FWIW, the first warnings that SHA-1 was insecure and "It's time for us all to migrate away from SHA-1." were published prior to git's initial 2005 release: https://www.schneier.com/blog/archives/2005/02/cryptanalysis...

Because as we know, the security industry isn't a firehose of fear about everything that isn't airgapped (and then airgapping itself). Security recommendations come so thick and fast that even security researchers themselves don't bother following them. Even the bloke in your link explicitly apologises for using Word for some things, and he's considered a saint in the industry.

What all the commenters here doing a hatchet-job on Torvalds are missing is that he's saying "show me the money"/"perfect is the enemy of good". The hatchet-jobbers are too busy doing the usual tittering over his language to actually absorb the point.

Security industry != crypto academia.

Clearly, Linus didn't know at the time. If he'd know, he would have chosen another hash in 3 seconds —no additional complexity, no additional effort involved in not choosing a hash the security community starts to have doubts about.

Don't forget the extra computation cost with a more complex hash.

Nobody cares. Hashes are plenty fast. Even the code complexity doesn't matter: I've implemented both SHA-256, and SHA-512, take less than a hundred lines of code. And of course, Linus would have use some existing implementation.

Also, "more secure" doesn't necessarily mean "more complex", or "slower". Blake2b for instance is as fast as md5 and has a simple RAX (xor, rot, add) core from Chacha20.

It wasn't like that in 2005.

Which is largely irrelevant on desktops. Nobody's using git on embedded devices, so hash computational cost shouldn't be the deciding factor. Maybe people storing BLOBs will notice.

There are blobs in the kernel and speed was a very important motivation when kernel switched to git.

So now we need to assess whether hashes are a significant bottleneck.

I don't think that comparison is quite right: ten years ago we already had two of Xiaoyun Wang's attacks which significantly reduced the work factor to break SHA-1. They were already cited at the time as reasons to move away from the algorithm (and I doubt we'd be able to do the 2⁸⁰ work needed to get a collision without cryptanalytic research! — notably the successful Stevens attack today reported performing a total of 2⁶³ hash operations while claiming to be "one of the largest computations ever completed").

There's also important concern about SHA-512 (which has led to SHA-3 and other options), but I'm not sure it can be put in the same category; at least all of the best attacks today are significantly reduced-round.

https://en.wikipedia.org/wiki/SHA-2#Cryptanalysis_and_valida...

By contrast, Wang's original attack (which we had more than 10 years ago) achieved a 2¹¹ speedup for collisions against full SHA-1 and her second attack later the same year achieved 2¹⁷ speedup.

Evidently the speedup for the final version of Stevens's attack (which worked) was also around 2¹⁷. By contrast, a Moore's law improvement over 10 years would only be expected to make computers around 2⁶ times faster! (At the risk of mixed or mangled metaphors, we might say that mathematical insight during the time period you mention has been about 2¹¹ times more useful for attacking SHA-1 than computer power increases.)

Edit: someone else linked to Valerie Aurora's chart, which I'd forgotten about, which gives a synopsis of the historical status of the most popular hashes. On that chart, SHA-1 from 2005 was one category worse ("Weakened") than SHA-512 is today ("Minor weakness").

http://valerieaurora.org/hash.html

Something that bothers me is, why don't there exist dynamic encryption that scales with the current computing power? Then we might have less of a migration mess. Hope is that encryption breakers have to win by algorithmic strength rather than brute force "add more cores".