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61  Bitcoin / Bitcoin Technical Support / Re: Unable to find the correct transaction hash on: November 20, 2018, 04:00:41 PM
This transaction is a segwit transaction (all coinbase transactions for blocks containing segwit transactions must also be segwit transactions). So you need to compute the txid as defined in BIP 144.
62  Bitcoin / Development & Technical Discussion / Re: Technical Perspective of bitcoins. on: November 20, 2018, 04:21:54 AM
I will like to know is anything that block chain and bitcoin is solving that earlier was unsolved and blockchain technology is first in solving it.
What Bitcoin solved with the blockchain was the problem of other payment providers and digital currency systems being centralized and prome to being shutdown. Using cryptography and hashcash as a Proof of Work system had been used before in Chaumian Ecash and B-money. However those relied on a centralized servers to order transactions and resolve double spends. Bitcoin's primary innovation from those systems was a method to resolve the double spend problem without relying on a central source of truth.
63  Bitcoin / Development & Technical Discussion / Re: Someone says about "running your own full node" but.. on: November 17, 2018, 08:32:24 PM
This thread got derailed, so it's being locked.
64  Alternate cryptocurrencies / Altcoin Discussion / Re: LOL. BitcoinCashABC has out-of-order transactions on: November 16, 2018, 06:39:27 PM
How do you verify such blocks?
You don't and just trust the miners that it is correct. That's the bcash model after all  Grin

But actually, to verify such blocks, you could do it in multiple passes. In each pass, you verify the transactions and skip the ones where the inputs are missing from the UTXO set. As you verify, the UTXO set is updated. Then you try to verify the skipped transactions again and so on. You would do this until there are no unverified transactions left, or until the UTXO set is not updated after a pass over the unverified transactions. At that point, all of those unverified transactions are invalid because their inputs are not in the UTXO set and the inputs are not from a transaction that is in the block.
65  Bitcoin / Bitcoin Technical Support / Re: Generating a Legacy Wallet on: November 16, 2018, 04:07:57 AM
The wallet.dat file is a Berkeley DB file. It is the standard database file that the Berkeley DB library creates. In 2010, the Bitcoin software used BDB 4.7. So you should tell the forensics company that they should look for BDB 4.7 database files.
66  Bitcoin / Development & Technical Discussion / Re: Development Environment to get started on: November 16, 2018, 04:02:26 AM
This is a big fat lie or misbelieve.

Bitcoin is carefully modified to only work in:

Latest GNU C++ compiler.
This is completely untrue.

Bitcoin Core does not use the latest C++ nor the latest boost versions nor even the latest gcc. Bitcoin Core currently uses C++11, but the latest is C++17. The current boost version used is 1.64 which was released more than a year ago. But using newer versions of boost should still work.

It can also be used with different compilers such as clang and Visual C++. There are even instructions, project files, and a CI system for using MSVC and Visual Studio! Furthermore, building with clang is supported too.
67  Bitcoin / Project Development / Re: Block Explorer Development on: November 14, 2018, 04:14:59 AM
Thanks for you reply, but everything you said is already explained on my question.
Not really. You had a question about insight. I answered your question about insight and how you can run it locally without a third party service.

Answering your last paragraph, yes, there's ABE.
ABE is not maintained. It is missing things like segwit support which makes it difficult to use with modern node software.
68  Bitcoin / Project Development / Re: Block Explorer Development on: November 13, 2018, 05:03:30 PM
You won't be able to run a block explorer if your node is pruned. Pruning throws away information that isn't necessary for the node to function (old blocks and transactions that have already been verified). However the point of a block explorer is to be able to see those data and explore them, so pruning is inherently incompatible. You will need to run a proper archival node (one which stores the entire blockchain) in order to operate any sort of block explorer.

The Insight explorer uses the insight API which uses it's own backend node software called Bitcore. You can run that software, then install the insight API service, then the insight explorer.

Otherwise you will need to write your own block explorer as I don't think there are any other maintained (and I'm not entirely sure insight is maintained) open source block explorer software.
69  Bitcoin / Bitcoin Technical Support / Re: How to go from testnet to livenet on: November 10, 2018, 03:27:45 AM
Your questions is pretty vague. What part of "going from testnet to livenet" do you need help with? Connecting to nodes? Conecting to bitcoind? Addresses? etc.
70  Alternate cryptocurrencies / Altcoin Discussion / Re: How to revert made fake coin exploit code's bug? on: November 03, 2018, 12:50:53 PM
So litecoin forked coin is safe?
No. Litecoin, and every other coin that was forked from Bitcoin or pulled in new code from Bitcoin are vulnerable, unless they have also pulled in the fix.

And if this happened, what solution can be used to fix?
Pull in the changes from Bitcoin Core. Sync a new node with that software. Once it reaches the invalid block, it will reject it. From there, start mining a fork. Once that has more work than the original blockchain with the invalid block, that will become that coin's blockchain.
71  Bitcoin / Development & Technical Discussion / Re: Does Bitcoin Core in prune mode support mining? on: November 02, 2018, 02:36:58 PM
I have currently set my Core node to -prune=550, but I see that getblocktemplate returns data, so can one mine on the pruned node?
Yes, you can mine.

With only 550 blocks stored, how can/would a pruned node make sure that an input given by user to be signed in a block isn't a double spend? There'd be no way to check that on such a node, right?
(E: Although i think there's probably a mechanism for this, otherwise it wouldn't be able to verify any transactions at all.)
That's not how Bitcoin Core works. Pruned nodes are still full nodes. They have validated every block in the blockchain; they still validate and relay every single valid block and transaction they receive. They are, by definition, full nodes. The difference between pruning and not pruning is whether the node can serve historical blocks to new nodes coming online. Everything else is the same; they can be miners, they will still receive all blocks and transactions, etc. The UTXO data that is necessary for validation is not pulled from the block history, that would be rather slow. Instead, when a block is validated, the UTXOs are copied to a UTXO database and the UTXOs that were spent are removed from that database. Pruning still keeps that database and all of the UTXOs, so validation is still works.
72  Bitcoin / Development & Technical Discussion / Re: scriptPubKey not verified upon locking, but when trying to unlock it on: November 01, 2018, 03:12:49 PM
That is hardly an explanation, we are talking about syntactic correctness here, not semantic.

A scriptPubKey can be preliminarily validated against this kind of mistakes that I described above, I was not expecting it to be run on its own because I know they only make sense concatenated together. However, errors like these can be caught up without actually running the script...
It is up to the transaction creator to ensure that their script is constructed correctly. There are tools available that let you do this. It is not the Bitcoin network's job to be your debugger. Further, any script is syntactically correct, even if it is "wrong". There really is no syntax.
73  Bitcoin / Development & Technical Discussion / Re: scriptPubKey not verified upon locking, but when trying to unlock it on: November 01, 2018, 01:43:51 PM
1) why it worked in the first place, doesn't the scriptPubKey go via the same validation rules as the scriptSig ?
Because the scriptPubKey is only half of a script. It cannot be executed. If it were, it would always fail because a scriptPubKey is just part of a script. Same with the scriptSig; it is just part of a script. On their own, neither can be executed and get a successful result.

2) why would bitcoind even care about the scriptPubKey of the UTXO i'm trying to spend, i thought it was supposed to just first run <scriptSig> then keep the stack and run <scriptPubKey> (which it may already consider valid...?)
The scriptPubKey defines the spending conditions, i.e. what needs to go into the scriptSig. It has to run the scriptPubKey to ensure that the scriptSig is correct.

You can think of the scriptSig being the first half of a script and the scriptPubKey being the second half. On their own, they mean nothing and when executed on their own, they will fail. But concatenate them together, and you get a full script which can be executed. That is conceptually what script validation does. Before script validation, neither the scriptPubKey nor the scriptSig are considered valid.

The scriptPubKey in an output can be anything, it is not and cannot be validated when it is created. There have been multiple instances of people putting random garbage in scriptPubKeys. Those transactions are totally valid and in the blockchain. It is just that the outputs are not spendable because attempting to spend them would result in an invalid script.
74  Bitcoin / Bitcoin Technical Support / Re: raspberry pi errors on: October 31, 2018, 08:36:42 PM
Your databases are corrupt. Start bitcoind with -reindex.
75  Bitcoin / Development & Technical Discussion / Re: Flaws in LN (Lightning Network). on: October 31, 2018, 08:35:19 PM
This thread is devolving into flaming each other. Thus it will be locked.
76  Bitcoin / Development & Technical Discussion / Re: When bitcoind starts up, In where and which function difficulty is calculated? on: October 30, 2018, 01:53:12 PM
That error is completely unrelated to the difficulty. The getblocktemplate RPC will refuse to return a valid block template if it thinks it is not fully synced. That will happen if the timestamp of the most recent block is not within two hours of the computer's time.

Thank you so much for the reply. I'm a bit confused a little bit here. The most recent block is my genesis block. If I create a new genesis block and do the compiling and starting up process, same thing will happen. That's why I speculated about difficulty.You say there is no problem with the network and I can create transactions properly?
There are other conditions that can trigger this error, it is not just the timestamp. It may be possible that the fact that there is only the genesis block is what is causing the problem. I think it could be that just having the genesis block even if it is up to date will still cause the node to think it is still in InitialBlockDownload. You can just make the error go away by commenting out or removing these 2 lines in src/rpc/mining.cpp.
77  Bitcoin / Bitcoin Technical Support / Re: "Premature end of block data" when using linearize on: October 30, 2018, 12:42:46 AM
./ linearize.cfg
Runs fine and reads all the blocks but seems to try to read the next blk file that does not exist.
I do get a bootstrap.dat file but I also get a "Premature end of block data". I can't tell if this is a normal ending to running the script or not.
That does not seem like the normal end of the script. That error means that it was unable to open the next file of block data which it was expecting. This could be due to a configuration error, or that perhaps the node is not synced to where you believe it to be. However, the resulting bootstrap.dat file should still be valid and usable. It just does not contain as many blocks as you expect it to contain.

How does one confirm that a bootsrtrap.dat is, in fact, accurate or properly done?
By trying to load it into a version of Bitcoin Core that can read the bootstrap.dat file and seeing if it does load it.
78  Bitcoin / Development & Technical Discussion / Re: Please, help with bitcoin core on: October 30, 2018, 12:39:04 AM
Those errors look like permission errors. Make sure that the user that bitcoind is running as has permission to read and execute the file. Note that the user that you are currently using in the shell is not necessarily the same user. Further, if you have to use sudo to do anything to the file, then something is probably wrong, unless bitcoind is being run as root (which you shouldn't be doing).
79  Bitcoin / Development & Technical Discussion / Re: When bitcoind starts up, In where and which function difficulty is calculated? on: October 30, 2018, 12:31:52 AM
So you mean that if I change nBits and consensus.powLimit parameters in chainparams.cpp the whole network should work fine ? but I face a problem when I run two bitcoindd :

The two servers start up properly but when i type the command "bicoin-cli getblocktemplate" I get

error code: -10
error message:
Bitcoin is downloading blocks...
That error is completely unrelated to the difficulty. The getblocktemplate RPC will refuse to return a valid block template if it thinks it is not fully synced. That will happen if the timestamp of the most recent block is not within two hours of the computer's time.
80  Bitcoin / Development & Technical Discussion / Re: How are bitcoin blocks verified? on: October 29, 2018, 04:01:13 AM
By definition, everything in a computer is a string of bytes, even text  Grin

All kidding aside, a block has a serialized byte format. It is not transmitted over the network in JSON. The JSON output that you get from Bitcoin Core is merely something that is human readable. That is not actually how blocks are transmitted over the network.

The block format is just bytes with bytes at certain positions having specific meanings, as defined by the format. You can see the hexadecimal representation of these bytes if you call getblock with verbosity level 0 (i.e. getblock <hash> 0).

A block is not a script. Scripts are part of transactions and are in a specific field for scripts only.
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