What is a birthday attack in cryptography?
D5 · Crypto · CompTIA Security+ SY0-701A birthday attack exploits the birthday paradox — the surprising probability that in a group of 23 people, two share a birthday (50% chance). Applied to cryptography, it finds two different inputs that produce the same hash output (a collision).
A collision attack against a hash function undermines its integrity guarantees — an attacker could substitute a malicious document with the same hash as a legitimate one.
Why MD5 and SHA-1 are broken: collision attacks have been demonstrated against both.
A collision attack against a hash function undermines its integrity guarantees — an attacker could substitute a malicious document with the same hash as a legitimate one.
Why MD5 and SHA-1 are broken: collision attacks have been demonstrated against both.
Birthday attacks target hash functions, not encryption. Defense: use longer hash outputs (SHA-256 or higher). A 128-bit hash has effective collision resistance of 64 bits due to the birthday bound. SHA-256 provides 128 bits of collision resistance.