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One-way hash function, sometimes also called as one-way compression function—compute a reduced hash value for a message (e.g., SHA-256) Symmetric key cryptography—compute a ciphertext decodable with the same key used to encode (e.g., AES) Public-key cryptography—compute a ciphertext decodable with a different key used to encode (e.g., RSA)
In cryptography and computer security, a length extension attack is a type of attack where an attacker can use Hash(message 1) and the length of message 1 to calculate Hash(message 1 ‖ message 2) for an attacker-controlled message 2, without needing to know the content of message 1.
SHA-2 basically consists of two hash algorithms: SHA-256 and SHA-512. SHA-224 is a variant of SHA-256 with different starting values and truncated output. SHA-384 and the lesser-known SHA-512/224 and SHA-512/256 are all variants of SHA-512. SHA-512 is more secure than SHA-256 and is commonly faster than SHA-256 on 64-bit machines such as AMD64.
In cryptography, the avalanche effect is the desirable property of cryptographic algorithms, typically block ciphers [1] and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip).
For example, in the above picture hash 0 is the result of hashing the concatenation of hash 0-0 and hash 0-1. That is, hash 0 = hash ( hash 0-0 + hash 0-1 ) where "+" denotes concatenation. Most hash tree implementations are binary (two child nodes under each node) but they can just as well use many more child nodes under each node.
In computer science, a hash collision or hash clash [1] is when two distinct pieces of data in a hash table share the same hash value. The hash value in this case is derived from a hash function which takes a data input and returns a fixed length of bits. [2]
A mask generation function (MGF) is a cryptographic primitive similar to a cryptographic hash function except that while a hash function's output has a fixed size, a MGF supports output of a variable length.
[1] It is formally described in RFC 5869. [2] One of its authors also described the algorithm in a companion paper in 2010. [1] NIST SP800-56Cr2 [3] specifies a parameterizable extract-then-expand scheme, noting that RFC 5869 HKDF is a version of it and citing its paper [1] for the rationale for the recommendations' extract-and-expand mechanisms.