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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How can I force a redownload of the entire blockchain on the mist wallet?

I'm having an invalid date issue on mist. (https://github.com/ethereum/mist/issues/525) I'd like to just try to redownload the blockchain again. How can I do that ?
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Install Mist Ethereum on external HDD [duplicate]

The question is simple though I can't find a solution to this - how do I keep all ethereum-related files on an external hard disk drive? I would like to have the blockchain data, keystore and Mist ...
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How could I update default homesteadBlock value on my private Ethereum blockchain?

I am trying to create my private Ethereum blockchain with homesteadBlock value that I want to assign. As I understand default homesteadBlock value is 1500000. [Q] How could I assign homesteadBlock ...
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Distribution of KECCAK-256 hash values

Are values hashed using KECCAK - 256 uniformly distributed? If I use a KECCAK - 256 hash and then convert it to a number in a range 0 - N using the modulo operation, would the probability of obtaining ...
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1answer
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What is the cost of deploying contracts on Ethereum?

What is the cost of deploying contracts on Ethereum? What is the cost of deploying contracts on Ethereum? Intuitively, the cost should to be proportional to the size of the contract. How is the cost ...
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geth --fast sync extremely slow when run under systemd

I have dedicated an intel atom laptop with 2GB of memory and a 300+GB SSD as my ethereum node. I am running geth as systemd daemon. Now it's been running 3+ days day and night, with the command: ...
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1answer
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Does the EVM support garbage collection (reclaim unused memory)?

The EVM can reclaim storage by using the ‘delete’ keyword in Solidity. However, memory expands when more is allocated by the ‘new’ keyword, right? Are local variables also stored in memory? When ...
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does @ symbol has any significance in solidity?

In hyperledger when @ symbol is used in comments and it has its significance and is required before defining a function. I was going through some solidity code examples and I saw this piece of code /*...
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Parity create testing transactions and blocks

For test purposes, I would like to make test blocks including test transactions against main net. For example I would like to make a transaction that sends one ether from 0x1234567... to 0x99999999......
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Why immutable contracts [closed]

I'm a seasoned engineer, but quite new to blockchain technologies. I'm trying to grasp the "why" and the real "value" of immutable contracts. Never seen or heard of pieces of software being ...
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Is there a way to know the contract creation Address from a the transaction?

I know that in the transaction receipt I can get the contract address by getting a transaction receipt from a generated transaction. But I am wondering since smart contract addresses are ...
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1answer
250 views

Are uncle blocks unnecessary overhead on blockchain?

I have been learning about ethereum but now am stuck with conflicting thoughts about block times and stale blocks. Here is what I understood, please correct me if I am wrong. Block time for bitcoin - ...
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As of Feb 2016, how big is the ethereum blockchain size and its monthly growth rate? [duplicate]

As of Feb 2016, how big is the ethereum blockchain size and its monthly growth rate? Does the blockchain implement anything with pruning to reduce its size in the near future?
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If 2 transactions are included in the same block, which one is faster?

Suppose I have 2 transactions calling the same contract with a very high gas price, let's say 1000 gwei for tx a and 1001 gewi for tx b. If tx a is sent first before tx b, will tx b be faster to ...
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1answer
205 views

could not be able to change my setmessage because (Transaction has been reverted by the EVM:

I am working on react. As I have deployed my contract onto a specific address which have a following code: pragma solidity ^0.4.17; contract Lottery{ address public manager; address[] ...
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1answer
687 views

Is it possible to verify a given `block hash` is valid in a contract?

Inside my contract, I want to verify a given block hash is valid or not. block_hash_validation(string blockhash) returns (bool){ ...//check() return true; || return false; } Q1: If yes, from ...
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1answer
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How large is the blockchain?

I've been trying to download the blockchain for days now... My chaindata folder is currently at 12.5 GB...just how large is this blockchain?
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Dapp not conecting (through web3) when called from browser which dont have node running on it

trying to connect dapp through browser,when doing the same through the browser on machine which has running geth node is getting connect through public ip (eg :http175.xxx.xxx.xx:xxxxlogin) but the ...
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2answers
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what happens if there is a power cut while mining ethereum?

Does all your work go to waste or the mining continues from the last place you left. Lets say I am about to get a block solved and there is a power cut, how does it hamper my mining and the rewards.
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What are the differences between Bitcoin blockchain and Ethereum blockchain?

Ethereum has been debated in the bitcoin ecosystem and was criticized. In order to understand better both projects, what are the main differences between BTC and ETH regarding the blockchain ...
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1answer
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What would be needed to store the blockchain as a IPFS object?

In Christian Lundkvists blog post about possible uses for IPFS, he suggests that storing the Ethereum blockchain as an IPFS object could potentially decrease the size of the chain: We see the ...
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1answer
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Relationship between Transaction Trie and Receipts Trie

Reading through the Yellow paper, I can see that each block header includes the Keccak 256 hash of the root of the trie for transactions and transaction receipts. I am struggling to understand how and ...
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2answers
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How many transactions are there in a block?

If a block acts as a ledger of transactions, how many transactions can fit in a block? I have to setup a private test net where only one machine is allowed to mine while (many) others are performing ...
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How does data storage on the blockchain work?

If I store file chunks in the blocks, I'm causing duplicated blocks all over the networks (I mean, my file's chunks will be in each computer on the blockchain network, So eventually I have many many ...
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5answers
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What is a blockchain? What is the concept behind it? [closed]

I have been going through some docs, and I understand that BlockChains are mostly like the building blocks in an Ethereum network. So, can someone give a dumbed down explanation/definition about what ...
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How to estimate the cost to call a Smart Contract method?

After succesfully deployed this Smart Contract on Ethereum testnet https://testnet.etherscan.io/address/0x27c042342C9ba937214117e11A4970A6145034cB is it possible to calculate how much gas is going ...
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1answer
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What is the actual blockchain size? [duplicate]

I am trying to find the actual size of the etherum blockchain. I just found older posts that says it is around 21GB. What are the Ethereum disk space needs?
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1answer
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Geth Chaindata size [duplicate]

I did the blockchain sync from scratch via geth in command line. The current size of the chaindata folder is 68 GB. Is this normal or am I missing something. Also there is a .ethash folder with 66 GB ...
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1answer
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How to check if a transaction is still in the blockchain?

Say we want to confirm that a value transaction tx has reached certain finality, which we define as waiting for 12 block confirmations. We do this to drop the probability of tx getting lost due a fork ...
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1answer
267 views

Any understandable cryptography book/article/lecture to introduce to signatures, hashes, ECDSA etc..? [closed]

It's a long time I'm searching for cryptography lectures related to ethereum inside mechanisms, and everything I found has a high mathematical level. I'm an engineer, not a mathematics, so any article ...
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how to parse the Ethereum Blockchain and save the output to a file? geth console isn't node, right?

I'm trying to parse the Blockchain and extract to a txt file part of the transactions and Addresses to a specific contract (theDAO) for later analysis. I'd like to save the output to a file (.txt) in ...
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1answer
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Web3j: “Intrinsic gas too low” error when deploying contract in Ethereum from Java

I am a new to Ethereum and Blockchain, I have been trying execution of Contracts using Metamask and Remix using Chrome browser for sometime. I am trying to deploy the same contract from Java using ...
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2answers
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How much does it cost to store each IPFS hash in Ethereum blockchain

I've looked in some of the resource on calculating the Gas costs like this spreadsheet I found on this thread. But the spreadsheet only have computations gas costs but not storing of hashing. I'm a ...
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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
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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
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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
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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 --...
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1answer
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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 ...
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1answer
967 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
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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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2answers
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What is the order of operations to verify a transaction?

I am not asking if all nodes run each transaction. I'm asking for a rough time sequence of events. For example, in the case of a double spend attempt, and the double spender is colluding with the ...
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1answer
327 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
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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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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?
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1answer
648 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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1answer
880 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 ...
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1answer
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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 ...
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2answers
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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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1answer
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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; } ...