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11

Messages are stored in a database at blockchain.info (so that text should probably be changed). For a while it did use the blockchain for storing messages but this was changed after concerns from a few of the core developers. Concerns were expressed by Matt Corallo here Oh god, thats awful...that is quite possibly the worst way to implement messages in ...


6

As described in the Alerts article on the Bitcoin wiki: Only alerts that are signed by a specific ECDSA public key are considered valid. A copy of the private key is held by at least Satoshi, Gavin, and theymos. All alerts that have not expired are relayed but the client displays only the highest priority alert that hasn't yet expired and wasn't ...


5

You will find that non-standard transactions are very hard to get into the block chain. Instead, encode the additional information as accounts and send a single satoshi to each account needed to convey your message. That way, you can use standard transactions. Transaction 28ccf29cfcc9f82d42793db770e7c7894d61ccf3d18299f34bda2e54415da287 is a particularly ...


5

Would it be possible to make using Bitcoin illegal by posting child porn or similar highly illegal content in the message of a transaction? Bitcoin, as a decentralised provision network of sorts, may have the same protections as given to ISPs and content providers. So unless the government is gunning for Bitcoin anyway - I'd say no, Bitcoin can not be ...


4

This is known as "tags", and it is 'blockchain.info' specific. You can use any web page, or bitcointalk.org user profile or bitcoin-otc Id as link. Your link page should contain your address. http://blockchain.info/tags


4

See the file chainparams.cpp in the constructor for class CMainParams: pchMessageStart[0] = 0xf9; pchMessageStart[1] = 0xbe; pchMessageStart[2] = 0xb4; pchMessageStart[3] = 0xd9;


4

You can, but you shouldn't. Bitcoin transactions should only contain the information needed for the world to verify your transaction. Anything else is essentially private information between the sender and the receiver, and would be useless bloat to the block chain (making it more expensive to maintain for everyone). That doesn't mean you can't have ...


4

There isn't a limit described by the BIP (https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki). In general, however, URIs might be encoded into QR codes, so their length should be kept as small as possible. GET requests often have limits on the length of the encoded URLs, something like 2000 characters (https://stackoverflow.com/questions/266322/...


4

Curently, with around 5000 nodes, a message shouldn't take longer than about 15 seconds to propagate. Typically, it's faster. Messages are forwarded if the Proof of Work is sufficient. There is no signature verification on forwarding, since only the recipient of the message can verify that. Nowadays, PyBitmessage runs the decryption attempts in a separate ...


3

You can not use the bitcoin address directly, but if the funds in the address have ever been spent, then you can see the public key associated with it in the blockchain, and you can encrypt with that using this python implementation: https://github.com/ikndevs/jeeq bitcointalk discussion here: https://bitcointalk.org/index.php?topic=196378.5


3

The cryptography Bitcoin uses for wallet private keys is ECDSA, using curve secp256k1: http://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm It is for signing messages, and does not useful for any method of encryption. There are other methods of encrypting and communicating a message, ... Gli.ph, BitMessage, GPG/OpenPGP, and more. If you ...


3

So is it one OP_RETURN parameter for each bitcoin transaction or per each input/output address? One OP_RETURN output per transaction regardless of the number of inputs and outputs is standard for 0.9.x bitcoin core clients. If its each transaction, so its safe to say its about .0001 btc to send 40 byte message? Yes, but you should not do it without ...


3

Block 138725 Transaction 930a2114cdaa86e1fac46d15c74e81c09eee1d4150ff9d48e76cb0697d8e1d72


3

You're right that public keys are generally unknown until coins are spent from their address, and that until coins are spent only a hash of the public key is published. While it's technically possible to use bitcoin public keys for the kind of encryption you're imagining, you're the first person I've seen talking about doing so. The satoshi client has an ...


3

Not in any way that is intended by the protocol. What do you mean by "ultimately the entity involved in a hypothetical trade"? It's just a hash of a public key, the corresponding private key to which you hold. What is preventing you from having a contact form or e-mail address in the online store?


3

As I see it, the key part is at the very end: "traceable in a decentralized ledger". That feature isn't described in the EFF page you cite, and I'm not aware that any of the services listed provide it. To see why this is important, imagine a scenario like the following: Major Smith receives a message at 0400 hours from Battalion HQ about impending enemy ...


3

Have a look to these data sources: https://bitcointalk.org/index.php?topic=1023190 https://github.com/petertodd/python-bitcoinlib/blob/master/examples/publish-text.py And of course the "modern" (and cheapest) way is storing arbitrary data in segwit part of transactions. I do not know is there ready tool for it, but it is not very difficult to write it. ...


2

Yes, you can now store up to 80 bytes via an additional, special output: https://bitcoinfoundation.org/blog/?p=290


2

The publicly shared Bitcoin address is a hash of the public key and nothing more. The only thing a Bitcoin address shares with public-key infrastructure (PKI) is that it is a type of cryptography and it is shared publicly. It does not provide the ability to encrypt a message so that only the owner of the private key can decrypt it. What can be done though,...


2

930a2114cdaa86e1fac46d15c74e81c09eee1d4150ff9d48e76cb0697d8e1d72 as reported by forum user makomk here.


2

This is a feature of blockchain.info only, because it is stored in their database. It is possible for anyone to associate a link ("tag") with any bitcoin address on blockchain.info, as long as it can be verified that the page the tag links to also contains the same bitcoin address. However, the example address provided in the question contains both a link ...


2

Bitcoin transactions - at least the part that ends up on the block chain - should only contain whatever is necessary for the world to validate them. Anything else is pushing extra costs (bandwidth, storage) to everyone who wants to run a full node, and isn't necessary. Of course, that doesn't mean that payments (as in: the full operation that takes places ...


2

I guess every time a getblocks message is needed because our client needs to check if the blockchain we have is the latest. Thats right. You can also compare the blockheight from the version message, but you will still need to check if you are not on a fork. So the getaddr messages follow the getblocks message I would say that up to you. If you ...


2

It isnt clear what exactly you're asking, but wiki is pretty clear on the structure of the response to a getaddr message. https://en.bitcoin.it/wiki/Protocol_specification#getaddr The response to receiving this message is to transmit one or more addr messages with one or more peers from a database of known active peers. So the payload of the response ...


2

As you can see in the protocol documentation the inv-object contains a field inventory (Inventory Vector). Inv-Object: Inventory Vector: You need to check the type field to know what the other node is sending. You will always receive a hash value, which is the identifier of a block or transaction.


2

Aside from OP_RETURN message attachment, what other methods are there to attach custom data? IP Transactions can do that. BIP0070 will probably be able to do that.


2

This might be a bit tricky because people generally tend to map binary data sequences to representations of real-life objects automatically, often conveniently slipping to lax and negligent assumptions. What is often left out is the importance of encoding, which is the essence that gives data a meaning. Without encoding, it's just a meaningless bitstream. ...


2

This message exists only on blockchain.info site. It is not a part of bitcoin protocol. You should not think, that it will exists forever, because blockchain.info is third-party-service Point your view to a OP_RETURN output scripts. http://bitzuma.com/posts/op-return-and-the-future-of-bitcoin/


2

We can find all instances in the code where the client will send a block message by searching for PushMessage("block". This is the only match: void static ProcessGetData(CNode* pfrom) { [...] pfrom->PushMessage("block", block); (Source.) This means that the standard client only ever sends a block message when specifically asked for it. That ...


2

Here's what I think how such a system could work: A relatively small but geographically distributed network of well-connected nodes maintain a ripple-like ledger (https://ripple.com/files/ripple_consensus_whitepaper.pdf) using a consensus algorithm. Each version of the ledger builds upon the previous version and contains transactions of different types. ...


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