Is PrivateSend (coinmixing) safe?

dashmeister

dashmeister

New member
I have a question about coinmixing/PrivateSend
I'm afraid it's not untracable. Its not anonymous.

And this would be a big problem!

There are two reasons:
1.
Even I make several rounds with mixing, I'm usually, always mixing my dashes with the same mixing members, which are also want to mix at the same time. I mean there are not many people use mixing every hour (sometimes 0).
Or did I understand something wrong?

Example:
I'm (A) going to mix 60 dashes in 3 rounds. I'm only concentrate here on my dirty dashes which I dont wnat have any connection anymore:

Start mixing:
A 60 -> A 10 10 10 10 10 10 10
So first mixing round is starting.
There are two members (B, C) taking part of the mixing.
B has 50 coins and C 20.
So my 6*10 goes randomly to B and C. I'm only following here my dirty dashes.

***** 1st round:
A
B 10 10 10 10 10 10
C 10

***** 2nd round:
Lets say a new member was coming to the mixing with 100 dashes. So we have 60,50,10 and 100 dashes in the pool. The 5* 10 dashes are randomly distributed between A (chance 6/17), C (1/17) and D (10/17). The same with the 1*10 dash of C

A 10 10 (So after 2 round I have back 20 of my 60 dirty coins back)
B 10
C
D 10 10 10

***** 3rd round:
For B it was the last mixing, No new member in the mixing pool. So we have only A (60), C (10) and D (100). So the 2*10 from A will go to C and D. The 3*10 from D will go (6/7) to A and (1/7) to C.
A 10 10 10
B - gone (he have one of the dirty 10)
C -
D 10 10

So after 3 round mixing I still have 50% of my dirty coins. Ths problems we have when teh coins are mixed only between a small number of people


But even there would be a huge amount of members in the mixing, there is another problem

Lets say my sister steals from me secretly 100 dashes from my phone wallet.

So she is transfering 100 dashes in a new virgin address.

Then 2 weeks later she is usecoinmixing. She thinks is clever and making 8 round. So the 100 dahes are mixed in 10*10 dahes (I make it simple here, I know there are fees and some of the dahes are split into smaller amounts. But thats not the point) and moved 8 times to difference addresses. Lets say there is no connection between the stolen dashes and the new coins (I doubt this very much, see above, but just let's assume that).

Then 6 month later she is telling me that she just donated 3 dahes to Stefan Molyneux. She did it by PrivateSend and was thinking she is safe, because its "PrivateSend".
I check the blockchain with the public address of Stefan and see that the 3 dashes are coming from a 10 dash wallet which was filed up October 11 9:30 by coinmixing (it is very easy to see in the blockchain that its mixed).
I also chan check the blockchain about my stolen dahses and I can see:

Date/Time sender amount receiver
April 3 10:12 my wallet 100 dashes thief
April 20 07:15 thief 100 dashes coinmixing

So I don't can 1000% prove that she stole my money and there is a chance from 1:1 million that this just coincidence, that the thief and she mixed her dashes in the same 2h window.
But actually, I know now (even with PrivateSend and 8 round coinmixing) that she was the thief (and that all without any analytic software).
 
You can't follow your "dirty dashes" from round to round. They are joined, there is no way to tell who received what.

Round 1 (mixing dirty coin A):
Inputs: A: 10 Dash; B: 10 Dash; C: 10 Dash
Outputs: D: 10 Dash; E: 10 Dash; F: 10 Dash

Round 2 (following D):
Inputs: D: 10 Dash; G: 10 Dash; H 10 Dash
Outputs: I: 10 Dash; J: 10 Dash; K 10 Dash

Round 2 (following E):
Inputs: E: 10 Dash; L: 10 Dash; M 10 Dash
Outputs: N: 10 Dash; O: 10 Dash; P 10 Dash

Round 2 (following F):
Inputs: F: 10 Dash; Q: 10 Dash; R 10 Dash
Outputs: S: 10 Dash; T: 10 Dash; U 10 Dash

At the end of round 2, any one of I, J, K, N, O, P, S, T or U could be the one that originally took control of your coin.
 
lynx said:
At the end of round 2, any one of I, J, K, N, O, P, S, T or U could be the one that originally took control of your coin.
Click to expand...

Yes everybody, but it coul be also MYSELF! If theer are several coins, I wil got almost for sure dirty dash back.
I dot want my coins back, which can be connectable with me.
I have no problem, if I get dirty other coins, as long there is no connection to me. But because we are coining with the same people. First round all of my coins are gone, but second round I will get them partly back
Probably I will get back at least some of my dirty coins (they are just moved over several adresses, but still the same dash and even same amount).
I need clean dashes, which nobody can trace back to myself, not dirty dashes.

If we would make only one round of mixing its maybe safer than many rounds? But then the one masternode owner, knows my secret .
 
dashmeister said:
First round all of my coins are gone, but second round I will get them partly back (...) If we would make only one round of mixing its maybe safer than many rounds? But then the one masternode owner, knows my secret .
Click to expand...
That's not how it works... for anyone exploring the blockchain, your coins are NOT "gone" in the first round, they just have a 1/3 probability to of belonging to each output party. They are never gone, and they are never back. You will always be connected to them, but so will a lot of other people. It's like used cash dollar notes that have traces of cocaine on them, they all do. That's the concept of fungibility, no coin is worth less than any other because of where they've been.

So if you wanted to make it look that that dirty coin you received is not yours, if you just mix it one round it would still look like it's yours, even if it actually went to someone else. The coins are not marked, it doesn't make a difference, you see?

PS: Take a look at a real mixing session: https://explorer.dash.org/tx/4cb97e366c1fd19c60015efe490770d660a61f63622cbd32cb242ea7f2ad4c5f
 
lynx said:
You will always be connected to them, but so will a lot of other people
Click to expand...
Yes but this is my problem. I don't want to be connected to them at all. Compared to bank notes. Its like there is my fingerprint on the banknote. Ok, there is also fingerprint of 20 other people there, but if I made a crime, I don't want my fingerprint on the banknote at all.

Can a fingerprint proof that you did a crime? Not 100% (because it could be also one of the 20 guys which fingerprint is on the note), but at least its an evidence together with others.

Like my example iny my first posting:
If my sister steal 100 dahes from my wallet, then she mix it, then one day I see a mixed dash in her wallet. If I can see that there is a connection between my stolen dah and her dahes, then I know that she stole my money, even 20 or even 100 other people also connected with the dash.
Because how are the chances that this was just coincidence, that she is innocent and just mixed her dash at the same time than thief did?
 
If that's the case, your sister will have to mix it enough and at various different times so that the dirty coins are connected to almost everyone that does mixing (maybe even to you - again), and she just happened to be one of them. It's like having tens of thousands of fingerprints on the banknote.
 
dashmeister said:
Because how are the chances that this was just coincidence, that she is innocent and just mixed her dash at the same time than thief did?
Click to expand...

There is no such thing as "the same time". Mixing happens long before spending.

dashmeister said:
but if I made a crime, I don't want my fingerprint on the banknote at all.
Click to expand...

Ever tried not being a criminal then?
If you truly did something illegal it's in society's best interest to have you caught, anyway.
With that said your concerns are invalid as lynx correctly and very succinctly explained in his last post.
 
Nobody is ever going to get implicated in a crime because the cash has passed through their wallet at some point, that applies with physical and digital cash.

Walter
 
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