Birthday attacks are a class of brute-force techniques used in an attempt to solve a class of cryptographic hash function
problems. These methods take advantage of functions which, when supplied with a random
input, return one of 
equally likely values. By repeatedly evaluating the function for different inputs,
the same output is expected to be obtained after about 
evaluations.
Birthday Attack
See also
Birthday Problem, Cryptographic Hash FunctionExplore with Wolfram|Alpha
References
RSA Security. "Cryptography FAQ 2.4.6. What Are Some Techniques Against Hash Functions?" http://www.rsasecurity.com/rsalabs/faq/2-4-6.html.van Oorschot, P. and Wiener, M. "A Known Plaintext Attack on Two-Key Triple Encryption." In Advances in Cryptology--Eurocrypt '90. New York: Springer-Verlag, pp. 366-377, 1991.Yuval, G. "How to Swindle Rabin." Cryptologia 3, 187-189, Jul. 1979.Referenced on Wolfram|Alpha
Birthday AttackCite this as:
Weisstein, Eric W. "Birthday Attack." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/BirthdayAttack.html