What is one of the main properties of a one-way hash function?

• A. Easy to reverse
• B. Produces random outputs
• C. Only one input can produce that output
• D. Resistant to collisions

Answer: (D)

A main property of a one-way hash function is that it is resistant to collisions. This means that it is computationally infeasible to find two different inputs that produce the same hash output. In practice, this property is crucial for maintaining data integrity and ensuring that each unique input consistently generates a unique hash value, which is essential for tasks such as digital signatures and data verification.

When a hash function is collision-resistant, it helps prevent various types of attacks, such as preimage attacks, where an attacker could try to find an input corresponding to a specific hash output. Therefore, collision resistance is a fundamental characteristic that distinguishes a secure hash function from one that is not secure.