Cisco Cyber Security Practice Exam

What is a key property of a hash function?

1. Reversible

2. One-way

3. Two-way

4. Randomized

The correct answer is: One-way

A hash function is a fundamental concept in cybersecurity and cryptography, and its key property is that it is one-way. This means that once data is processed through a hash function, it produces a fixed-size output that cannot easily be reversed to reveal the original input. The design of a hash function ensures that even a tiny change in the input results in a significantly different output, which is known as the avalanche effect. This property makes hash functions particularly useful for data integrity verification, password storage, and digital signatures. The one-way nature of hash functions is essential for security. For example, when a user creates a password, that password is hashed and stored. During the authentication process, the input password is hashed again, and if the resulting hash matches the stored hash, access is granted. Because the original password cannot be easily derived from the hash, even if an attacker gains access to the hashes, they cannot reverse-engineer them to find out the passwords. In contrast, the other options describe properties that do not apply to secure hash functions. The concept of being "reversible" or "two-way" is associated with encryption algorithms, where the original data can be recovered with the appropriate key. "Randomized" relates more to certain cryptographic functions