A hash function is any function that can be used to map data of arbitrary size to data of fixed size. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. Hash functions are a fundamental part of modern cryptography. They are also widely used in many other applications where efficient data lookup is critical.
A hash function is any function that can be used to map data of arbitrary size to data of fixed size. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes.
Hash functions are a fundamental part of modern cryptography. They are also widely used in many other applications where efficient data lookup is critical.
A hash function takes a piece of data as input and produces a hash value as output. The input data can be of any size, but the output hash value is always of fixed size.
The input data is often called the message, and the output hash value is often called the message digest or simply the digest.
A cryptographic hash function is a hash function that is resistant to cryptographic attacks. In other words, it is hard to find two different pieces of data that produce the same hash value.
Cryptographic hash functions are used in digital signatures, message authentication codes, and other security applications.
A non-cryptographic hash function is a hash function that is not resistant to cryptographic attacks. In other words, it is easy to find two different pieces of data that produce the same hash value.
Non-cryptographic hash functions are used in data structures such as hash tables and digital content distribution.
A hash function can be implemented in any programming language. The most common hash functions are implemented in the C programming language.
A good hash function should have the following properties:
There are two types of hash functions:
Hash functions are used in the following applications:
A hash table is a data structure that is used to store data in a key-value format. The keys are used to index the data, and the values are the data that is stored.
Hash tables are used to implement hash functions. The keys in a hash table are the input data, and the values are the output hash values.
Hash tables are used in many applications, such as databases and web applications.
A hash function collision is when two pieces of data produce the same hash value. Hash function collisions are unavoidable, but they should be rare.
Hash function collisions can cause problems in applications that use hash functions, such as hash tables.
There are two ways to avoid hash function collisions:
A perfect hash function is a hash function that maps all of the input data to unique output hash values. Perfect hash functions are impossible to find, but they can be approximated.
A hash function attack is an attempt to find two pieces of data that produce the same hash value. Hash function attacks are often used to find collisions.
Hash function attacks can be used to find collisions in cryptographic hash functions. This can be used to forge digital signatures and to impersonate other users.
Hash function attacks can also be used to find collisions in non-cryptographic hash functions. This can be used to cause denial-of-service attacks.
A rainbow table is a data structure that is used to store the results of hash function collisions. Rainbow tables are used to speed up hash function attacks.
Hash function security is the study of hash functions that are resistant to cryptographic attacks. Hash function security is a branch of cryptography.