A Monero contributor/developer for a few years now ... ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Tuesday, September 8, 2020 10:06 PM, <jamesd@echeque.com> wrote:
On 2020-09-01 11:31, jim bell wrote:
https://decrypt.co/40284/us-homeland-security-can-now-track-privacy-crypto-m... Jim Bell's comment: I don't know if this is true, but true or not, we need to learn the truth. Jim Bell | | Virus-free. www.avast.com |
I have examined Monero's security.
I did not find a way to break it, but it failed to inspire me with confidence.
There are lots of cryptographers vastly better than I am, but they tend to suffer from the mighty unbreakable fortress wall syndrome. They build crypto that is utterly unbreakable against the threat as defined, and all the ways around their unbreakable wall are declared to be out of scope.
No actual critique here, some vague accusation of ivory tower engineering.
And there are lots of cryptographers, me being one of them, who are aware of the fact that you need walls on all sides, but are apt to screw up the crypto. Monero struck me as being of even less than my own regrettable level of cryptographic competence, (I would not have fucked up over non prime order elliptic points)
I'm going to assume that you are not god, and are in fact infallible. Its worth mentioning that the original cryptonote authors were aware of the twist issues (or blindly/luckily followed DJB's advice) as the codebase has mul8 (the cofactor) in two key areas since the first commit. These authors came up with an entirely new ring-signature design - it was not as simple as "using academic literature" - the technique requires one-time use stealth addresses. And the stealth addresses _may_ have been the design of these same authors (its ambiguous whether "ByteCoin" on bitcointalk is related to coin with the same name). The person who wrote the bulk of the ring-CT code (not associated with the original cryptonote developers) was almost certainly aware of cofactor issues. This person had to adapt the "confidential-transactions" concept to work with Monero ring-signatures. I doubt you can claim more competence than this person, if any. The problem is some operations do not require a sub-group check or cofactor multiply, and either mitigation strategy uses non-trivial number of CPU cycles.
and somewhat less than my level of awareness of the need for walls to properly link up with each other.
The problem with Monaro, is that though it avoids the direct linking of transactions that bitcoin suffers from, it leaks a whole lot of data about networks of people transacting with each other, and I suspect that some of the time, the data that it does leak is sufficient to make a pretty good guess of what is going on behind the mighty fortress walls of cryptography, that sometimes it is bulletproof, and sometimes the bullets get through.
The problem is no worse than Bitcoin - did you intend to promote Zcash here? There's some negatives to that project that can be found via websearch, but the z-address transactions are (assuming no bugs or math errors) not leaking the information you describe.
I don't think anyone has broken it - I certainly could not - but I expect that the adversaries are making efficient use of what it does leak - that they can find interesting information in what is out of scope of its security model.
I favor Wasabi wallet, which mingles your bitcoins with those of a large number of other people.
Wasabi is not an improvement over Monero, there is far more information leakage. I can't even think of a single privacy related benefit to Wasabi over Monero transaction constructions off-hand. Every transaction has a publicly visible amount, which aids in tracing "through" the mixing process - outputs are frequently broken into fixed sized-amounts, mixed, then re-assembled into nearly the same size as the original output. Also, every output in a "mix" operation is **definitely** spent, where in Monero an output in a ring-signature is _possibly_ spent. This makes tracking a bit more challenging because an output can appear any number of times as an input. The technique by Monero is also non-interactive, so there isn't any IP related data leakage to a mixing server. Every Monero transaction requires the ring-signature construction, so they do not "stand out" like Wasabi transactions. If this "flipped" to where Wasabi style is the norm, then Bitcoin transaction volume is massively increased, narrowing (or passing) the gap to the larger Monero transactions. The code for auditing the supply still remains more simple, but I cannot think of a single benefit to privacy.
The Lightning network solves the problem that bitcoin has of transaction linkability, but you then have the correspondence banking problem, that too many "trusted" intermediaries know who is transacting with whom.
There is a flaw in the human user interface of the Lightning network's system of trust. We need a Lightning network that has less need for trust, and a human interface that is more human, so you know whom you are trusting.
Lee