So the other day I wondered the consequences when choosing one hashing method over another when it comes to security. If we say that some hacker has got a hold of your (of course!) encrypted fx passwords then what will it matter that you choose a unbroken, uncommon and maybe slower encryption method?
Speed
I started with some benchmarking: http://e-x-e.dk/labs/timing/ (source: http://www.e-x-e.dk/labs/timing/source.php).
This basically creates 10000 random strings with a length of 50 and then encrypting all of these random strings with all of the hashing methods of my php installation’s disposal. This outputs a sorted list of the methods. The consequents of choosing fx a slow hashing method means that you’ll have a bit more load on your server since speed == load. But then again, choosing a slow hashing method will also mean a slower bruteforce for the hacker – buying your users (or you) more time to change their passwords and you closing the hole. But you’ll have to remember that where your bigger load/increased hashing-time caused by the slower hashing method is spread out the bruteforcers isn’t. So it’ll be a bigger hit to the bruteforcer than it will be to you.
Common vs. uncommon method
When choosing a hashing method it can also be a benefit from my point of view to choose a less common method for hashing your password/information if you have the option. And the argument is quite simple I think. With common methods like md5 which is used by the majority of sites today there are already constructed huge (HUGE) rainbow tables etc. (http://www.freerainbowtables.com/da/tables/md5/). Therefore by choosing a common hashing method you are also decreasing it effectiveness since a lot of the string combinations have already been computed.
Choosing a more uncommon hashing method will get rid of this problem, but then again, this maybe result in a slower computing of the hash as well, and for some – that’s a problem. By choosing a fx a tiger(2), SHA-1 or SHA-512 hash over fx. md5 you would decrease the effectiveness/speed of the bruteforce.
Hash method attacks
The effectiveness of a hash method is of course also influenced by if it has been fx collision attacked (http://en.wikipedia.org/wiki/Collision_attack) or a preimage attack (http://en.wikipedia.org/wiki/Preimage_attack). Therefore you should also have this in your considerations when choosing a hashing method for your site.
Other things to consider
Things like salting your passwords etc etc is naturally also a good idea (maybe even with some HUGE salts, to ensure the length of the password extends the typical length of passwords and thereby setting the rainbow tables out of play). Some of these considerations might come in a later post.
I think there a lot fo pros and cons in this matter but as a general conclusion I think it’s time for the use of some more uncommon hashing methods in order to strengthen the security of information if hashed information is compromised. What do you think is the best hashing method to use and why?
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