Which property ensures that a hash function will not produce the same hashed value for two different messages?

Collision resistance is a formal cryptographic property defined as the computational infeasibility of finding two distinct inputs that hash to the same value. A hash function without this property would allow an attacker to substitute one message for another while keeping the same digest, undermining integrity verification. This is distinct from other properties like preimage resistance and is a core requirement in cryptographic hash standards.

Bit length describes the size of the hash output and affects the probability of collisions statistically, but it does not itself enforce or guarantee collision resistance as a cryptographic property.

Key strength applies to symmetric and asymmetric encryption algorithms, not to hash functions, which by design do not use keys.

Entropy describes the unpredictability or randomness of data and relates to password strength or key generation, not the collision-resistance property of a hash function.