[ANN] ChipMixer.com - Bitcoin mixer / Bitcoin tumbler - mixing reinvented

[jackg]

And assume that someone wants to mix 0.1 BTC by receiving a hundred of 0.001 BTC chips. How will they refill those 0.001 chips without looking suspicious? Will they split some of the 0.002 and some of the 0.004? Would it be better if they split from the deposited ones?

I just don't understand how you know when it's the perfect time to create new chips.

Based on chipmixer's response times, they likely only refill chips every day at most.

There are specific chips they often like to split into smaller ones too and it's possible there's an algorithm running thst does this task (that the admin can just look over, eg dumping the raw output so it can be imported into a wallet).

Mixers work by having many users use them at once so one user is harder to trace. It's why the recommendation for privacy from chipmixer themselves is about a week (before moving funds out of mixed addresses or vouchers). Based on the support queries we have here, there are lots of people mixing 0.1btc+ - even if that was just an example - so it should be quite difficult to trace (especially if splitting is used or other  strategies like merging vouchers).

[LoyceV]

Let's say that they (ChipMixer) have the following funded addresses before they announce their service:

• 100 x 0.001 BTC

And assume that someone wants to mix 0.1 BTC by receiving a hundred of 0.001 BTC chips.

It's not good for privacy to exhaust the mixer's stash all by yourself. Luckily, for most real scenarios that won't happen.

How will they refill those 0.001 chips without looking suspicious? Will they split some of the 0.002 and some of the 0.004? Would it be better if they split from the deposited ones?

As far as I know, deposits are all split into chips again.

I conclude that there's no reason to mix more than 1 BTC using 0.512 or 0.256 chips, but rather hundreds of 0.001 & 0.002 chips unless you put the transaction fees above your privacy. It's much easier for a chain analysis company to search among 100-500 addresses than from hundreds of thousands.

Even "just" 100 addresses is still a lot if they have no idea which one they're looking for. But even better is that you don't need to mix your full input into chips instantly. You can withdraw 2 chips and keep the rest as a voucher, or even add an older voucher to get a chip larger than your last deposit.

Does that mean that you already have 0.5 & 1 BTC chips or that you'll split your weird looking 1.024 & 0.512 to 1 and 0.5? If it's the latter, isn't is meaningless?

It's the former: "round" chip amounts are also available already.

If you knew that I wanted to mix within a certain chronological period, you could exclude lots of transactions to detect who's the mixer.

How would "they" know you want to mix funds within a certain time?
Here's an example of how to obtain maximum privacy:

due to my intent to expose the blockchain data from this transaction, I decided to use an address from ChipMixer.  The address was obtained using ChipMixer voucher codes that I set aside for this potential purpose in November.  I always keep a moderate amount of money in Chip vouchers, just in case I need to do something bad for my privacy.  The money for these vouchers may have been deposited by me anytime in about the past three or four years; thus, any blockchain observer who identifies Chip inputs will not find it feasible to guess which were mine.

I just don't understand how you know when it's the perfect time to create new chips.

I would expect they use random times. And because "chips" can be created by anyone who sends funds to new addresses with value 0.001 (or 2^N times more) each, you can't be sure where it came from just from observing blockchain evidence.

[Quickseller]

This service is different than the rest due to this chip feature, which is, essentially, funds deposited prior your decision to mix coins. This means that it's time which makes it hard to trace. If you knew that I wanted to mix within a certain chronological period, you could exclude lots of transactions to detect who's the mixer.

I just don't understand how you know when it's the perfect time to create new chips.

When someone deposits bitcoin to their service, they must withdraw within a certain time by obtaining a private key for the various chips they have. Once a private key has been given to a user, CM knows that chip is no longer available and can update their database. When someone withdraws a chip, they will not necessarily spend the UTXO immidiately.

CM can periodically create new chips in a number that is approximately equal to the amount of chips that have been withdrawn. They can also estimate demand for their chips based on current account balances, and use their profits to create additional chips of certain sizes.

Generally speaking, it will never be a secret that a particular UTXO is from a particular mixer. Blockchain analysis companies will use mixers to trace that mixer's UTXO set.

From the looks of it, chips do not stay on CM for very long. One tx that CM used to create chips was 9146153f9c90075d781c3ac798472648f36e9849069a57e26206b9ca40e86e8f (12/27/2020) and the first output address was 1Mte55HMcubh11MNfKNk7C6mXjWnHj7vX It looks like whoever received this chip also received several other chips:
17c5d8ZpsEthDRaZqsCryM5kHqy1Vbc3cq ‎0.03200000 BTC (1/30/21)
14b47PAmGKsEGrvoZ9LpQdSvQbdKQ6QafJ 0.00200000 BTC (1/26/21)
157jeJakzkK18sayYsyfxKCGa8U1zrmPnb ‎0.01600000 BTC (1/31/21)
19xFcK3CLkUEBAC5PTfNHQN2rcEueFBexu 0.00200000 BTC (1/25/21)
1NQHAzip6EA3hBFjKPKgZTsvuKQmAW2pfC 0.00200000 BTC (1/27/21)
1Edu9FAbZXCFq3KXM5jgd4p2J1A1pSn9ci ‎0.01060600 BTC (1/7/21)
15GMbRgb63mYxBosA1CsKbTir9cNTDggjr 0.00008700 BTC (1/30/21)
16WgyvtAECWtDw4PpEqTQD8JYZ8y73pAyt 0.00800000 BTC (1/27/21)

The transaction that spent all of the above chips 186c9c1f6f6cd7b15a81c5836852fc3206e441583902adda18ad7a51242afe9c was confirmed 2/2/21. Whoever received the above chips cannot have received them prior to their funding date (noted above), nor after when they were spent (2/2/21). It is possible this person received chips from CM over time. I would say that the above transaction suggests CM holds chips for somewhere between 2 and 8 days before giving them to a customer.

So CM is creating new chips at a rate of at least once per week. Again, you should not expect the fact that you have a UTXO from CM to be a secret. Each of the above chips was funded with a transaction with exactly 20 outputs, all of which are exactly of the same amount (there is no change address).

[EustormBit]

...
Nevermind, was an electrum error

[ChipMixer]

what is the current state with v2 vouchers?

v2 version says they're valid on v3
v3 version says "Old vouchers will be available at Segwit version after few days"

v3 version message is old. It should be removed.
If your voucher does not work - contact support.

[WreckedAPie]

The FAQ states you "cannot withdraw small chips" but I can find nowhere that defines what a "small chip" is. What is the minimum withdraw size?

[SFR10]

The FAQ states you "cannot withdraw small chips" but I can find nowhere that defines what a "small chip" is. What is the minimum withdraw size?

It's actually listed at the very top of the exact same page ^{[under the "How does deposit work?" part]} and it's 0.001BTC:

• Minimum deposit is 0.001 BTC - lowest chip size. If you deposit less then you have to deposit missing amount to receive a chip.
  Second minimum deposit is 0.002 BTC. If you deposit between 0.001 and 0.002 BTC you will receive only 1 mBTC chip and rest will be autodonated.

  
  
• Update:
  I forgot that's also listed on the latter part of that page:
  
  

  • What will happen if I send less than lowest chip?
    Since we don't have chips lower than 0.001 BTC, your deposit will be treated as donation.

[WreckedAPie]

Let me ask it a different way, maybe it's just bad English in the faq. Are you able to withdraw the 1 mBTC chips? What about the 2 mBTC chips?

The website implies you cannot. "Instead of withdrawing small chip - we issue a voucher for that amount. You can redeem old voucher to merge two small chips into one bigger and withdraw big one." The smallest chip is 1 mBTC so this implies you cannot withdraw them but would need to combine them into a larger chip for withdraw.

[DireWolfM14]

Let me ask it a different way, maybe it's just bad English in the faq. Are you able to withdraw the 1 mBTC chips?

The website implies you cannot. "Instead of withdrawing small chip - we issue a voucher for that amount. You can redeem old voucher to merge two small chips into one bigger and withdraw big one." The smallest chip is 1 mBTC so this implies you cannot withdraw them but would need to combine them into a larger chip for withdraw.

Yes, you can withdraw 0.001BTC, but that's the smallest amount you can withdraw.  If you send 0.0025BTC to your mixing address you will be able to withdraw one chip for 0.002BTC, or two chips for 0.001BTC.  The 0.0005BTC will be donated.  If you send 0.0019BTC, you will only be able to withdraw 0.001BTC.  

For additional privacy it's not recommended to send multiple transactions to the same mixing address.  If you do however, you will not be able to combine the dust, it will be donated.  For example sending one transaction for 0.0016, and another for 0.0014 to the same mixing address will allow you to withdraw 0.002BTC.

[LoyceV]

Are you able to withdraw the 1 mBTC chips?

Yes.

What about the 2 mBTC chips?

You can withdraw those too.

The website implies you cannot. "Instead of withdrawing small chip - we issue a voucher for that amount. You can redeem old voucher to merge two small chips into one bigger and withdraw big one." The smallest chip is 1 mBTC so this implies you cannot withdraw them but would need to combine them into a larger chip for withdraw.

This is (still) in the FAQ indeed:

I assume this is (very) outdated now, and left over when fees were very high years ago.

[james3441]

Is it possible allowed to send multiple transactions to deposit address generated by chipmixer? Or should it be one transaction?

[BlackHatCoiner]

Is it possible allowed to send multiple transactions to deposit address generated by chipmixer? Or should it be one transaction?

I suspect it'll just check for the confirmation of the first transaction. If they aren't included in the same block, it may just pass the second. However, it is nowhere stated that you have to send your amount in one transaction. There's no answer in FAQ, so only @ChipMixer can enlighten us.

The real question is:  Why do you want to send multiple transactions funding the same ChipMixer address? Why not redoing the procedure with a new deposit address for the second transaction? For the sake of your privacy you shouldn't reuse addresses whether they're yours or not.

[LoyceV]

Is it possible allowed to send multiple transactions to deposit address generated by chipmixer?

Yes.

Or should it be one transaction?

No. But it's better for privacy to deposit to different sessions, and get a voucher to combine an your old session with your new session.

There's no answer in FAQ

It's in there, although slightly hidden:

Since we don't have chips lower than 0.001 BTC, your deposit will be treated as donation. Be aware that if you send 0.0015 BTC, you will receive one 0.001 BTC chip. Sending 0.0015 BTC twice will result in two 0.001 BTC chips.

[o_e_l_e_o]

It's in there, although slightly hidden:

Since we don't have chips lower than 0.001 BTC, your deposit will be treated as donation. Be aware that if you send 0.0015 BTC, you will receive one 0.001 BTC chip. Sending 0.0015 BTC twice will result in two 0.001 BTC chips.

When did this change? It used to be the case that sending 0.0015 BTC twice would result in three 0.001 chips.

[LoyceV]

When did this change?

I don't know, I just found it in the FAQ a while ago.

It used to be the case that sending 0.0015 BTC twice would result in three 0.001 chips.

I remember reading that too earlier.

[BlackHatCoiner]

True. It seems their policy changed between November 2020 and August 2021 without notice.

[james3441]

Is it possible allowed to send multiple transactions to deposit address generated by chipmixer?

Yes.

Or should it be one transaction?

Thank you

Yes, i'm aware that this decreases privacy. I'd be great if you could generate multiple deposit addresses during same chipmixer session.

I also ran blockchain study on spending  chipmixer transactions and there are two interesting things i noticed:
- Most people, like 95%+ are combining the chips while withdrawing them. They do not withdraw/spend each chip to separate addresses.
- The 0.512 and bigger chips have very few spending transactions. The difference is very significant significant. 90% of spending transactions involve smaller chips

Data from 5-6 days of blockchain transactions.
Number of spending transactions involving given chip size

0.032 337
0.016 676
0.064 200
0.256 67
0.128 94
0.512 39
1.024 22
2.048 21

Based on these numbers, does using bigger chips due to fewer transactions seen on blockchain, have any negative impact on privacy?

[LoyceV]

I'd be great if you could generate multiple deposit addresses during same chipmixer session.

Making several deposits to different addresses in a short amount of time still reduces privacy. That's why ChipMixer uses vouchers: you can keep them for a long time to make it much more difficult to link your individual inputs.

I also ran blockchain study on spending  chipmixer transactions

Can you share your findings?

- Most people, like 95%+ are combining the chips while withdrawing them. They do not withdraw/spend each chip to separate addresses.

That makes sense, to a certain extent. If you have to pay something that can't be paid from one chip, you add another one. So if you have 12 chips and need 3, you only use 3 and leave the remaining 9 untouched.

Based on these numbers, does using bigger chips due to fewer transactions seen on blockchain, have any negative impact on privacy?

It's hard to say: If you deposit exactly 0.512 BTC, get one chip, and spend it the next day, it's possible to link a list of possible inputs to possible outputs. But you could just have well deposited a much larger amount, or several smaller amounts (through the use of vouchers). You can also have months or even years between creating and redeeming the voucher. An observer can guess and make assumptions, but without additional information they can't know for sure which input belongs to which output.

[Quickseller]

Based on these numbers, does using bigger chips due to fewer transactions seen on blockchain, have any negative impact on privacy?

I would argue that using a bigger chip has a positive impact on privacy, in some situations.

If you spend two chips of equal value, someone looking would know that you sent the chip value to CM on or before each chip was created. With a single, larger chip, someone looking would know you sent the chip value on or before the date the larger chip was created.

If someone knows all transactions going to CM, the list of transactions that meet the criteria of using two small chips is going to be smaller than using a single, larger chip.

The caveat is using a single chip that is larger than necessary. If you use a very large chip that results in a large change amount, it may benefit your privacy to rather use several smaller chips, depending on the circumstances. 

[NeuroticFish]

Based on these numbers, does using bigger chips due to fewer transactions seen on blockchain, have any negative impact on privacy?

Clearly there will always be more smaller transactions of a certain size than bigger transactions.
But you can easily deposit a big value and withdraw a number of smaller chips.
And you can easily deposit a non-standard value so it's not seen as a deposit to CM, but of course, this means that you also make a donation.