An odd looking tx.

[CuriousCarl]

What happened to the tx input in this transaction? The output says "nulldata". What does that mean?

Code:

C:\Program Files\Bitcoin\daemon>bitcoin-cli.exe getrawtransaction db3cc99eb91533
bf0973b62c572589925df8e1f1501678d54034261b5a4ccfbf 1
{
    "hex" : "010000000151693cb178b2d7396532865aaa35d054be0db6aaf2ca3b5adbf90bcf7
28eaabb3a0000008a47304402202b0c035d0075adae560688dae0fcf78142e96bcaf9fafd510940c
76c5629936d0220037e006368f3fc09af40f862df4bcc10cf0f239a40364cffcd1fabb0904f5f830
14104bd184b34e4e20698a7670854e16f68c4ca2f9326572342998bdf1b1c4685644c2374e40c19c
a20eeb3439e3255d468d3e92aa32f577df99bdb409c8f064462f7ffffffff0100000000000000002
a6a28444f4350524f4f46f303df84d32e8c5c3433a807d4b6da36f782bc4e03c6cf41a907ea2193a
0e16b00000000",
    "txid" : "db3cc99eb91533bf0973b62c572589925df8e1f1501678d54034261b5a4ccfbf",

    "version" : 1,
    "locktime" : 0,
    "vin" : [
        {
            "txid" : "bbaa8e72cf0bf9db5a3bcaf2aab60dbe54d035aa5a86326539d7b278b1
3c6951",
            "vout" : 58,
            "scriptSig" : {
                "asm" : "304402202b0c035d0075adae560688dae0fcf78142e96bcaf9fafd5
10940c76c5629936d0220037e006368f3fc09af40f862df4bcc10cf0f239a40364cffcd1fabb0904
f5f8301 04bd184b34e4e20698a7670854e16f68c4ca2f9326572342998bdf1b1c4685644c2374e4
0c19ca20eeb3439e3255d468d3e92aa32f577df99bdb409c8f064462f7",
                "hex" : "47304402202b0c035d0075adae560688dae0fcf78142e96bcaf9faf
d510940c76c5629936d0220037e006368f3fc09af40f862df4bcc10cf0f239a40364cffcd1fabb09
04f5f83014104bd184b34e4e20698a7670854e16f68c4ca2f9326572342998bdf1b1c4685644c237
4e40c19ca20eeb3439e3255d468d3e92aa32f577df99bdb409c8f064462f7"
            },
            "sequence" : 4294967295
        }
    ],
    "vout" : [
        {
            "value" : 0.00000000,
            "n" : 0,
            "scriptPubKey" : {
                "asm" : "OP_RETURN 444f4350524f4f46f303df84d32e8c5c3433a807d4b6d
a36f782bc4e03c6cf41a907ea2193a0e16b",
                "hex" : "6a28444f4350524f4f46f303df84d32e8c5c3433a807d4b6da36f78
2bc4e03c6cf41a907ea2193a0e16b",
                "type" : "nulldata"
            }
        }
    ],
    "blockhash" : "0000000000000000000119f88871f8a3c3b7be053c98b31e9c4676df30243
cfe",
    "confirmations" : 7913,
    "time" : 1418331464,
    "blocktime" : 1418331464
}

Blockchain.info also has trouble showing this transaction. I.e. it doesn't have an output address?
https://blockchain.info/tx/db3cc99eb91533bf0973b62c572589925df8e1f1501678d54034261b5a4ccfbf?show_adv=true

There is btc input, but there doesn't seem to be any output address. How does that work?

[andytoshi]

Hi CuriousCarl,

Bitcoin transactions are actually chained together in a more general way than simply "address to address". You might find this overview informative. While ordinary spend-to-address transactions are created such that only the owner of an address[1] can redeem the coins. However, it's possible to create transactions whose outputs can be redeemed given other conditions: some trivial ones are "anybody can spend" and "nobody can spend". What you're seeing here is an example of the latter. Such transactions are used because it is possible to embed other, unrelated data, into such transactions. This is antisocial behaviour because it consumes Bitcoin users' bandwidth and storage (which presumably they are donating for the sake of Bitcoin, not whatever unrelated thing is being stored), but it's technically possible so people do it.

Addresses aren't directly part of the Bitcoin protocol; they're just one way of using Bitcoin's scriptable signature system to manage asset transfers. blockchain.info uses a broken model of what transactions and addresses are, and therefore gets confused quite easily. Generally if you encounter a weird transaction, checking what bc.i thinks of it is exactly the wrong thing to do.

[1] By this I mean somebody in possession of a corresponding private key; this often doesn't really correspond to "ownership" on the user level, for example if your coins are stored at an exchange. Then the exchange might own the address even though you own the coins. It is generally true that addresses are a pretty low-level thing and don't correspond well to user expectations, so in a more user-friendly system users would not ever see addresses at all. There is progress in this direction but it's slow.


Andrew

[CuriousCarl]

Thanks for the explanation. Very clear.

It's going to be interesting to see how many of these "not to address" txs there are in the blockchain. I knew about multisig addresses before but not this anyone can spend and nobody can spend, and there seems to be a few more when looking at the core cpp code.

[Tjopper]

It looks like some kind of "proof of existence" I think we display it more properly:

https://www.blocktrail.com//tx/db3cc99eb91533bf0973b62c572589925df8e1f1501678d54034261b5a4ccfbf

Best Regards,
Jop

[Cryddit]

I read it as someone publishing some version of a hash on a document.  It's getting buried in the blockchain as a proof that he had it at a particular time.

Presumably, at some later time, he asserted (or will assert) that he had the document at that time and offer the blockchain tx as proof.

Which as andytoshi pointed out, probably has nothing to do with Bitcoin itself.  For all we know the author of this tx is just establishing his copyright on something, or proving that it hasn't been tampered with since that date.

[unamis76]

Are these "nulldata" transfer those composed of "blockchain vandalism" or "blockchain graffiti"?

[samson]

Are these "nulldata" transfer those composed of "blockchain vandalism" or "blockchain graffiti"?

That's what some people say, however there are other ways of storing data in the blockchain which use up much more space.

Imagine 100's of tiny outputs encoding some data in a single transaction...