How much is public?

[bitcoinrocks]

How much info about our BTC is public?  If someone knows your BTC address, do they know how many BTC you have?  Someone said that they know how many BTC you "had" but I can't seem to conceptualize this.  How does it work?

[Aswan]

The Database of bitcoin is decentralized and therefore public. Every transaction can be seen by everyone else. However, since a bitcoin address does not have your name in it, it is up to you to let people know the address belongs to you. If one of your addresses gets linked to you, then yes, people can see how many BTC you have / had. However, once you transfer it to another address nobody can know for sure if you still own that new address or if you sent the coins to someone else.

The key to anonymous bitcoin usage is to not link your address to your name, which is not that easy.

[DannyHamilton]

How much info about our BTC is public?  If someone knows your BTC address, do they know how many BTC you have?  Someone said that they know how many BTC you "had" but I can't seem to conceptualize this.  How does it work?

You can have multiple BTC addresses.  You can have as many BTC addresses as you want.  I suggest using a new BTC address for EVERY transaction.

If someone knows one of your BTC addresses, then they can know exactly how many BTC are controlled by that address.  They can know the date and value of every transaction that ever has been or ever will be received at that BTC address, and they can know the date and value of transactions that were (or in the future are) funded by the bitcoins that had been received at that address.

They may also be able to infer other addresses that you control and gain similar insight into those addresses.

[Shallow]

Even though people can see your address they can't do anything with it without the private key.

[Xatian]

You can have multiple BTC addresses.  You can have as many BTC addresses as you want.  I suggest using a new BTC address for EVERY transaction.

I (everyone) always read that argument, but think about it ... that is pretty problematic.
Assume BTCs have conquered the world and every shop accepts them, so you can go out and pay for stuff.
How do you think using new addresses improves your anonymity?
In order to spend coins from the new address (the one you just made to improve your anonymity) you need to send coins there ... meaning I know where these coins came from ... meaning if I know one of your addresses in time and with afford I can track you ... every single transaction you did or will do in the future.
Pretty scary don't you think?

[Aswan]

You can have multiple BTC addresses.  You can have as many BTC addresses as you want.  I suggest using a new BTC address for EVERY transaction.

I (everyone) always read that argument, but think about it ... that is pretty problematic.
Assume BTCs have conquered the world and every shop accepts them, so you can go out and pay for stuff.
How do you think using new addresses improves your anonymity?
In order to spend coins from the new address (the one you just made to improve your anonymity) you need to send coins there ... meaning I know where these coins came from ... meaning if I know one of your addresses in time and with afford I can track you ... every single transaction you did or will do in the future.
Pretty scary don't you think?

That is where Coin Mixing Services come into play.

[Dabs]

... meaning if I know one of your addresses in time and with afford I can track you ... every single transaction you did or will do in the future.

You don't know that the previous address was owned by the same person, and you don't know if the new address(es) are also from the same person or from different people.

You could make a guess, but as soon as the coins go into a shared wallet, then it comes out to a different address and you just lost the trail unless you do some more investigating.

[Xatian]

Well I know that it is possible to make it harder ... But no matter I think this is pretty problematic.
I always assumed that if I own several addresses I can send my coins from any one of them at any time ... but that is not true.
Which means there is no way to do an untraceable moving of coins from A to B --> there is no cash.

Today every online bank transaction is traceable ... it is hard because you need to talk to all the banks but it is of course possible. But there is cash ... noone can trace cash-deals or gold for that matter. I know it is also hard to move a lot of cash or gold without anyone noticing it but it is possible. It is possible to do that and leave no trace. No trace at all.
In the future (with bitcoins) it is not. Its even easier to trace as I just need to ask the blockchain and not several banks, western union, moneygram and all the other money-moving-businesses.

Disclaimer:
I like Bitcoin and I have supported them since a long time ... I am just saying :-)

[Dabs]

You have things like Zero Coin (not yet implemented) and CoinJoin, and you have 3rd party mixing services or tumblers or laundry services.

Then you have shared wallets or online wallets and exchanges.

Then you have people trading bitcoins for litecoins or other altcoins, and people trading bitcoins for cash.

If you do enough steps trading, you can dislocate the trail and it won't be on the blockchain. It will be, but no one else would know how to connect them.

[bitcoinrocks]

A 3rd party scenario would be sending coins from your address to a 3rd party and then from the 3rd party to a different address of your's?  You would have to trust the 3rd party to some degree and I suppose you would have to use Tor.  Personally I wouldn't be able to go through a process like that and feel confident in my privacy.

[Dabs]

The 3rd party mixing services gets your bitcoins, then spits out bitcoins coming from a different address with no link in the blockchain from where you originally sent the bitcoins to.

Some of these even break down the transaction into smaller pieces, so it's hard to add them all up unless you knew which addresses to watch. Since you can't know if you are not the owner of those coins, you have "laundered" your coins.

My plan is to just gather up a bunch of coins from a lot of different people, combine and send them all to one address, then send them back out to their original owners (minus the mixing fee).

The coins would still be tainted somehow, but you since you can't track an individual satoshi or even the whole amount, the outputs are hard or impossible to match up to the original inputs.

CoinJoin is an attempt to do the same thing but mix everyone's transactions into one giant transaction so everyone gets tainted rich. Blockchain.info online wallet is now attempting to do this. With their number of users, it just might work.

[Abdussamad]

TLDR; of this thread is that it is ALL public. Longer explanation follows:

9.9/10 people (yes I actually said .9 people) use one address for all their transactions. This is a fact. So all their transaction data is public knowledge.

Those who use multiple addresses can also be tracked. It just requires more work. Special algorithms may have to be crafted to do this but I bet it can be done.

Also if you use something like Electrum all your addresses are revealed to the server you connect to. The connection between your system and the server is SSL encrypted. Now we know that the NSA has broken that so all your transaction data is known to them too.

[DannyHamilton]

9.9/10 people (yes I actually said .9 people) use one address for all their transactions. This is a fact. So all their transaction data is public knowledge.

Source?

Sounds like hyperbole to me.

Those who use multiple addresses can possibly be tracked.

FTFY.

It depends on what other steps they take to protect their anonymity.

I bet it can be done.

So you're guessing?

[ChazM]

The nice thing about Bitcoin is that it uses your change addresses as well for transactions, which is something I didn't know until I tried to trace a recent transaction of mine. I had to trace back a few transactions until I found an address I recognized on one of my old transactions.

[acoindr]

How much info about our BTC is public?  If someone knows your BTC address, do they know how many BTC you have?  Someone said that they know how many BTC you "had" but I can't seem to conceptualize this.  How does it work?

The way Bitcoin works all address balances are public. This is inherently necessary because Bitcoin is trust-less and decentralized. There has to be a way for everyone to verify who has what.

This is where a lot of confusion about Bitcoin anonymity comes into play. Reading the above doesn't sound very anonymous, and it's not usually. For someone willing to do the work a lot of information can be gleaned, guessed at and inferred from analysis of the block chain.

The reason Bitcoin can be completely anonymous is because address ownership is not always tied to real world identities. With Bitcoin you only need to (mathematically) show the network you have the private key to move coins, no identity required. Therefore, if you can disassociate all of your real world identity from your virtual coin ownership you can use Bitcoin anonymously. It's possible to do this if you understand how the Internet and computers work on a technical level. There are many techniques which can be effective, and tools like Tor and coin mixing services make it fairly easy for the technically astute. Otherwise, only "pseudo" anonymity exists by default (non-obvious identity relationships).

[StevenS]

You can have multiple BTC addresses.  You can have as many BTC addresses as you want.  I suggest using a new BTC address for EVERY transaction.

...

They may also be able to infer other addresses that you control and gain similar insight into those addresses.

When you have multiple addresses, it's very difficult to manage them without keeping them together in one wallet (app). IIUC, most wallet apps will automatically combine the bitcoin from smaller balances in multiple addresses in order to pay a larger amount. Since this transaction is also public, it can link your multiple addresses.

[acoindr]

You can have multiple BTC addresses.  You can have as many BTC addresses as you want.  I suggest using a new BTC address for EVERY transaction.

...

They may also be able to infer other addresses that you control and gain similar insight into those addresses.

When you have multiple addresses, it's very difficult to manage them without keeping them together in one wallet (app)...

This may be difficult or inconvenient, but not impossible. For anyone serious about complete anonymity some usability tradeoffs might be tolerable.

IIUC, most wallet apps will automatically combine the bitcoin from smaller balances in multiple addresses in order to pay a larger amount. Since this transaction is also public, it can link your multiple addresses.

Yes, so when making an effort to be truly anonymous it's probably a good idea to use different wallets for different types of activity and keep them technically separate...

[Dabs]

ahhhh... let me just say two words: Coin Control.

[bitcoinrocks]

Aren't coin mixers the kind of thing "they" will come down hard on you for if they decide to make you a target?  At some point things like that make you more suspicious and can actually serve as evidence against you.

[davinchi]

a wallet can have many address people wont know how much actualy you have