: 1555: 1549: 1541: 1537: 1533: 1529: 1514: 1470: 1453: 1436: 1427: 1423: 1418: 1406: 1402: 1398: 1394: 1390: 1385: 1367: 1362: 1360: 1356: 1355: 1344: 1335: 1332: 1321: 1319: 1314: 1310: 1306: 1302: 1296: 1290: 1285: 1281: 1277: 1273: 1269: 1265: 1258: 1254: 1250: 1246: 1242: 1238: 1232: 1226: 1219: 1215: 1211: 1205: 1196: 1194: 1193:prime numbers 1190: 1185: 1179: 1172: 1163: 1159: 1150: 1145: 1140: 1126: 1123: 1117: 1105: 1099:Defined range 1096: 1094: 1090: 1085: 1083: 1078: 1074: 1070: 1069:deterministic 1063:Deterministic 1057: 1054: 1051: 1048: 1044: 1041: 1038: 1035: 1032: 1029: 1028: 1027: 1024: 1019:Applicability 1016: 1012: 1006: 999: 994: 990: 984: 974: 970: 967: 963: 958: 952: 949: 942: 937: 934:. Consider a 928: 922: 916: 914: 911: 907: 903: 898: 894: 890: 881: 879: 874: 871: 863: 859: 845: 832: 823: 820: 817: 814: 811: 808: 799: 796: 792: 788: 780: 776: 769: 766: 761: 757: 745: 741: 732: 729: 726: 721: 718: 715: 711: 699: 697: 687: 685: 680: 676: 675: 669: 667: 662: 656: 650: 646: 640: 636: 630: 624: 618: 614: 612: 608: 603: 601: 597: 581: 578: 570: 559: 556: 552: 549: 545: 542: 538: 535: 531: 528: –  527: 523: 522:Find sources: 516: 512: 506: 505: 500:This section 498: 494: 489: 488: 480: 478: 474: 469: 468:, and so on. 467: 463: 459: 458:closest pairs 455: 451: 447: 443: 439: 435: 431: 427: 423: 422: 417: 413: 409: 405: 401: 396: 394: 390: 386: 383: 382:probabilistic 379: 374: 371: 361: 358: 354: 350: 346: 342: 337: 331: 321: 319: 314: 310: 306: 298: 295: 291: 288: 284: 280: 279: 278: 275: 266: 264: 260: 256: 252: 248: 244: 240: 236: 232: 228: 223: 221: 216: 212: 210: 206: 202: 201: 196: 192: 188: 184: 180: 176: 172: 168: 167:hash function 160: 155: 145: 142: 134: 123: 120: 116: 113: 109: 106: 102: 99: 95: 92: –  91: 87: 86:Find sources: 80: 76: 70: 69: 64:This article 62: 58: 53: 52: 47: 40: 33: 19: 4379:Root-finding 4353: 4304:Backtracking 4268:Segment tree 4238:Fenwick tree 4150:by Timo Denk 4120: 4095: 4089: 4076: 4067: 4058: 4052:. Retrieved 4048: 4038: 4029: 3999: 3993: 3983:December 12, 3981:. Retrieved 3959: 3946: 3934:. Retrieved 3920: 3910: 3871: 3860: 3850:December 12, 3848:. Retrieved 3826: 3813: 3801:. Retrieved 3789: 3776: 3766: 3759: 3748:. Retrieved 3708: 3698: 3675: 3658: 3644: 3634: 3620: 3601: 3597: 3587: 3568: 3548:. Retrieved 3544: 3535: 3507: 3501: 3492: 3450: 3446: 3440: 3419: 3411: 3400:. Retrieved 3397:Ars Technica 3396: 3386: 3355: 3327:. Retrieved 3318: 3306:. Retrieved 3293: 3286: 3266: 3257: 3163: 3149: 3140: 3086: 3075:Donald Knuth 3069: 3067: 3056: 3052: 3046: 3039: 3036: 3029: 3023: 3016: 3010: 3005: 2898: 2892: 2885: 2881: 2877: 2870: 2866: 2862: 2855: 2849: 2843: 2839: 2833: 2827: 2823: 2817: 2811: 2807: 2801: 2795: 2789: 2779: 2773: 2766: 2757:Rolling hash 2751:Rolling hash 2738: 2732: 2723: 2719: 2712: 2705: 2697: 2685: 2681: 2675: 2669: 2665: 2659: 2655: 2648: 2639: 2625: 2602: 2598: 2586: 2583: 2555: 2546: 2536: 2534: 2530: 2526: 2517: 2515: 2493: 2445: 2405: 2371: 2348: 2336:golden ratio 2318: 2306: 2295: 2274: 2266: 2261: 2257: 2242: 2235: 2216: 2205: 2201: 2197: 2193: 2185: 2180: 2176: 2173: 2165: 2149: 2138: 2134: 2127: 2123: 2110: 2106: 2100: 2099:+ ⋯ + 2096: 2091: 2087: 2083: 2079: 2070: 2063: 2056: 2049: 2045: 2039: 2028: 2024: 2012: 2007: 2003: 1996: 1992: 1915: 1909: 1905: 1901: 1897: 1893: 1886: 1882: 1874: 1867: 1863: 1859: 1855: 1851: 1847: 1843: 1839: 1832: 1828: 1824: 1812:finite field 1790: 1775: 1771: 1758: 1752: 1746: 1742: 1738: 1734: 1725: 1721: 1715: 1711: 1706: 1702: 1698: 1694: 1690: 1686: 1677: 1673: 1667: 1666:+ ⋯ + 1663: 1658: 1654: 1650: 1646: 1633: 1627: 1621: 1617: 1613: 1603: 1598: 1593: 1589: 1585: 1574: 1563: 1547: 1539: 1535: 1531: 1527: 1520: 1476: 1464:bits, where 1459: 1442: 1419: 1386: 1363: 1352: 1350: 1341: 1327: 1315: 1308: 1304: 1300: 1294: 1288: 1274: 1267: 1263: 1256: 1252: 1248: 1244: 1240: 1236: 1230: 1224: 1217: 1213: 1209: 1206: 1202: 1183: 1177: 1170: 1162:bit shifting 1148: 1138: 1127: 1121: 1115: 1111: 1102: 1086: 1066: 1025: 1022: 1010: 1004: 997: 991:scheme is a 988: 986: 977:Universality 971: 965: 961: 950: 947: 940: 926: 920: 917: 899: 895: 891: 887: 875: 872: 861: 857: 846: 700: 693: 672: 670: 660: 654: 648: 644: 638: 634: 628: 622: 619: 615: 610: 606: 604: 599: 593: 573: 567:October 2017 564: 554: 547: 540: 533: 521: 509:Please help 504:verification 501: 477:dynamic sets 470: 429: 425: 419: 415: 408:metric space 403: 397: 378:Bloom filter 375: 367: 344: 340: 333: 318:linked lists 313:pathological 302: 283:machine-word 276: 272: 235:fingerprints 231:check digits 224: 217: 213: 208: 204: 198: 194: 193:, or simply 190: 187:hash digests 186: 182: 178: 166: 164: 137: 128: 118: 111: 104: 97: 85: 73:Please help 68:verification 65: 4258:Linked list 3803:January 11, 3308:January 24, 2963:fingerprint 2787:of a given 2783:-character 1808:2 − 1 1473:Mid-squares 1401:ISO Latin 1 1331:equivalence 1158:bit masking 596:probability 430:bucket grid 404:grid method 336:hash tables 324:Hash tables 179:hash values 4437:Categories 4394:Sweep line 4369:Randomized 4297:Algorithms 4248:Hash table 4209:algorithms 4054:2018-07-05 3750:2021-12-06 3550:2017-03-24 3402:2022-02-06 3329:January 1, 3278:References 3035:α / ( 2967:multimedia 2910:Fuzzy hash 2858:Rabin-Karp 2777:for every 2761:See also: 2634:See also: 2570:characters 2324:2 / ϕ 2277:mod 2) / 2 2219:− 1} 2010:) = | 1900:) ∈ 1885:} ⊆ 1714:+ ⋯ 1550:− 1} 1534:) ≡ 1056:Signatures 884:Efficiency 600:collisions 590:Uniformity 537:newspapers 483:Properties 426:grid index 330:Hash table 305:collisions 200:hash table 183:hash codes 101:newspapers 4389:Streaming 4374:Recursion 4049:pHash.org 4026:0302-9743 3713:CiteSeerX 3668:Sethi, R. 3604:: 59–65. 3115:Identicon 3068:The term 2995:watermark 2785:substring 2613:Bell Labs 2320:Fibonacci 2253:word size 2033:whenever 1965:α 1961:− 1947:∈ 1940:∏ 1611:. A key 1426:ZIP codes 1417:entries. 1329:the data 1144:remainder 957:bit shift 953:(key) / 2 938:function 821:− 730:− 712:∑ 679:factorial 664:—see the 421:grid file 412:partition 227:checksums 220:collision 159:collision 131:July 2010 4119:(2000). 4075:(1975). 3936:June 30, 3902:32568938 3674:(1986). 3471:18086276 3455:Elsevier 3354:(1973). 3158:entries. 3093:See also 3044:, where 3002:Analysis 2975:features 2672:−2 2662:−1 2605:PJW hash 2326:, where 2094:−1 2054:satisfy 2018:. Since 1908:∈ 1749:−1 1709:−1 1661:−1 1624:−1 1601:−1 1596:+ ζ 1568:bits to 1391:between 1384:cannot. 1354:identity 1073:function 1008:, where 294:keyspace 269:Overview 261:, while 171:function 32:HashLink 4384:Sorting 4359:Minimax 3745:8250194 3664:Aho, A. 3457:: 1–7. 3364:Bibcode 3064:History 1916:Define 1904:∀ 1837:yields 1751:… 1732:. Then 1626:… 1456:Folding 1405:Unicode 1370:Integer 1359:perfect 1222:(where 1187:, e.g. 1093:SipHash 674:perfect 551:scholar 448:in the 402:or the 389:element 251:ciphers 205:hashing 191:digests 169:is any 115:scholar 4364:Online 4349:Greedy 4278:String 4127:  4024:  4014:  3974:  3900:  3890:  3841:  3743:  3733:  3715:  3686:  3575:  3524:  3469:  3428:  3374:  3153:Plain 3047:α 3017:While 2847:where 2651:EBCDIC 2572:, and 2520:after 2340:blocks 2332:ϕ 2035:α 2020:α 2016:| 1986:where 1802:, and 1693:) mod 1382:Double 1089:Python 906:modulo 847:where 611:random 609:, not 553:  546:  539:  532:  524:  464:in an 462:images 452:or in 370:caches 249:, and 195:hashes 117:  110:  103:  96:  88:  4273:Stack 4263:Queue 4243:Graph 4223:Array 3956:(PDF) 3898:S2CID 3876:(PDF) 3823:(PDF) 3786:(PDF) 3741:S2CID 3649:(PDF) 3467:S2CID 3453:(1). 3155:ASCII 3132:Notes 3019:Knuth 2810:> 2718:,..., 2694:radix 2621:xored 2444:64: 2404:48: 2370:32: 2347:16: 2200:) / ( 1819:Knuth 1815:GF(2) 1769:. If 1741:) = ( 1538:(mod 1374:Float 1146:. 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collision
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collision
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fingerprints
lossy compression
randomization functions
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