Dude. You’d break crypto for payment in.... crypto?

Why not just create transfers quietly from others and bleed out wallets from around the world, then convert to cash, then publish? You’d be rich, crypto would crash, and you’d be able to buy a lifetime supply of popcorn for the ensuing collapse.

You're going to have to launder a lot of money. What's your strategy there?

No need to launder, this money would not be illegal. Just convert it and pay your taxes. When you will have to justify your revenues, everybody will have migrated to different cryptography anyway and you will not be in danger any more and you will be able to use this money as you want.

Because there will be fifteen nation-states who want to kidnap you and force you to disclose the algorithm?

Just Tarex teams and Mossad by themselves would be a big threat. NSA has the visibility to de-anonymize even some people on Tor. Most mathematicians aren't exactly computer security geniuses. NSA might not even need to work that hard. Then, they have plenty of partners for grabbing whoever or whatever the target is.

https://theintercept.com/2014/10/10/core-secrets/

You don't have to keep it private after 2/3 months. Just make the algorithm public and no one will kidnap you.

Why launder? Plenty of goods and services would accept crypto as payment. No need to launder cryptocurrencies but the wild swings in price will affect your accounting in your business.

I'm not very familiar with cryptocurrencies, but wouldn't you be able to also crack crypto wallets? If so, wouldn't the value of crypto go down to 0 thanks to your service?

Cracking RSA isn't cracking SHA-256. Bitcoin and other coins are based on SHA-256. If someone were able to crack SHA-256, the exploit would be better served (of the hacker) to slowly steal coins, so that value within the network is maintained and the exploit is overlooked and missed by the majority. In addition to stealing national secrets.

But all you'd need to do is steal from one early adopter (it's in their financial interest to be savvy enough) and the adopter could alarm the community that an exploit is in existence.

In addition, there are various cryptographic algorithms used. So, one could accept Litecoin, if SHA-256 was exploited. Or accept Vertcoin if both Script and SHA-256 was exploited. Etc.

So, it's an interesting situation based on game theory of an exploit. There is no hard and fast answer.

The moment you have spent from an address, you have revealed the un-hashed key, which you could break. Best practice is never to re-use address, but I'd wager there are many deviuations from that. I'm not sure how much bitcoin that has moved in e.g. the last year is in addresses for which the private key is known. Would be a cool thing to check out.

It’s not about the hashes, i.e. the proof of work part, it’s about the fact that bitcoin addresses are public/private key cryptography, like RSA.

Now I think bitcoin actually uses es elliptic curve cryptography (I don’t know, I really don’t care about bitcoin), but the hypothetical was more along the lines of “what if you could break public/private key cryptography”, and less about factorization in specific, anyway.

Hmm. SHA-256 will be sunsetting probably within our lifetime due to the exponential nature of our computers. Which is probably why I assumed you'd be speaking about that function.

But a break in ECC would be...something extreme IMHO and according to multiple researchers, I believe, would happen after SHA-256 because ECC is more settled mathematics.

Bitcoin uses an elliptic curve algorithm secp256k1 for signing. This would be the relevant thing to break to take control of wallets.

presumably this darknet service to decrypt RSA is being used for nefarious purposes. i suppose you could prevent yourself from having access to the stuff people are decrypting and hope some kind of safe-harbor law would protect you.

Is it illegal to break encryption by brute force?

Intent matters. If you are breaking encryption to steal stuff, that is (and should be) illegal.

I think the real question here should be whether it is immoral though, because it is trivially illegal. Consider the DMCA and penalties for circumventing DRM. Heck, if you are decrypting stuff that is classified, intent might not even matter.

Use a mixer.

Tor offers a high, but ultimately limited amount of protection. I wouldn't count on it to protect something as enormous as this.