[marshray]

> Md5 is just as fine as any other generic hash function if its being used as a non-unique key

MD5 brings the feature that you'll forever be explaining why you chose a function that had already been broken for 30 years when other options were readily available.

[StillBored]

Often, its less about picking it for a new project vs having the discussion about how to update an existing one, often with data at rest that needs converting. In the latter case often the hash needs to fit into the existing 128b field size, so one is throwing a good number of the SHA bits away anyway.

[marshray]

This is not a justification for using a broken function.

Truncating a fixed number of bits does not make a good secure function less secure, other than the implications that the shorter length has on brute-force and collision strength.

In some cases it can even make it even more secure, e.g. SHA-2-512/256.

[StillBored]

Uh, truncation is a huge no-no for security. But, that isn't what I was talking about. For deduplication/hash key/etc kinds of functions where a checksum works (or some other algorithm with a high chance of collisions is implemented for unit testing to assure collision paths are handled correctly).

This is part of the entire discussion, it's possible to use algorithms originally intended for cryptographically secure purposes in places where the reversibility/collision properties aren't considered problems. And likely this will only happen more frequently as algorithms are picked because they have hardware acceleration and are fast rather for the underlying security properties.

BTW: There is a fun game that I've played; see how much you can truncate a modern cryptographic hash before it becomes trivial to find collisions.