I wouldn't read too much into it. No new technology springs from a void, they all are developments of previous years / decades worth of foundational work. The NSA is possibly the world's most expert organization on things related to cryptography, so it's completely unsurprising that they would have looked at stuff like this before.
NSA had backdoor access (private key) to the early cryptography that was sold and used by businesses. This issue actually still prevails in today's infrastructure: (example) google controls the master key for gmail. Of course, blockchain with zero-proof resolves this (decentralized messaging), which would allow greater security for trade secrets.
I am not a crypto expert, but I don't think this response makes much sense. First of all because it doesn't seem to apply to anything we were talking about.
Secondly, Google knows about the contents of your GMail not because of any secret cryto backdoor, but because you are sending them unencrypted emails that they store in their database on their servers. You are using their application, of course they can look at it and see what's in it. You don't want them to? Okay, then pre-encrypt your message and copy the encrypted nonsense blob into GMail. Now they can't read it. They can still see the blob, but they won't understand what it says.
Yes it is known that the NSA had backdoored several crypto algorithms in several different ways. You can read about some of them starting here:
https://en.wikipedia.org/wiki/National_Security_Agency#Bypassing_encryptionIt is also reasonably suspected that they have unknown-to-the-public tricks that weaken several others. And that's part of the point, they know more than anyone else. They are a thousand times smarter and sneakier than you and I put together. So it's almost literally impossible to tell what they can do and what is just rumor.
Blockchain / cryptocurrencies are no more immune than their underlying cryto algorithms. Certainly not from decentralized messaging, that's a minor speed bump to them not a roadblock. And as a non-crypto-expert it's not clear to me what zero-knowledge proofs have to do with anything. Nor does zero-knowledge proofs have anything really to do with decentralized messaging.
All that being said, just because the NSA published a paper 20 years ago that laid some of the groundwork for cryptocurrencies means nothing about the security or vulnerability of blockchain / cryptocurrencies. The NSA
also has an interest in making sure strong crypto works so that no one
else can spy on
them. And banks don't want people to be able to steal from them, and software companies don't want to be at fault if software they sell to their customers ends up getting them hacked, etc. So there is a lot of work that goes into making sure that crypo algorithms actually are working as advertised, and presumably blockchain / cryptocurrencies would be using the best-available algorithms, not known-weak ones.
I could be wrong about everything and it could be that you know way more about this than I do, but I would caution people in general about just throwing around jargon and pretending it's a magic solution to a problem. Crypto is really hard and there are probably only tens of people worldwide who actually really truly know what they're talking about. If you're not one of them you basically have to trust that they're not missing something. But at the same time I don't have any reason to suspect that blockchain / cryptocurrencies are vulnerable to anything, and that article should not make anyone suspicious of anything either.
Edit: This is also why the FBI and anyone else who complains about why the government should have backdoors into crypto algorithms "for national security reasons" should be boo'd out of office. There is no such thing as a backdoor that only the "good guys" can use. Either crypto is strong and your bank transactions are secure and your blockchain works and your private messages are private and the website you are visiting is actually the real website it says it is, or it's not and it's only a matter of time before the "bad guys" figure out how to break it (if they havn't already). There is no in-between. Support politicians who support real crypto, literally the entire internet depends on it.