Questions tagged [blockchain]

The Ethereum blockchain is a distributed database based on the Ethereum whitepaper specification and stores both the full transaction list and the most recent state.

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2answers
2k views

What does it mean to “seal a block”?

In both the Ethereum chain specification format and in Parity's documents on private chains, you see the term seal a block. What exactly does that term mean? How is it different than mining a block?...
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1answer
10k views

How can I specify an external harddrive as the download target for the Mist blockchain in Ubuntu?

How can I specify an external harddrive as the download target for the Mist blockchain? Hi there, I am using Linux Ubuntu 15.10 My harddrive is quite full and I need to download the whole Mist ...
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1answer
7k views

Could somebody please explain in detail what this Ethereum contract is doing?

I am new to ethereum & blockchain technology and trying to understand somethings(Etheruem, Truffle, DApps etc.) here and there from the internet. From Ethereum official website, Create a ...
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1answer
4k views

Mining stops after generating DAG for epoch

I first initiate the node using the genesis file with the command: >geth init genesis.json Then i start the blockchain network using the following command: >geth --identity "node1" --rpc --...
8
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1answer
2k views

Can a mined block have an odd number of transactions? If so, how does the Merkle root in that case?

Merkle Tree pairs transactions and hashes them and the process continues till we get to the root. But how would this pairing process work if the number of transactions were odd?
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Is it possible to check that does client's node's block number matches with the blockchain's best(latest) block number?

I have a sorted linked list that contains around 1000 items. When I receive a new item my goal is to push the item to the list keeping the sorted order. So if I receive very small value, I am required ...
6
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1answer
998 views

Will I be able to mine having my whole blockchain imported using the --fast flag? (Geth)

Having the same problem as in this question: Corruption on data-block while synchronising I restarted my synchro on the fresh/empty data directory using the --fast flag. According to this answer: What ...
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2answers
3k views

How to fix “address already in use” error when attempting to launch geth console?

I'm downloading the chain and I've processed more than 2 million blocks so far. I'm trying to attach to the geth console to view the syncing status, but I've tried typing geth console in another ...
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1answer
705 views

Invalid sender when sending Raw Transaction, signed w/ ethereum-tx on PHP

I am using PHP and ethereum-tx library https://github.com/web3p/ethereum-tx to sign transactions but when trying to send them to the node I got an "invalid sender" error. Besides, exactly the same ...
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1answer
565 views

How to send ERC20 Token?

I try to send Token based on Erc20. and I can send Ether and something function but i dont know how to use transfer function in javascript like that. function transfer(address _to, uint256 _value) ...
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3answers
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How can i tell if geth is done running?

Well i am new trying to mine and i did the "C:>geth --rpc" and its still going how will i know when its done? i did all the steps leading to this but my pc just keeps running the INFO [05-18|23:32:...
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1answer
735 views

Block header structure change under Proof of Stake?

The yellow paper describes the below block header structure: This includes difficulty, beneficiary, mixHash and nonce values. Presumably these will be redundant under Proof-of-Stake. How will the ...
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2answers
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Retrieve CHAIN_ID of the executing chain from a Solidity contract

Is there a way to directly be able to retrieve CHAIN_ID information about the executing chain from a smart contract? I know that for any chain that has EIP-155 implemented, CHAIN_IDs are retrievable ...
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2answers
504 views

Checking the blockchain within Solidity contract

I want my contract to check a given range of blocks and see whether there are any transactions between a given pair of addresses. Is this possible to do in Solidity? Otherwise how would I do it?
4
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1answer
936 views

Getting current full state

In my quest to understand ethereum in depth, I ended up in this article, which contains the following image: If the image above is correct, only the changes in state are taken in account to create ...
4
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1answer
359 views

Why does geth -light start importing block headers from 3297471

I've been using geth to download the blockchain (on full) and one of the requirements for my research involves the use of light clients. I used 2 computers to download the blockchain on the -light ...
4
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1answer
8k views

Optimal sync mode for running an ethereum node that can process transactions

I need to run a local ethereum node, I've downloaded mist wallet but I've had some issues. I have to redownload the whole blockchain again, and I noticed that the problems I had could be related to ...
3
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2answers
738 views

Syncing keeps behind the blockchain

I am trying to run a geth node just to learn what I can do with it. I started geth with fast syncing. The problem is that it never syncs and always lags behind ~100 blocks. My datadir is on my HDD and ...
3
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1answer
201 views

Smart Contract different behaviour on testnet vs Solidity Browser

The following smart contract behaves differently on Solidity Browser and testnet: pragma solidity 0.4.2; contract mortal { address owner; function mortal() { owner = msg.sender; } ...
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2answers
640 views

Geth 1.6.1 hangs throwing “unexpected fault address” fatal error

Since upgraded to version 1.6.1, Geth node hangs form time to time (once a week) with following fatal error: fatal error: fault [signal SIGSEGV: segmentation violation code=0x1 addr=0x7f6453b72c88 pc=...
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3answers
695 views

Why don't Ethereum increase the block gas limit?

Why don't Ethereum increase the block gas limit? In my understand, it can increase total throughput(transactions per second), but also increase uncle block rates either. But i couldn't find any exact ...
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0answers
144 views

Read function returning blank array in geth

I have deployed a smart contract on geth which has 2 simple read, write functions in it. Then I called the write function; e.g. payment.place_order("Laptop", 10,{from:eth.accounts[0]}). After the ...
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1answer
834 views

Is Quorum production ready

Quorum is private permissioned blockchain network.Is it production ready or still in beta/Proof of Concept stage?
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1answer
749 views

I'll never reach final block updating with geth, it's too slow

I´m updating my ethereum blockchain with geth. But I feel it is going really slowly. Each block is done in 1 minute, sometimes 30 seconds, but at this pace I'll never reach the final block, ...
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2answers
206 views

Parsing contract method output as an array of fields

I have a constant method in a Smart Contract that returns this array: (uint256 _field1, uint256 _field2, uint256 _field3, address _field4, string _field5) When invoking it I got this hex result: ...
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1answer
237 views

What is the difference between create and newAccount in web3js?

There are two ways to create account one is web3.eth.accounts.create() and web3.eth.personal.newAccount(); function, When I use newAccount() function account is created in my local geth client but ...
6
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1answer
761 views

peers keep connects and disconnects into private Ethereum blockchain

I have two servers that are connected into local private ethereum blockchain successfully and they do mining as well. After few minutes one of them disconnects and after that it re-connects again and ...
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1answer
416 views

What is the proof that Mainnet can't be reset?

It has been argued that the Morden testnet can be reset any time. How can one verify that this is not possible with the mainnet?
5
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1answer
465 views

Error in download full data with Geth ( transaction field in Block is empty)

I'm trying to download full data of ethereum block chain. But when I check the result, I found an error. From block 1 to 46146, field tx is empty,it means that there is no data for transaction. Does ...
5
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1answer
14k views

Is there a way to track block synchronization progress in geth? [duplicate]

I just started up geth after importing my presale wallet. I'm getting a lot of block import messages like this: I0305 17:40:03.815435 10833 blockchain.go:1251] imported 256 block(s) (0 queued 0 ...
5
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1answer
575 views

Can a contract read the address of past miners?

I am trying (in solidity) to write a contract that needs some statistics on the past few miners. E.g., who mined the last 100 blocks. I know that for the current block I get the address as explained ...
4
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1answer
314 views

How can empty accounts with a nonce of zero appear on the blockchain?

Recently I have heard about zero balance accounts with a nonce of zero appearing on the blockchain. My understanding is that any account that has been used in a transaction must have a nonce greater ...
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3answers
1k views

Storing data pointer on blockchain

How can I store user data on smart contract without exposing it to other nodes to read ? I read somewhere that you can store data pointers instead of data on contract and use it for offline data ...
3
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1answer
273 views

Blockchain syncs in Mist, but not in Geth?

I'm trying to mine. When I try syncing in Geth, all my handshakes fail and I cannot add peers. My port 30303 is open and syncing still doesn't occur with the --nat=none flag. Mist syncs no problem. I'...
3
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1answer
205 views

what is the use of difficulty in ethereum blockchain?

Why ethereum has introduce difficulty and what is the use of difficulty in blockchain? I have seen that we can use static difficulty for blockchain . So why we not use static difficulty for public ...
3
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0answers
191 views

Solidity benchmarking metrics [duplicate]

I am trying to figure out the best ways of benchmarking Solidity contracts. As with normal benchmarking, I presume one would basically want to measure computational effort and storage overhead: gas ...
2
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1answer
4k views

Block time and confirmation time

I have been reading in different papers and comments these two concepts and I would like to know the difference between them(if there is, sometimes it is a bit confusing). I understand that the block ...
2
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2answers
10k views

Getting transaction history for a particular account

I want to get the list of all the transactions which have been performed by/on an account in my private blockchain. I tried using the function getTransactionsByAccount(accountAddress, ...
2
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1answer
252 views

Connecting to blockchain on azure using web3.js and websocket

right now, I am trying to write a service using web3 which will 'subscribe' to all 'perndingtransactions' on blockchain to perform further actions. web3 documentation says that 'Httpprovider' cant be ...
2
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1answer
118 views

Ethereum - Does it only have a single blockchain?

I still do not get if ethereum creators want it to be single blockchain or not? If not, where are instructions for creating my own blockchain to play with?
2
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1answer
964 views

Ethereum chain size

Currently I don't have an up to date version of the real/test net on my PC. I've tried to find a blockchain explorer that will show the size of the chain in GB. Specifically for Geth, or atleast for ...
2
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1answer
118 views

Difference between ERC 20 and ERC 721 transaction receipt

I want to fetch certain transaction logs from a local ethereum node. For that, I need to identify how to differentiate between ERC 20 and ERC 721 transaction receipts. From what I saw on Etherscan, i ...
2
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2answers
934 views

Where can the parity blockchain files be found?

On my Mac I am looking for the Parity blockchain file for the ropsten chain. I checked the following locations: ~/.parity and ~/.local but both directories don't exist. ~/.ethash contains 1gb sized ...
2
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1answer
131 views

When 2 blocks or more are distributed at the same time, but the longest one delayed

I have a problem understanding the concept of handling two or more blocks that distributed at the same time (in the blockchain network). As far as I understood, When I get 2 or more blocks at the ...
2
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1answer
102 views

Are the timestamps of blocks for Ethereum only accepted when they are monotonically increasing?

Are the timestamps of blocks for Ethereum only accepted when they are monotonically increasing? If yes, why? And why other blockchains like Bitcoin and other blockchains with shorter block time can ...
2
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1answer
765 views

How is the block gas limit dynamically adjusted?

What mechanism lies behind adjusting the block gas limit dynamically? Is it the miner that mined the most recent block who decides whether to adjust the gas limit or not? How much can the block gas ...
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1answer
31 views

State only node

Is it possible for the network clients to just keep the latest network state (without keeping track of the past transactions) while not harming the network security? That is, is it really needed to ...
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1answer
64 views

How the hashing of the block data ensures the data integrity?

In ethereum, as a node controller I can able to access the leveldb. If I try to modify some value directly into the db, the value of the new hash and the next block's parent hash doesn't match right ?...
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1answer
350 views

How Ethereum consensus validates same transaction from different miners? [duplicate]

In an Ethereum node, my brief understanding regarding transaction flow is below. When a client initiates a transaction, all mining nodes receives this request. Based on gas price, miner choose to ...
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0answers
83 views

Why is my node taking so long to sync? [duplicate]

I downloaded the ethereum wallet, and its taken a few days yet its still syncing. Im on block ~701,000 thus far. Is something wrong? Is it supposed to take this long?