i raised this issue ages ago. but core devs dont think its a problem
imagine it though.
someone is able to fill a block with just 1 transaction. secondly they could use the quadratic signature bug to make full nodes take longer to validate. thus cause network bottlenecks.
segwit HAS NOT fixed this because malicious users wanting to make a single tx still can.
core devs have refused to drop the sigops per tx, thus not reduce the risk. they foolishly say they trust the open freemarket model of trust that people simply wont do things to harm the network (bad security mindset)
some devs have foolishly thought to instead sooner or later, drop legacy validation, trying to force people into using segwit.(facepalm)
but as i said the cure is easy. reduce the sigops per tx,which stops people filling a block so easily
Topic: A block containing only 2 transactions - page 2. (Read 446 times)
The one positive thing that can be derived from this is that miners can mine transactions like this < 999,657 bytes > with zero fees, if they wanted to, but I doubt if they would want to do that for someone else. 
Nowadays that's highly unlikely with how much money there is to make by filling up the precious block space with organic transactions. If you want to test things as miner you can use the testnet do to so. It won't bother anybody in that case.The only more recent instance of a miner not utilizing the block space was Antpool, where they for some (probably toxic) reason mined a couple of empty blocks a day, and that without there being two blocks found nearly at the same time.
That might a block for miners which actually generate their reward base on the blocks mine and since that is their own work well done for then it can be mine with any fee or even less as every block just require a number of transaction to make up the size for scape through block.
It could have been someone just testing something, because it makes no sense mining a Block with 5569 inputs with zero fees under normal circumstances. I know some people spammed the network previously with loads of small transactions, but this does not look like any normal spam attack.
The one positive thing that can be derived from this is that miners can mine transactions like this < 999,657 bytes > with zero fees, if they wanted to, but I doubt if they would want to do that for someone else.
The one positive thing that can be derived from this is that miners can mine transactions like this < 999,657 bytes > with zero fees, if they wanted to, but I doubt if they would want to do that for someone else.
It is weird because he could have added more transactions and made more money in fees
Not in this case. The block was essentially full from this one transaction alone.isn't that precisely what makes it weird? this one transaction paid zero fees. even if the miner was mining his own transaction (and that's the only sort-of rational explanation), he could have collected 10x the fees by including transactions from the mempool. check out the next block, where fees totaled 0.59419256 BTC: https://www.blockchain.com/btc/block/000000000000000013ba348d19e2418fb49f79ea3fa7026c8c92483b4c61ba36
this miner was just being economically irrational and clearing out these brainwallets loaded with dust. they were doing the network a favor by clearing dust from the UTXO set.
edit: in fact yes, this was F2Pool, and i recall there was some discussion at the time about why they were doing this: https://www.reddit.com/r/Bitcoin/comments/3fggjj/someone_has_broadcast_a_transaction_with_20000/
It's not weird at all, when a pool/miner found 2 blocks with very short interval, it's done to make sure they receive the block mining reward.
not the case here. the prior block was found ~20 minutes earlier.
It makes perfect sense that a user would want to mine this transaction themselves for zero fees, rather than pay a fee and broadcast it for someone else to mine. It has 5569 inputs all of 0.00001 BTC for a total of 0.05569 BTC, and comes in at 999,657 bytes. Even at a fee of 1 sat/byte, the user in question would have lost 0.01 BTC or almost 20% of the transaction value in fees. Looking at the blocks before and after, the average transaction fee at the time was around 60 sat/byte, which would have cost this user 0.6 BTC in fees, or more than 10x more than the transaction was worth.
It is weird because he could have added more transactions and made more money in fees
Not in this case. The block was essentially full from this one transaction alone. 
Blocks with only 2 transactions aren't weird at all, but it's hard to see them nowadays.
The small blocks are not so rare actually. And indeed they happen when one block is mined right after another.
You can look at https://coin.dance/blocks to see the latest 1000 blocks and how many transactions they contain.
And I even found a "winner": block 592759, from yesterday, has only one transaction (the block reward).
I accidentally faced a weird block that contains only 2 transactions. I don't know if there are similar blocks.
Check block number 364292
https://www.blockchain.com/btc/block/000000000000000003dd2fdbb484d6d9c349d644d8bbb3cbfa5e67f639a465fe
There are only 2 transactions.
One of them is related to new generated coins and there is no issue with it.
But the other one:
The size is 999657 bytes and what makes me really surprised is the zero fee.
Check block number 364292
https://www.blockchain.com/btc/block/000000000000000003dd2fdbb484d6d9c349d644d8bbb3cbfa5e67f639a465fe
There are only 2 transactions.
One of them is related to new generated coins and there is no issue with it.
But the other one:
The size is 999657 bytes and what makes me really surprised is the zero fee.
As you can see that's an old transaction: 2015-07-07 18:19:07
Blocks with only 2 transactions aren't weird at all, but it's hard to see them nowadays.
In the past users was able to send transactions with zero fees and isn't hard at all if you know how to create a raw transaction with bitcoin core. But i think nowadays the same software gives a warning if the user doesn't add fees or if it's too low.
A miner can chose to include any transaction he wants in a block, even zero fee one.
It is weird because he could have added more transactions and made more money in fees
It is weird because he could have added more transactions and made more money in fees
I accidentally faced a weird block that contains only 2 transactions. I don't know if there are similar blocks.
Check block number 364292
https://www.blockchain.com/btc/block/000000000000000003dd2fdbb484d6d9c349d644d8bbb3cbfa5e67f639a465fe
There are only 2 transactions.
One of them is related to new generated coins and there is no issue with it.
But the other one:
The size is 999657 bytes and what makes me really surprised is the zero fee.
Check block number 364292
https://www.blockchain.com/btc/block/000000000000000003dd2fdbb484d6d9c349d644d8bbb3cbfa5e67f639a465fe
There are only 2 transactions.
One of them is related to new generated coins and there is no issue with it.
But the other one:
The size is 999657 bytes and what makes me really surprised is the zero fee.
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