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In words, when given an x, it is not possible to find another x' such that the hashing function would create a collision. A hash function has strong collision resistance when, given a hashing function H, no arbitrary x and x' can be found where H(x)=H(x'). In words, no two x's can be found where the hashing function would create a collision.
John Smith and Sandra Dee share the same hash value of 02, causing a hash collision. 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]
Here is the formal technical definition of the puzzle friendliness property. [2] [1]A hash function H is said to be puzzle friendly if for every possible n-bit output value y, if k is chosen with a distribution with high min-entropy, then it is infeasible to find x such that H( k || x) = y (where the symbol "||" denotes concatenation) in time significantly less than 2 n.
In cryptography a universal one-way hash function (UOWHF, often pronounced "woof") is a type of universal hash function of particular importance to cryptography. UOWHFs are proposed as an alternative to collision-resistant hash functions (CRHFs). CRHFs have a strong collision-resistance property: that it is hard, given randomly chosen hash ...
keyed hash function (prefix-MAC) BLAKE3: 256 bits keyed hash function (supplied IV) HMAC: KMAC: arbitrary based on Keccak MD6: 512 bits Merkle tree NLFSR: One-key MAC (OMAC; CMAC) PMAC (cryptography) Poly1305-AES: 128 bits nonce-based SipHash: 32, 64 or 128 bits non-collision-resistant PRF: HighwayHash [16] 64, 128 or 256 bits non-collision ...
Generally, the basic security of cryptographic hash functions can be seen from different angles: pre-image resistance, second pre-image resistance, collision resistance, and pseudo-randomness. Pre-image resistance: given a hash h, it should be hard to find any message m such that h = hash(m). This concept is related to that of the one-way function.
The compression function can either be specially designed for hashing or be built from a block cipher. A hash function built with the Merkle–Damgård construction is as resistant to collisions as is its compression function; any collision for the full hash function can be traced back to a collision in the compression function.
An extension of the collision attack is the chosen-prefix collision attack, which is specific to Merkle–Damgård hash functions.In this case, the attacker can choose two arbitrarily different documents, and then append different calculated values that result in the whole documents having an equal hash value.