_ Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top up vote 3 down vote favorite According to the Bitcoin Developer Reference, the block header is 80 bytes total: As I understand it, the midstate (1st SHA block) contains 64 bytes of the block header (which fields in particular I do not know, but I do know it doesn't contain the nonce), and the 2nd SHA block contains the rest, only 80-64 = 16 bytes.Does this mean the 2nd SHA block is padded with 64 - 16 = 48 bytes?If so, why not make the nonce field, for example, 48 - 4 = 42 bytes larger (i.e., 52 bytes instead of 4 bytes)?That way, extranonce doesn't have to be in the generation transaction, thereby speeding up hashing, no?sha256 nonce block-header up vote 4 down vote It could have been done that way, at the cost of increasing the amount of space it takes to store and send block headers.It seems like block header storage was a big concern for Satoshi, (there's even a section in the whitepaper about it) but it's turned out to not matter very much.

Yes, (source) but your reasoning is flawed.Even if the nonce space were so large that it extended into another block, that would just mean that midstate would represent the state after hashing all but the last block (block in the cryptography sense, not the Bitcoin sense.)Also, if the block header were exactly 128 bytes, the padding would extend it to a third block.You only have 119 bytes before that happens.You can check 2^32 hashes before incrementing extranonce, after which you only need to do ten or so hashes before you get back to mining.Generally, in modern ASICs, even that part has been offloaded.There will be some sort of small processor within the ASIC, like an ARM core, which takes a block template as input and outputs block headers for the SHA256 cores to work on.So the cost isn't one of speed, but complexity.Like many things in Bitcoin, I think this is a technical decision that made sense at the time, but aged poorly.Browse other questions tagged sha256 nonce block-header or ask your own question.

The pull request submitted by Coinprism’s Flavien Charlon to increase the default maximum size of the OP_RETURN payload to 80 bytes has been merged into the master branch of Bitcoin last week.dogecoin securityThe colored coins protocol Open Assets was already able to handle 40 bytes without much problems, but an increase to 80 bytes will make it even more efficient.bitcoin hoffmanThe change to 80 bytes will also benefit other 2.0 protocols like Counterparty and Mastercoin.litecoin feb 2014What is the change about?Bitcoin transactions are made of inputs and outputs.The inputs indicate where the money is taken from, and the outputs indicate when it’s going to.OP_RETURN is a script operator which makes it possible to have a special output that doesn’t actually send money to anyone, but lets the creator of the transaction embed some data in it.

The amount of data that can be put in such output was previously limited to 40 bytes.Open Assets, being a light protocol, was able to fit everything it needs within 40 bytes.Other heavier protocols like Counterparty and Mastercoin can’t, so they instead use bare multisig outputs to store that data.Bare multisig outputs lets them store unlimited amounts of data in the transaction, however this comes at the price of occupying space in the UTXO set, which results in a higher memory footprint for all the full Bitcoin nodes on the network.OP_RETURN is more “ecological” as it doesn’t bloat the UTXO set, and so does not cost any memory to full nodes.With that change, those other protocols will be able to leverage OP_RETURN for some operations and be more mindful of the Blockchain.What does it mean for Open Assets Open Assets will continue to work as it already did, however the increase to 80 bytes allows for some interesting improvements.Firstly, the number of asset recipients in a single Open Assets transaction is limited by the number of bytes that can be stored in an OP_RETURN output.

Previously, a single transaction could send assets to up to 34 distinct recipients.After the change, it will be able to send assets to up to 74 recipients.This means that what had to be done though two different transaction can now be done with just one, reducing the amount of space used in the Blockchain.Because of the 40 bytes limit, that URL had to be quite short, forcing sometimes people to register a shorter domain name.With 80 bytes, most URLs will be able to fit without too much problems, making Proof of Authenticity validation easier.How does the future look?We really believe the change be beneficial for Bitcoin, by giving developers a clean way to store a small piece of data in transactions.It is worth noting that since Bitcoin 0.10, miners will be able to customize that value, either to lower it, or increase it.So far, there are less than 17,000 transactions utilizing OP_RETURN in the Blockchain.That means the space occupied by OP_RETURN data is at most 665KB (probably less) – compared to the entire Blockchain which will be soon 30GB.

Despite the controversial nature of the topic, we are happy that a compromise could be reached, and hope that this change will help foster innovation around Bitcoin while remaining “ecological” to the Blockchain._ Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top up vote 4 down vote favorite 2 I heard bitcoin-core 0.11 allows 80 byte OP_Returns, but I know miners operate different implementations and was wondering when it would be likely that 80 byte OP_Returns will be swiftly included in blocks.script op-return up vote 3 down vote As you can see, only 10.8% of nodes have upgraded to 0.11 and 29.3% of nodes use a pre-0.10 distribution.(Source: https://getaddr.bitnodes.io/dashboard/#user-agents) Considering that we don't know the hashing power of these nodes and don't know your definition of "swiftly included", there's no way to exactly answer your query.