What are the technical advantages of Ring Signatures (CryptoNote) compared to CoinJoin?

Which privacy technology provides a higher level of privacy and why?

What is the difference between "passive" and "active" participation in mixing?

up vote 3 down vote accepted

Note: this is based on darkcoin's use of Coinjoin, and Coinjoin itself is not necessarily vulnerable to spying by third parties (see the comment below by gmaxwell).

The main difference is whether you are trusting third parties to do the mixing for you, or not. Coinjoin relies on third parties, while cryptonote allows you to do the mixing yourself locally.

In the Coinjoin case, you have to trust the third parties to not log, to perform the mixing, and to be available when needed. In the Cryptonote case, once you have the blockchain, you can mix locally, with cryptographic proof.

In both cases, if you mix an output of yours with N other outputs, the ideal case is that each output is equiprobably mapped to the real output. For Coinjoin, getting more information that equiprobability depends on the above (whether the third parties were honest, kept logs, etc). In the Crptonote case, it depends on cracking the ring signature algorithm, wihch is well understood peer reviewed cryptography.

Other ways to get information over equiprobability typically apply to both Coinjoin and Cryptonote (ie, newer coins are more likely to move).

If we go beyond privacy, then a difference between Coinjoin and Cryptonote mixing is that Coinjoin needs others to mix with you when you do. If nobody else wants to mix coins on friday when you want/need to mix some, you can't mix. With Cryptonote, you can mix alone without interacting with any third party.

  • "In the Coinjoin case, you have to trust the third parties to not log, to perform the mixing" This is simply untrue. Sure, you can implement it using a meeting place server, but that isn't inherent to coinjoin. – Gmaxwell Jul 16 at 20:40
  • OK, I know this is the case with Coinjoin as implemented by Darkcoin, but if that is not inherent in Coinjoin itself, feel free to reply to the question and I'll vote it up. – user36303 Jul 16 at 23:01
  • Yes, Darkcoin is basically an outright scam. It calls what it does coinjoin basically as some fraudulent marketing to exploit excitement from the Bitcoin space. – Gmaxwell Jul 18 at 0:38

Ring Signatures provide mixing on-chain.

CoinJoin requires you to trust the operator of the service.

Ring Sigs provide a higher level of privacy since the mixing is baked into the protocol.

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.