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Comment by afsina | Hacker News Reader

These are not cryptographic hashes. Comparison would be unfair as cryptographic ones are rather slow . These are used in structures like Hash tables or Bloom Filters etc. they need to be very fast and provide reasonable randomness (low collision). Bu their collision rates are very high comparing to say SHA1.

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Still it would be useful to see them as a point of reference - to determine whether it's worth bothering with anything else in first place.

I thought MD5 and SHA-1 were both designed as cryptographic hashes but now deprecated for this purpose - although SHA-1 is still used in applications such as git as a general purpose hash function.

Neither are recommended for modern security needs, but MD5 is way, way more broken than SHA1. As far as I know, no SHA1 collision has ever been found, whereas any cs undergrad could implement arbitrary MD5 collisions using some work done by a Chinese team a few years back. SHA1 is deprecated because of some theoretical attacks which lower the complexity of finding a collision without really making it a tractable problem.

It'd still be interesting, particularly in a world where hardware is picking up the load for things which SSL uses. I'd expect the answer to be something along the lines of “more competitive as the data size increases” but it'd be interesting to know how great the margin is and whether the answer shifts significantly when comparing, say, a conventional hash to a cryptographic one on an embedded chip.

>@Orbling, for implementation of a hash dictionary. So collisions should be kept to a minimal, but it has no security purpose at all. – Earlz

SHA-1 is very fast though so it is a good point for comparison.

SHA-1 was designed as a cryptographic hash functions, they are puprposely slow. No, SHA-1 is not as fast as functions from the article.

You've got it backwards; cryptographic hash functions are designed to be as fast as possible without giving up their cryptographic properties. If you need a slow hash (e.g. for password storage), you use something like bcrypt that's designed to be slow.

> SHA-1 is very fast though

SHA-1 is fast for a cryptographic hash function, but it's orders of magnitude slower than "hashmap" hashes. crc32 is more than an order of magnitude faster, and as you can see in TFA's table it's ~half the speed of the best non-crypto hashes.

There are, however, applications with both hash tables and bloom filters where some cryptographic properties are still useful/necessary, or where low-collision hashes are particularly important.

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