So now that blockchain supports CoinJoin, what pitfalls should we be aware of?

[_mr_e]

So I have a basic understanding of what CoinJoin is doing however I am wondering if there is a FAQ out there on how to use it safely without accidently leaking info?
Is it as secure as coin mixing? Why would I pay 0.5% for blockchains mixing service when CoinJoin is free? What limitations does it have? How easy is it to leak data that would lead to uncovering your mixing?
I think we need something that answers these questions for people so they are aware of what they are doing because I find CoinJoin somewhat hard to understand what's exactly going on under the covers.

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[piuk]

So I have a basic understanding of what CoinJoin is doing however I am wondering if there is a FAQ out there on how to use it safely without accidently leaking info?

The website and FAQs are not available yet, so as a quick summary:

Coinjoin is a method of coin mixing which requires less trust in the mixing service. The coinjoin service available on blockchain.info is known as "Shared Coin" and is a separate entity to blockchain.info hosted at https://sharedcoin.com. Shared coin hosts a server which acts as a meeting point for multiple people to join together in a single transaction. Having multiple people in a transaction improves privacy by making transactions more difficult to analyse. The important distinction between traditional mixing services is the server cannot confiscate or steal your coins.

A sharedcoin transaction will look something like this: https://blockchain.info/tx/e4abb15310348edc606e597effc81697bfce4b6de7598347f17c2befd4febf3b (picked at random). As you can see multiple inputs and outputs make the determining the actual sender and receiver more difficult.

The server does not need to keep any logs and transactions are only kept in memory for a short time. However If the server was compromised or under subpoena it could be force to keep logs and deanonymize the users. If this were to happen although you haven't gained any privacy you haven't lost any either. For this reason, especially for those desiring strong anonymity, it will likely be wise to rely on multiple different coinjoin implementations (even if using a p2p system). Infiltrating one system is much easier than infiltrating multiple systems and correlating everything together. If enough people use coinjoin and it is integrated into multiple different clients the privacy of everyone in the bitcoin network improves.

How to use it safely without accidently leaking info?

- Tor can prevent leaking of information through your ip address.

- Sending coins to or from tagged addresses reduces privacy.

- When creating a shared coin transaction your browser generates a number or temporary/intermediate addresses. The balance of these addresses is not checked on blockchain.info itself unless the "Recover Intermediate Addresses" button is used. Looking up the balance of these addresses is an information leak as if blockchain.info was keep logs it would show you had an interest in these addresses. So don't use the "Recover Intermediate Addresses" tool unless there has been an error with a transaction.

What limitations does it have?

Coinjoin can never completely sever the link between the input and destination address, there will always be a connection between them, it is just more difficult to analyse.

Why would I pay 0.5% for blockchains mixing service when CoinJoin is free?

Shared send can handle larger amounts more effectively, it also guarantees 0% taint which coinjoin can never do. Shared send will most likely be depreciated in time but at the moment there are use cases for both services.

[sangaman]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

[piuk]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

[Nemesis]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

where is the announcement about this?

I would like to try the service

Edit: i just try a fraction btc amount. The transaction has been confirmed but when do i expect to receive my fund?

[sangaman]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

Fantastic! Thank you so much for leading the way on this.

My last question is when will this be available on the Firefox extension? I prefer to use that for security reasons, although I don't mind using the website for the Coinjoin transactions until the browser extensions are updated.

[Nemesis]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

Fantastic! Thank you so much for leading the way on this.

My last question is when will this be available on the Firefox extension? I prefer to use that for security reasons, although I don't mind using the website for the Coinjoin transactions until the browser extensions are updated.

The fee still applies. I just tried it.

Boo Hoo

[redphlegm]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

Fantastic! Thank you so much for leading the way on this.

My last question is when will this be available on the Firefox extension? I prefer to use that for security reasons, although I don't mind using the website for the Coinjoin transactions until the browser extensions are updated.

The fee still applies. I just tried it.

Boo Hoo

I think you tried the SharedSend feature, which is different from CoinJoin. I can't actually find CoinJoin to give it a try.

Any insight from those who know how to use it? Maybe I'm blind but I simply can't find how to use it.

[Nemesis]

Will Blockchain be offering any free or very low fee CoinJoin transaction service? I can't really justify ~0.5% but I'd like to start using it. If we want to get regular users who aren't trying to hide criminal activity or tainted coins to use CoinJoin, the cost will need to be lower since the perceived benefit to regular users is lower as well.

The 0.5% fee was removed recently and the service is now free (excluding bitcoin network fee).

Fantastic! Thank you so much for leading the way on this.

My last question is when will this be available on the Firefox extension? I prefer to use that for security reasons, although I don't mind using the website for the Coinjoin transactions until the browser extensions are updated.

The fee still applies. I just tried it.

Boo Hoo

I think you tried the SharedSend feature, which is different from CoinJoin. I can't actually find CoinJoin to give it a try.

Any insight from those who know how to use it? Maybe I'm blind but I simply can't find how to use it.

Nope i used what he said https://sharedcoin.com. Not sharedsend feature on blockchain.info.

I hate ppl say one thing then never come back to verify. The site still say the free. No official announcement.... just an employee's claim.

[piuk]

Nope i used what he said https://sharedcoin.com. Not sharedsend feature on blockchain.info.

I hate ppl say one thing then never come back to verify. The site still say the free. No official announcement.... just an employee's claim.

https://twitter.com/blockchain/status/402224010492006400

There is a fixed network fee of 0.0005 BTC per repetition. The network fee is larger than regular transactions because the transactions are  larger. Excluding from the network fee there is no other fees and no percentage fee.

[Nemesis]

Nope i used what he said https://sharedcoin.com. Not sharedsend feature on blockchain.info.

I hate ppl say one thing then never come back to verify. The site still say the free. No official announcement.... just an employee's claim.

https://twitter.com/blockchain/status/402224010492006400

There is a fixed network fee of 0.0005 BTC per repetition. The network fee is larger than regular transactions because the transactions are  larger. Excluding from the network fee there is no other fees and no percentage fee.

Really? I sent 1.3043 and received  1.2973 which is result of exactly 0.5% + 0.0005 fee. U must think i cant do math when i said fees still applied.

Explain that?

[sangaman]

Nope i used what he said https://sharedcoin.com. Not sharedsend feature on blockchain.info.

I hate ppl say one thing then never come back to verify. The site still say the free. No official announcement.... just an employee's claim.

https://twitter.com/blockchain/status/402224010492006400

There is a fixed network fee of 0.0005 BTC per repetition. The network fee is larger than regular transactions because the transactions are  larger. Excluding from the network fee there is no other fees and no percentage fee.

Really? I sent 1.3043 and received  1.2973 which is result of exactly 0.5% + 0.0005 fee. U must think i cant do math when i said fees still applied.

Explain that?

Did you use sharedcoin.com or the blockchain.info wallet to make the transaction?

[Nemesis]

Nope i used what he said https://sharedcoin.com. Not sharedsend feature on blockchain.info.

I hate ppl say one thing then never come back to verify. The site still say the free. No official announcement.... just an employee's claim.

https://twitter.com/blockchain/status/402224010492006400

There is a fixed network fee of 0.0005 BTC per repetition. The network fee is larger than regular transactions because the transactions are  larger. Excluding from the network fee there is no other fees and no percentage fee.

Really? I sent 1.3043 and received  1.2973 which is result of exactly 0.5% + 0.0005 fee. U must think i cant do math when i said fees still applied.

Explain that?

Did you use sharedcoin.com or the blockchain.info wallet to make the transaction?

Sharedcoin.com as i mentioned above.

[sangaman]

OK, I think you should use the "shared coin" send feature from within the blockchain.info wallet to avoid the 0.5% fee. I haven't tried it yet personally but it lists the fee as 0% regardless of the number of repetitions.

[piuk]

Sharedcoin.com as i mentioned above.

Sorry my mistake, don't use sharedcoin.com yet.

You need a blockchain.info wallet: Login -> Send Money -> Shared Coin

PM me or post you address and I will send you refund of the fee.

[Nemesis]

Sharedcoin.com as i mentioned above.

Sorry my mistake, don't use sharedcoin.com yet.

You need a blockchain.info wallet: Login -> Send Money -> Shared Coin

PM me or post you address and I will send you refund of the fee.

Ah .... so whats the difference between sharedsend and sharedcoin?

The name that make its confusing so i thought sharedsend is sharedcoin.

When does the no fee end?

[piuk]

Ah .... so whats the difference between sharedsend and sharedcoin?

With Shared Send you send blockchain.info your coins and blockchain.info will send you back different coins.

With Shared Coin you combine your transaction with other people. Unlike shared send the coins never leave your control.

When does the no fee end?

Indefinitely. To be effective it needs to be used by as many people as possible without fees deterring users.

[Nemesis]

Ah .... so whats the difference between sharedsend and sharedcoin?

With Shared Send you send blockchain.info your coins and blockchain.info will send you back different coins.

With Shared Coin you combine your transaction with other people. Unlike shared send the coins never leave your control.

When does the no fee end?

Indefinitely. To be effective it needs to be used by as many people as possible without fees deterring users.

So sharedsend does not give you a link between the destination and input address?


Thanks for such service, now i wonder why we need sharedcoin.com

[sangaman]

Can we have an option to specify change addresses for shared coin transactions? And an option to send to multiple addresses (similar to how is possible in custom send)?

Also, will the shared coin feature be coming to the browser extensions and mobile apps in the foreseeable future? Thanks a bunch.

[piuk]

So sharedsend does not give you a link between the destination and input address?

Correct.

Thanks for such service, now i wonder why we need sharedcoin.com

Soon there will be a purpose to sharedcoin.com, at the moment it is just a placeholder.

Can we have an option to specify change addresses for shared coin transactions? And an option to send to multiple addresses (similar to how is possible in custom send)?

Also, will the shared coin feature be coming to the browser extensions and mobile apps in the foreseeable future? Thanks a bunch.

Good suggestions, we have plans to implement them all.

Lots of improvements to error handling and recovery made today, so if you have experienced any errors previously please give it another try now.