

Counterparty (XCP), first trust-free decentralized asset exchange, is now live - spiderbro
http://blockscan.com/order_book.aspx
Here are some links to get started:&lt;p&gt;Block explorer: http:&#x2F;&#x2F;blockscan.com&#x2F;&lt;p&gt;Official site (under construction) https:&#x2F;&#x2F;counterparty.co&#x2F;&lt;p&gt;Installation instructions: http:&#x2F;&#x2F;counterpartyd-build.readthedocs.org&#x2F;en&#x2F;latest&#x2F;&lt;p&gt;Github: https:&#x2F;&#x2F;github.com&#x2F;PhantomPhreak&#x2F;counterpartyd
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spiderbro
Here are some links to get started:

Block explorer: [http://blockscan.com/](http://blockscan.com/)

Official site (under construction)
[https://counterparty.co/](https://counterparty.co/)

Installation instructions: [http://counterpartyd-
build.readthedocs.org/en/latest/](http://counterpartyd-
build.readthedocs.org/en/latest/)

Github:
[https://github.com/PhantomPhreak/counterpartyd](https://github.com/PhantomPhreak/counterpartyd)

Discussion thread:
[https://bitcointalk.org/index.php?topic=395761.0](https://bitcointalk.org/index.php?topic=395761.0)

~~~
pyalot2
So thing is this, you're using proof of burn and/or some derivative of proof
of stake or whatever.

Thing is what proof of * you use don't matter. You're not in control of the
chain, and anybody can just spam the bitcoin blockchain with fraudulent
transactions (double spends, etc.)

And the only way for anybody want to accept any of those assets, would be to
calculate the probability of having a real asset in hand from the entire
blockchain history that this amount derives off of.

So, very sorry to say that, but, this'll crash&burn. That's just how it is if
you forgoe the iron guarantees of proof of work.

~~~
spiderbro
Could you give an example of a double spend attack on XCP?

From what I understand, XCP transactions guarantee atomicity and funds are
swept from addresses to fund any bets/orders immediately. The risk of double-
spending XCP is the same as the risk of double-spending BTC as XCP relies on
bitcoin's proof of work.

Please correct me if I'm wrong.

~~~
pyalot2
XCP would rely on the blockchain, and therefore it's atomic transactions are
executed. However, the ones putting the transactions in the chain, are not XCP
miners. They're bitcoin miners, they don't care what extra information you
attach. And by extension, they don't care if they violate some rule in your
protocol.

This basically means that XCP-looking transactions will appear in the
blockchain, however, they will be invalid, because by the rules of XCP their
outputs would already be spent.

In Bitcoin this is an invalid transaction, and it never enters the public
ledger. This important because, it allows you to shortcut the path to figure
out if an address has unspent outputs. Figuring out quickly if an address has
unspent outputs or not is important for miners (they need to produce valid
blocks), and it's important for participants to transactions, because it means
the recepient can quickly verify that the sender is intending to make the
transaction, and that a transaction, sufficiently confirmed, is not double
spent. The recepient relies on the work of everybody who produced a block. And
in turn, everybody who produces a block relies on the work of everybody before
AND on the work of everybody after (who bases their block on his).

This is what I mean by iron-clad guarantee against a double spend.

But if nobody can reject an invalid TX for XCP, that means verifying that
something has unspent outputs is an extremely expensive task. And the longer
transactions go on, the more expensive this task becomes. And nobody can put
in some kind of "block" that could be rejected by others to "proove" that some
balances on addresses are now valid up to that point.

This means that in a short time, XCP will become unusable for everybody as the
XCP-TX spam rises and everybody is checking the entire bitcoin blockchain over
and over and over for XCP-looking TXes to figure out if the coin he thinks he
got, aren't actually double spends.

~~~
spiderbro
Ok I think I understand your point that XCP-invalid-TX spam cannot be filtered
at the point of origin like invalid BTC transactions and a motivated attacker
could spam the network to make it extremely slow to use XCP.

I think this is a valid concern, even if somewhat mitigated by the 0.0001 BTC
transaction fee. I'll post this to the BTCTalk thread and see if someone
smarter than me has an idea to defend against it.

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dmix
Can someone "explain like I'm 5" what some of the use cases are for this
service? I've been following bitcoin and distributed services for a while and
I'm still confused (or lazy).

The website copy is extremely abstract and non-specific. It's in need of a
copywriter.

~~~
spiderbro
Here are a couple of uses cases off the top of my head. This is by no means
comprehensive.

* The ability to issue shares in your company/startup and have them be traded from Day 1. Unlike BTCT/BitFunder/Havelock, Counterparty is a P2P protocol and cannot be shut down by regulatory agencies. Kind of like BitTorrent.

* The ability to trade XCP for Bitcoin and vice versa without relying on any fallible counterparty. There is no centralized exchange to steal money from you or fail like MtGox. There is no escrow required to trade with peers because Counterparty guarantees atomicity of transactions.

* The ability to place a variety of different bets. Currently the protocol has support for simple contracts-for-difference (CFDs) and binary Equal/NotEqual bets. Why is this useful? You could for example hedge your exchange rate risk completely by being short a XCP/USD contract. This allows you to hold your wealth in cryptocurrency but have no exchange rate risk. Another use case is sports betting. There was a friendly bet on the Super Bowl, for example.

------
neals
You might need to read this though (I sure did, still don't really get it)

[https://counterparty.co/about/](https://counterparty.co/about/)

~~~
cazzoduro
2 virtual objects + secure peer to peer exchange of those objects.

what is so hard about getting that...

