Maybe the person who posted the exploit/solution was the person who created the ransomware? That way they get BTC from people who pay and donations from people who wait?

/krazyconspiracy :-P

If I was an aspiring ransomware writer, I'd extract _a lot_ of useful ideas from this thread. :P

The targets for this malware are laypeople with enough funds to pay the fee but not enough to go after the creators. Hypothetically, if a national government or other agent with sufficiently deep pockets were infected they would first attempt to crack it, failing that they would go after the creators directly- they would not pay the fee.

So implementing weak crypto dramatically lowers the risk of prosecution or worse for the attackers.

Maybe not deliberate, but most likely optimizing encrypting speed over stronger encryption. Better for hit and runs I guess.

To add to the suppositions: perhaps the author was afraid they may get bitten by their own malware and designed in a weakness as a backdoor in case they lost access to the key server and needed to decrypt their own drive.

This is my favourite of all the answers, because it would mean that the dev would have known how incompetent s/he was, and thus made a weak system in order to account for the likelihood of a "self-inflicted wound".

Here's one...maybe the actual developer who was contracted to build the damned thing purposely used weak encryption to try to ameliorate his/her part in making this malware mess.

Well, I can't say that it's deliberate, but it's definitely some "interesting" choices.

A reasonable Salsa20/20 implementation on a modest processor encrypts on the order of 400MiB/s [0][1]. So that the author went to the trouble of halving the number of rounds and changing the word-size when there are perfectly good and plenty fast off-the-shelf Salsa implementations strikes me as rather strange. Surely this is not the bottleneck on most employee's machines.

And then there's the apparently tiny keyspace used. You could argue that this makes the key more "user-friendly" (!), but just a hex representation of a random 256bit key would seem much more natural, and the poor targets are hardly in a position to complain.

[0] https://www.cryptopp.com/benchmarks.html [1] https://cr.yp.to/snuffle.html

Actually customer service is very important to these operations. They have to create trust that paying will relieve your machine of their infliction.

Maybe they wanted to keep CPU usage low? Although disk usage would be noticeable as well (usually).