[cbsmith]

I think I was pretty clear that extension attacks work. I was clear that they work despite features of a hash algorithm that would appear to address the issues highlighted in the article. I was also very clear that it is the defender's problems that are deceptively hard.

In a couple of cases I probably should have said "simple" instead of "easy". "Easy" implies more about effort than complexity. At some points I meant "little effort" and other points I meant "little complexity", but I used the same word for both, so that's bad.

Still, I don't get how you inferred the above from this, which to me reads as "any efforts you might make to address this problem your own way will almost certainly fail miserably":

It's just not nearly as easy as this article suggests, and conclusions one might draw from this article (like you can solve this problem by feeding all source text in to the hash algorithm backwards) are likely ill founded.

[tptacek]

I think your comments have been misleading, so I corrected them. Nothing personal.