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In cryptography, collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b but H(a) = H(b).
This property is sometimes referred to as strong collision resistance. It requires a hash value at least twice as long as that required for pre-image resistance; otherwise, collisions may be found by a birthday attack. [4] Collision resistance implies second pre-image resistance but does not imply pre-image resistance. [5]
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.
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 ...
Collisions originally reported in 2004, [13] followed up by cryptanalysis paper in 2005. [19] RadioGatún: Up to 2 608 [20] 2 704: 2008-12-04 For a word size w between 1-64 bits, the hash provides a security claim of 2 9.5w. The attack can find a collision in 2 11w time. [21] RIPEMD-160 2 80: 48 of 80 rounds (2 51 time) 2006 Paper. [22] SHA-0: ...
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]
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 ...
Second-preimage resistance implies preimage resistance only if the size of the hash function's inputs can be substantially (e.g., factor 2) larger than the size of the hash function's outputs. [1] Conversely, a second-preimage attack implies a collision attack (trivially, since, in addition to x ′ , x is already known right from the start).