How can I calculate/estimate how quickly a machine can verify transactions on the blockchain?

If I have some machine with particular specs in mind (processor/memory/bandwidth), how can I estimate how quickly that node can download and verify transactions? In a quick search I wasn’t able to find any numbers for verification speeds run on different machines, so that would be helpful too.

I have seen this question, but my question is more focused.

Update:

I found one bit of data about this: a lower bound of verification of last year’s blockchain in about 20 days (projected, not tested). This amounts to about 170 transactions per second of verification.

No transactions are showing on my Blockchain page

I’m new to this but I know how to use the request button on BlockChain to receive money? The Bitcoin was sent to the address I provided and I didn’t get it. I’ve received money before and sent money and none of this is showing. Transactions aren’t even showing on my blockchain home page. I’ve always used the same email address. There is always change in my Blockchain account and that not there is either. I done this over may 7times probably and never had an issue. Was I hacked? The day I requested the money I thought it was odd that no change was in there because there is always 95 cent to 50 cents in the blockchain. Because the money was sent 10 days ago. The company sent me all the information and I’ve never had any issue before with blockchain. Can somebody help? NO TRANSACTIONS are showing up in my whole time using blockchain and I find that odd.

How to store private data in blockchain and smart contract

Following my previous question on this topic Is there a way to store and share a private key through blockchain?, I might have a solution but I would like to improve the process.

Image that A is the owner of some private data, and want to give the ownership of this data to B, another member of the blockchain. The data is a private key so it can not be public, but it can be encoded using A or B public key.

So:

  • Secret data is encoded with A public key, and stored in A informations data /
  • B want to by A secret data
  • A decode the secret data (using his private wallet key) and encode the secret data with B public key
  • Ownership of the data is given to B
  • Now only B (and A also but that’s a different story) can decode secret data.

Is there a way to simplify this process using smart contract? I assume a smart contract have access to A and B public key, but can a data be encoded/decoded with private key of the one executing the smart contract?

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Bcoin initial blockchain sync progress isn’t saved

I’m using bcoin and it’s class FullNode to run a full Bitcoin Node. Here’s the configuration:

const node = new bcoin.FullNode({         prefix: '/mnt/d/bcoin',         network: 'testnet',         indexTX: true,         indexAddress: true }); 

And then I start the node with this code, identical to the one they use in their official example.

(async () => {         await node.open()         await node.connect();          node.on('connect', (entry, block) => {                 console.log('%s (%d) added to chain.', entry.rhash(), entry.height);         });          node.on('tx', (tx) => {                  console.log('%s added to mempool.', tx.txid());          });          node.startSync(); })().catch((err) => {         console.error(err.stack);         process.exit(1); }); 

It seems to be working fine, I get notifications of the blocks added in the console. the program crashes once in a while to the lack of memory, however, I found a fix to that. The progress of sync seems to never be saved, however. If I were to restart the app when it’s on 1,000,000 blocks in (testnet) – the sync will start over. The files are created in the /mnt/d/bcoin folder and it’s already 10 GB in size. In comparison to the official bitcoin node – it always carries on the sync that’s already in progress. I have never been able to finish the inital blockchain download with bcoin because I run it in my PC and it always fails for various reasons. So is it expected behavior for bcoin to reset its IBD progress every time? Would it read the existing block files after IBD?

After downloading the entire Bitcoiin blockchain from a torrent, what are my next steps to link it to Bitcoin Core 0.17.1?

I downloaded the entire bitcoiin blockchain into my external mounted drive as seen below and named the directory bcore.

I then did a symlink to that folder like this in my home folder (~) location :

ln -s /mnt/xxxx/bcore .bitcoin

I then ran .bitcoind, but I thought I downloaded the entire blockchain. How do I know if its just syncing with what I already downloaded or is it literally downloading everything again? Is there a way to just skip verifying blocks if that is what it is doing. I don’t have the time to wait hours for this since I already waited 23 hours to download the blockchain already.

Is there a file I can just download where it skips the block verification?

Also another reason why I think its downloading it again is because when i run bitcoin-qt on the bottom it says: “Syncing with Network” Which leaves me a bit confused.

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What happens in a small scale blockchain network?

My main question here is, is this understanding correct or have I misunderstood something? If this question would be better for Reddit then I apologise in advance and I’ll move to there. Thanks.

Scenario:

So technically I could download the bitcoin source code and run my own altcoin (let’s call it pokercoin) on a network of 5 computers (for me and my 4 geeky friends who wanted to play poker without chips).

If I’m understanding correctly, we would each be running pokercoin source code/qt on our laptops and no other computers would be needed to keep the thing running (or maybe we would need to run something else to ensure the network works, because otherwise there is no other way of the network doing all the IP level stuff? Or do nodes do this and run something other than the bitcoin source code?).

When I make a payment, each of the other 4 computers receives a copy of that transaction, and they all add this to a block of 1 transaction which gets appended to our very short blockchain after 10 minutes (because hypothetically my computer is able to solve in 10 mins).

If 2 of us made a transaction, (the new block to be added has 2 transactions), but the other 3 computers wrote their own block which diverged in truth to my computer and my friend’s computer, then this 51 percent attack would beat the previous block to be appended (or is it added only after ANOTHER block is added (because this is now the longest chain).

We all also get new pokercoin for being miners in our own system (or maybe it is only those running different code who get to be miners).

Finally, none of us actually argues over having any money, because we know that ‘how much we own’ is actually only made up of the network iterating over every transaction that happened in order to calculate our amounts (and this happens every time a new block is made).

We also don’t argue over block sizes, because there are 5 of us.

Create a raw transaction and broadcast it to blockchain using bitcoin core

I have a address- n3xYQtxvVwpBPSbgGsGRdMWz1YTUjakiMV, amount that i want to send-1 BTC and i have a private key. How can i create a raw transaction using it and broadcast it to blockchain using bitcoin core.

I have tried this command:

bitcoin-cli createrawtransaction '[{"txid":"dbdc2e2c7f143af70c5e7e8725f55d226b3c058d7bf34a303‌​091b3c6a514848c","vo‌​ut":1}]' '{"n3xYQtxvVwpBPSbgGsGRdMWz1YTUjakiMV":1}'  

and this: bitcoin-cli sendrawtransaction XXX

What is the need of consensus by proof of work when digital signature is already being used in blockchain

I am learning about how Bitcoin works under the hood. I am unable to understand why consensus is needed if digital signature is already being used. By my understanding, consensus is used by nodes to achieve same state of the blockchain, where same state means the chain with no tampering(theoretically). But doesn’t digital signature achieve the same thing? What is the need of achieving same state if the transactions which are not authentic are already being declared invalid.