What Is a Collision Attack and How Does It Relate to Hash Function Security?

A collision attack occurs when an attacker finds two different inputs that produce the exact same hash output. For a secure hash function, this should be computationally infeasible.

If a collision is found, it compromises the integrity of the system, as one input could be maliciously replaced with the other without changing the hash. This is why strong collision resistance is a requirement for cryptocurrencies, as a collision could allow forging transactions.