What Is a “Hash Collision” and Why Is It a Critical Concern for Blockchain Security?

A hash collision occurs when two different input data sets produce the exact same output hash. In a blockchain, if a collision were found, an attacker could replace a valid transaction with a fraudulent one that has the same hash, maintaining the integrity of the Merkle Root and the block header.

This would allow undetected tampering with the ledger, fundamentally compromising the security and immutability of the entire blockchain system.