On 3/21/13 4:30 PM, Roman Cheplyaka wrote:

* Thomas Moertel [2013-03-21 15:58:58-0400]

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On Wed, Mar 20, 2013 at 5:05 PM, Johan Tibell wrote:

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The problem is that if the secure hashing makes HashMap as slow as Map, there's no point in having the former in the first place, as it only exists to provide speed.

I understand that HashMap exists to provide speed, but are we sure that everyone who uses it for speed understands the security implications?

Regardless of whether speed-first or security-first is the default, users of HashMap can be partitioned into two groups: those who knowingly choose between speed and security, and those who do not. For the first group, either default is safe because members of that group will have the opportunity to choose the other option. But for the second group, only security-first is safe: if it’s not the default, members of the second group won’t have the option to choose it.

Why not simply educate them by placing a prominent notice in the haddock?

+1. Whenever there's this split between knowing-choice and ignorance, my preferred solution is always to educate people. Sometimes there are cases where one side of the choice is obviously superior, or where it's too difficult to explain what is at stake for the choice. In these cases I'm a fan of preferring the "safe" choice, because (a) it's obvious, or (b) education is too costly. But that's not so clear for something like significant speed benefits (which are crucial for some, and nice for all) vs defense against DoS (which are crucial for some, but irrelevant to others). Given that both benefits are crucial for some, either we should have no default ---for fear of offending either side--- or we should ignore both of those parties (since they are of approximately equal prominence), in which case things fall back to nice-for-all vs irrelevant-to-others, which favors speed as the default. Thankfully, in Haskell we have enough polymorphism that it's feasible to eschew a default choice, and it's also feasible to override whatever the default is. That puts us in a much better place than most other languages faced with this choice. -- Live well, ~wren