Which type of hash is not recommended due to hash collisions?

The choice of MD5 as the type of hash that is not recommended due to hash collisions is accurate. MD5 (Message Digest Algorithm 5) was widely used for ensuring data integrity; however, it has significant vulnerabilities. Specifically, researchers have demonstrated that it is feasible to generate two different inputs that produce the same MD5 hash, an event known as a hash collision. This flaw leads to serious security implications because it can be exploited by attackers to create malicious files that align with legitimate files, thereby bypassing integrity checks.

Because of these vulnerabilities, MD5 is no longer considered a secure hashing algorithm for applications that require strong data integrity, such as cryptographic signatures or verification of data authenticity. Security practices have since shifted towards using more secure hashing algorithms like SHA-256, which has not been found vulnerable to similar attacks as MD5. Hence, MD5 is typically advised against in modern cryptographic practices.