Exploiting Special Properties of Bitcoin For Uses Other Than Currency

[Delia]

I believe you're describing Hashcash.

[Anonymous]

Whats the one thing humans have that is limited ? It is time...

Bitcoin can be used to solve the "tragedy of the commons" where people see something having no cost and then abuse it.

People say all the time twitter should be decentralised.
An open source twitter that allows me to pay for longer messages if I want to do so would be beneficial. Also let me filter direct messages which have a bitcoin attached and I might read them because it says to me "your time is valuable". Call it an "attention mail" or something. If people think other's time is worthless they will abuse it constantly.

Twitter direct messages are broken. The service goes down all the time because it relies on a central server.

Can bitcoin form the basis for an ethical short messaging service where people's attention is valued as it should be?

[ShadowOfHarbringer]

If BitDNS or <other programmers pet project X> becomes conjoined to Bitcoin, I am instantly selling all my BTC and leaving.

I would too.  So the exchange rate would crash.

Same here.
Merging bitcoin with some other completely unnecessary crap would be the worst idea of the century.
I would welcome a fork with open arms in such a situation.

If anybody wants to play, he should find himself a sandbox. We're doing serious buisness here, this is no place for toys.

[Local]

If BitDNS or <other programmers pet project X> becomes conjoined to Bitcoin, I am instantly selling all my BTC and leaving.

I would too.  So the exchange rate would crash.

Same here.
Merging bitcoin with some other completely unnecessary crap would be the worst idea of the century.
I would welcome a fork with open arms in such a situation.

If anybody wants to play, he should find himself a sandbox. We're doing serious buisness here, this is no place for toys.

Does a change need to be made to let this stuff in, or a change made to keep this stuff out?

Can you tell me more about why it matters if a transaction has extra meaning to someone else. How will you even tell, won't it look like a normal transaction? Only legit transactions can get in, right?

Sorry if I'm confused or missed these answers.

[jgarzik]

Merging bitcoin with some other completely unnecessary crap would be the worst idea of the century.
I would welcome a fork with open arms in such a situation.

If anybody wants to play, he should find himself a sandbox. We're doing serious buisness here, this is no place for toys.

Does a change need to be made to let this stuff in, or a change made to keep this stuff out?

Can you tell me more about why it matters if a transaction has extra meaning to someone else. How will you even tell, won't it look like a normal transaction? Only legit transactions can get in, right?

If someone wants to transmit arbitrary data, there is generally always a way.  For example, data may be encoded today in a standard transaction, probably around 32 bits per transaction, simply by specifying an amount such as "0.12345678".

However, that does not mean that we should encourage the use of additional, non-standard transaction types created for the express purpose of storing arbitrary data in the block chain.  For example, it has always been possible to tunnel the IP protocol over DNS; but that does not mean it is wise to do so.  No mainstream DNS server supports such behavior, even if the protocol itself does.

Some BitDNS proposals here describe operations such as storing DNS records themselves in the block chain, where each IP address or nameserver change would be propagated throughout the bitcoin P2P network, and be stored in the local storage of all bitcoin full-block-chain P2P clients.

[ShadowOfHarbringer]

If BitDNS or <other programmers pet project X> becomes conjoined to Bitcoin, I am instantly selling all my BTC and leaving.

I would too.  So the exchange rate would crash.

Same here.
Merging bitcoin with some other completely unnecessary crap would be the worst idea of the century.
I would welcome a fork with open arms in such a situation.

If anybody wants to play, he should find himself a sandbox. We're doing serious buisness here, this is no place for toys.

Can you tell me more about why it matters if a transaction has extra meaning to someone else. How will you even tell, won't it look like a normal transaction? Only legit transactions can get in, right?

Sorry if I'm confused or missed these answers.

My concern is putting unnecessary bloat in bitcoin transactions. Check this out:

MasterCard processes over 22 billion transactions each year, has the capacity to handle 140 million transactions per hour, with an average network response time of 140 milliseconds and with 99.99 percent reliability.

OK, so 22 billion transactions per year. That gives us ~60 milion transactions per day, ~2.5 million transactions per hour, ~41000 transactions per minute and ~695 transactions per second.

Right now, bitcoin requires about 275 bytes of transfer/storage per single transaction, which gives us 190 972 bytes of transfer/storage per second, 687 500 000 per hour, and 16 500 000 000 per day. Yeah, that is 687 MEGABYTES PER HOUR and 17 GIGABYTES PER DAY.

If bitcoin is supposed to ever become LARGE like VISA or MasterCard, it has to be prepared to handle large amounts of transactions. And putting some additional crap in transactions will make the bandwidth/storage space requirements become VERY difficult for people who want to run their own clients (and i intend to).

If you add for example only 100 bytes to each transaction (not much, right ?), then total amount of space&bandwidth will increase by almost 40%. And 17 Gigabytes per day is already enough.

[Local]

So there is no way to handle the growth? This seems like a problem whether other stuff goes in or not.

But that didn't really answer my question. Even if it is bad, how can it possibly be stopped? Aren't people talking about making normal looking transactions and interpreting them in a certain way? Are you suggesting future versions of the client should test all transactions for extra meaning and block them?

[ShadowOfHarbringer]

So there is no way to handle the growth? This seems like a problem whether other stuff goes in or not.

Yes, there is a way. Only put necessary information in the chain. Keep currency-unrelated stuff out, and it will be fine.

Even if it is bad, how can it possibly be stopped? Aren't people talking about making normal looking transactions and interpreting them in a certain way?

1. There is a mechanism already implemented to do that. Transaction fees. If there are too many transactions, per transaction fees my kick in automatically. However i don't know how does that  exactly work.
2. This cannot be completely stopped, but that is not a problem until bloat is kept out of official chain. As long as the tansactions are "standard", but hold some steganographic information in them, it's OK.

Are you suggesting future versions of the client should test all transactions for extra meaning and block them?

You overslept. That is exactly what version 0.3.18 is doing using isStandard() function. It filters out all non-currency transactions unless I am not misunderstanding something.

[jgarzik]

So there is no way to handle the growth? This seems like a problem whether other stuff goes in or not.

Transaction fees.

Whether the block chain is currency-only or currency+data, the result is the same:  transaction fees rise as overall block size increases.

More data == more expense (theoretically the block chain provides more value to more people, and is therefore more valuable)

[FreeMoney]

You overslept. That is exactly what version 0.3.18 is doing using isStandard() function. It filters out all non-currency transactions unless I am not misunderstanding something.

It doesn't stop this:

You don't get it.  It's not steganography at all.  You don't really send any data to the network.  It is the same amount of "data" injected, whether you timestamp a "hello world" or a 1Go tarball !

It seems that I have to make an example to make it really clear.

So, I'm going to time stamp the tarball version of bitcoin, version 0.3.19.

First, I make a GPG signature of it :

$ gpg -s bitcoin-0.3.19.tar.gz

This creates a bitcoin-0.3.19.tar.gz.gpg file, whose sha256 sum is :

$ sha256sum bitcoin-0.3.19.tar.gz.gpg
9e3d69700386772814b0e8c9723d8162c8d88c94479dbd24f18f280b

I turn this hash into a bitcoin address using the convertor in bitcoin block explorer

$ wget -O - -q http://blockexplorer.com/q/hashtoaddress/9e3d69700386772814b0e8c9723d8162c8d88c94479dbd24f18f280b
1BehjJ4trLTY1G148PntLkzb99UYYg5qWEotEAGudWXaW

Finally, I send 0.01 BTC to this address.

$ bitcoind sendtoaddress 1BehjJ4trLTY1G148PntLkzb99UYYg5qWEotEAGudWXaW 0.01

Hum...  bitcoin tells me it's an invalid address.  There must be a bug, but you get the idea, right ?

[Local]

You overslept. That is exactly what version 0.3.18 is doing using isStandard() function. It filters out all non-currency transactions unless I am not misunderstanding something.

You can't tell the difference, like grondilu showed.

[ShadowOfHarbringer]

You overslept. That is exactly what version 0.3.18 is doing using isStandard() function. It filters out all non-currency transactions unless I am not misunderstanding something.

You can't tell the difference, like grondilu showed.

We're not understanding each other.

I already pointed it out in when i was talking about Steganography. You cannot stop people from using bitcoin for other means than currency - because there is steganography, but you can limit it using currency fees and isStandard().

Anyway as i said, the less unnecessary data is in the chain, the better. More junk = greater bandwidth/storage requirements. And in case of bitcoin goes into micro-payments buisness, this will become a problem quickly.

[ShadowOfHarbringer]

It doesn't stop this:

You don't get it.  It's not steganography at all.  You don't really send any data to the network.  It is the same amount of "data" injected, whether you timestamp a "hello world" or a 1Go tarball !

It seems that I have to make an example to make it really clear.

So, I'm going to time stamp the tarball version of bitcoin, version 0.3.19.

First, I make a GPG signature of it :

$ gpg -s bitcoin-0.3.19.tar.gz

This creates a bitcoin-0.3.19.tar.gz.gpg file, whose sha256 sum is :

$ sha256sum bitcoin-0.3.19.tar.gz.gpg
9e3d69700386772814b0e8c9723d8162c8d88c94479dbd24f18f280b

I turn this hash into a bitcoin address using the convertor in bitcoin block explorer

$ wget -O - -q http://blockexplorer.com/q/hashtoaddress/9e3d69700386772814b0e8c9723d8162c8d88c94479dbd24f18f280b
1BehjJ4trLTY1G148PntLkzb99UYYg5qWEotEAGudWXaW

Finally, I send 0.01 BTC to this address.

$ bitcoind sendtoaddress 1BehjJ4trLTY1G148PntLkzb99UYYg5qWEotEAGudWXaW 0.01

Hum...  bitcoin tells me it's an invalid address.  There must be a bug, but you get the idea, right ?

Of course, and that is a kind of Steganography, which i already pointed out.
Steganography = hiding additional information in seemingly "standard" data, such as music, video, images, and now - bitcoin.

But such a transaction is a standard transaction, which is no problem at all because it does not bloat the blockchain with extra data.
The problem which i was talking about is people trying to push extra non-currency data into the block chain and mainstream client, making every transaction bigger, which would increase storage and bandwidth requirements.

[FreeMoney]

Okay, I'm pretty sure we agree. I don't think there needs to be extra room for data added either. But I do think normal transactions will be used to exploit special properties of bitcoin for non-monetary uses.

[bytemaster]

The problem with the 'block-chain' is that it is a serial process and there is NO way to get around that problem because to be 'deterministic' it must be a sequential process.

So as the demand to put things into the block chain exceeds the supply prices will rise.  The rise in price will be a market signal to increase the available bandwidth.

If I saw that the 'root' bitcoin chain was getting very expensive I would start a new 'currency' and an automated exchange with bitcoins.  The cost of using the new currency would be cheaper than the cost of using the 'reserve' currency (bitcoin). 

Eventually you would see 'clusters' of economic activity with synchronization points.

[Stephen Gornick]

[...]
Please brainstorm how to use bitcoins in new ways and post your ideas here.  

I've decoded the ASCII character that represents the amount sent in each of those 8 transactions:
0.66 BTC  = B
0.73 BTC  = I
0.84 BTC  = T
0.69 BTC  = E
0.32 BTC  = [space]
0.77 BTC  = M
0.69 BTC  = E
0.33 BTC  = !

That is steganography, no?  And that is using bitcoins in a new way?

This encoding of a message by creating spend transactions of certain amounts was performed by the Bitcoinica thief to communicate the message "expect mass leak soon":

 - http://bitcointalk.org/index.php?topic=81045.msg895878#msg895878