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13
votes
1answer
1k views

How do I get the storage indices/keys?

I would like to explore the storage data of a contract. I have geth fully synched and I interact with it over RPC. There is the function "eth.getStorageAt(addr, index, block)" provided, but you need ...
11
votes
1answer
2k views

Is it possible to change the block target time?

We're curious to know what factors go into block times in a private network with a limited number of validators. Is this fixed or can it be parameterized in any way? How is it related to block times ...
8
votes
1answer
2k views

Iterating over all public values of a mapping in web3

Let's assume we have the standard token contract with balances: mapping (address => uint256) public balanceOf; If I want to know balances of all addresses (who have ever transacted with the ...
7
votes
2answers
3k views

Syntax for calling contract state changing methods

I've been struggling a bit with calling methods that change the state of the contract. Take, for example, the following contract: contract C { uint[] numbers; function initNumbers() { ...
7
votes
1answer
1k views

How is contract storage arranged?

Thinking about smart contract storage, how is the data arranged? I know that every variable within a contract has an unique ID, therefore, it's possible to create a node with a structure like <...
7
votes
2answers
2k views

Who gets the fee from contract call?

Basically you don't need to pay fee for contract call, but if a contract method does lots of work, you need to add gas in contract call to prevent DoS attack like this: contract.method.call({gas: ...
6
votes
2answers
1k views

Are mineable tokens possible?

I'm a bit puzzled about the ethereum.org/token example which states further down in the advanced examples that it can be coupled to proof-of-work. I really like the idea of mining a token. The example ...
17
votes
3answers
24k views

Unlocking accounts and making transactions in web3.js

This question is related to this one and this one. It also has a partial answer here and here. In the third link the account is being unlocked for a period of time using web3.js: web3.personal....
11
votes
2answers
1k views

Does Ethereum have a replace by fee option similar to Bitcoin?

If I send an Ethereum transaction that has not yet been confirmed by the network can I rebroadcast the same transaction with a higher fee and a new destination address?
10
votes
1answer
764 views

How can I reliably induce a blockchain fork for testing purposes?

I would like to reliably induce a fork on a private testnet so that I can test the behavior of off-blockchain code that interacts with contracts. (see related questions as to why I would want to do ...
10
votes
1answer
1k views

Bytecode on block chain different from the one used when deploying

When I deploy a contract from node.js using the web3 JavaScript API (connected to a locally running geth), and then check the deployed bytecode using eth.getCode(address) (either from the JS console ...
7
votes
1answer
1k views

How to call Library Function from a Contract? => [error] The contract code couldn't be stored, please check your gas amount. undefined

When I compiled following code at "https://ethereum.github.io/browser-solidity/" it gives me two Web3 deploy code for: var libraryContract = web3.eth.contract(...); //Web3 deploy code var ...
7
votes
1answer
5k views

How to unlock accounts programmatically after the node has started?

Is there any way of just unlocking accounts without opening the console with geth? I'm writing some scripts to automate cluster generation and I wish I could just call geth to unlocking some accounts ...
7
votes
2answers
7k views

How to verify token after etherscan, and submit icon

Sorry, my English is not good, I verified my token on etherscan, but I do not know how to change the token's icon.
15
votes
2answers
10k views

How much faster is it to sync with --jitvm?

geth help has: VIRTUAL MACHINE OPTIONS: --jitvm Enable the JIT VM The impact of --jitvm has been unanswered and I'm looking for answers to these 3 specifically: How much faster is geth ...
9
votes
2answers
608 views

What is the measured distribution of block times since Homestead?

The variance of block times should arguably follow a Poisson distribution. But by casual observation I've seen blocks fast as 4 s or 1 m 15 s. The average is around 14 s since Homestead. If it follows ...
8
votes
1answer
2k views

How do I tell whether the Mist/Wallet is “fast” or “full” syncing?

I'm currently installing Mist/Ethereum Wallet from the pre-built binaries. Having the run the ./Ethereum-wallet executable, it's now part-way through syncing the blockchain. It seems to be taking ...
8
votes
2answers
6k views

How to recover BTC that wasn't converted into ETH by Shifty via Mist?

I tried the "deposit with BTC" option BTC transfer was recognized in "Awaiting Deposit" Then "Awaiting Exchange" timed out, I got a "try again" dialog, and was shown no way to get my BTC back or to ...
8
votes
2answers
1k views

Are Transactions originating from one account mined in nonce order?

Discussion in another thread raises an interesting point. how many transactions could be included in a new block from the same account? Since miners can opt to omit a known transaction from the ...
5
votes
1answer
964 views

How to replicate Bitcoin's OP_RETURN functionality on Ethereum?

I know Ethereum is more advanced, and allows for more interesting things than associating data to a transaction. But let's say I have a legacy system that uses Bitcoin's OP_RETURN. What options do I ...
3
votes
3answers
2k views

How to recover my ether.li wallet with any other wallet software?

I am facing the following problem with my ether.li wallet, I never had Problems in the past with sending transactions but for the last two days transactions stopped working for me. Whenever I try to ...
3
votes
1answer
456 views

Is gas price paid by the transaction sender to the miner, or the miner reward is newly generated?

A sender of transaction can specify the gas price it is willing to pay for the transaction. Also, if there are no transactions, miners mine empty blocks and still get rewarded with newly generated ...
2
votes
2answers
5k views

How to Fix “Stack Too Deep” Error?

I know that this has been covered in other questions here but I'm not sure what's happening in my case. My code is returning a compiler error "Stack too deep, try removing local variables." But I only ...
15
votes
1answer
3k views

How Can I Add My Name Next To Address On Etherscan?

I'm wanting to set up a charity and want to use a public wallet for accepting donations with on Etherscan where I can have a displayed name next to the wallet like this: How Can I Add My Name Next To ...
6
votes
2answers
774 views

Why does an empty message still invoke the code of the contract?

An empty message still invokes the code of the contract and is the mechanism that allows Solidity to implement a feature of a fallback function per contract. But when msg.data is empty, why does ...
5
votes
1answer
4k views

How do I get a refund for my The DAO tokens that was split into a child DAO?

The DAO token holders that split away from the main The DAO into a child DAO will have moved the tokens (DAO) and the corresponding ethers (ETH) into the child DAO. As these DAO token holders have a ...
14
votes
5answers
32k views

Where can I find some Solidity / Smart Contract source code examples? [closed]

Is there an easy to access list of Solidity / Smart Contracts / Dapps source code examples? Related information: Is there a list of DAPPS that are already useable? Where can I learn how to develop ...
87
votes
5answers
41k views

What is the difference between Swarm and IPFS?

IPFS seems a little slow on existing dapps. will Swarm load content more quickly? Also- is there a roadmap for swarm?
52
votes
4answers
29k views

What proof of work function does Ethereum use?

The Ethereum frontier network currently uses a proof of work (PoW) based consensus algorithm. But which specific PoW function does that algorithm use, and why was it chosen?
27
votes
3answers
11k views

Ethereum Merkle Tree Explanation

Here is my basic understanding about how Ethereum stores transactions A hash is generated for each transaction Then pairs are selected and a hash is generated for each pair This way the last ...
28
votes
4answers
23k views

How can I run go-ethereum as daemon process on Ubuntu?

The Installation Instructions for Ubuntu suggest running geth from the command line, how can I run it as daemon process / service on Ubuntu?
46
votes
4answers
11k views

Is there anything stopping me from using the ethereum blockchain as data storage?

As I understand it, smart contracts are currently immortal by default. Does this mean that I could create a contract that happened to contain an encoded form of baby photos and have it stored forever? ...
21
votes
1answer
5k views

How does Ethereum make use of bloom filters?

As stated in the yellow paper: Transaction Receipt. In order to encode information about a transaction concerning which it may be useful to form a zero-knowledge proof, or index and search, we ...
24
votes
1answer
9k views

Is there a table of EVM instructions and their gas costs?

The EVM instructions are in the yellow paper, or they are summed up in this answer. But their gas costs are not there. Where can I find a list of all instructions with their associated gas costs?
34
votes
2answers
27k views

Is Ethereum wallet address case sensitive?

I sent some amount of ETH to a wallet. I checked the wallets balance on ether chain. I entered the address in the search field and noticed both lowercase and uppercase versions of the address seemed ...
28
votes
5answers
18k views

How to access the event log by knowing the contract address (web3)?

How can I access a log stored in one of the tx of the contract via web3? Code example: event newtest(string indexed name, uint indexed idlevel,string indexed multib, string objmulti, uint objnm); ...
24
votes
5answers
14k views

web3: How do I get past events of myContract.myEvent?

I use the following JS code to get notified of Solidity events and it works well for incoming new events: myContract.myEvent().watch((error, result) => { if (error) console.log('Error in ...
3
votes
1answer
5k views

What is the difference between a private key, password, brain wallet, recovery passphrase, and wallet?

What is the difference between a private key, password, brain wallet, recovery passphrase, and wallet, if any? Is there any connection between these?
15
votes
4answers
18k views

Possible to store the blockchain in a different directory?

I'm running geth on Linux within a Chromebook. The blockchain is being stored within ~/.ethereum, along with other important files. Problem is, the storage capacity on my Chromebook is quite limited ...
13
votes
5answers
27k views

Deploy contract from NodeJS using web3

I'm trying to create and deploy a smart contract through NodeJS using web3, but it is not working as I get a "web3.eth.contract.new is not a function". Here is my code: var web3 = require('ethereum....
24
votes
1answer
13k views

How does the delegatecall method work to call to another contract's method?

I'm trying to figure out how to use the delegatecall method on a contract address in a contract to call a function in a separate contract. I know Libraries are the higher level interface to use but I ...
18
votes
2answers
7k views

What are the types of nodes in Ethereum?

I have seen the usage of the word full node many times. What exactly is an Ethereum full node? What are bootstrap nodes and light nodes/clients? Are there any other types of nodes?
18
votes
2answers
3k views

Explanation of Parity Library Suicide

So today, A vulnerability found within the Parity walletLibrary which resulted in freezings of potentially hundreds of millions of dollars from wallets using parity multi-sig. Can someone technically ...
14
votes
1answer
4k views

Deploying contract with constructor arguments via Geth RPC

How can I deploy a compiled contract with constructor arguments using geth rpc? I have tested my call deployed the compiled contract bytecode just fine, I just don't understand how I can pass ...
9
votes
5answers
6k views

How to convert an address to bytes in Solidity?

What is the recommended way to convert an address to bytes in Solidity?
28
votes
3answers
3k views

What was the reason to invent the EVM?

What was the reason to invent the Ethereum Virtual Machine (EVM)? Why not use an existing virtual machine like the Java-VM. The big advantage would be that the existing toolsets for Java development ...
15
votes
2answers
4k views

Is there a maximum number of entries for a mapping?

In many contracts, notably voting, there is a mapping of the kind mapping(address => bool) voted; How many voters can be registered in that way? is there a size limit? will the contract need more ...
13
votes
3answers
3k views

What are State Channels and use case/code examples?

A previous Reddit post gave some indication: It's basically Lightning-network style payment channels but for arbitrary state updates. Participants in the Dapp send messages with transactions to ...
9
votes
2answers
3k views

how to use ethereumjs-tx.js in a browser

I have been trying to use ethereumjs-tx in a browser. I have downloaded the browser builds from here https://github.com/ethereumjs/browser-builds/tree/master/dist This is my code snippet <head>...
8
votes
1answer
720 views

Getting complete state of a smart contract

From the yellow paper, I figured out that a contract has 4 components 1. nonce, 2. balance, 3. code, 4. storage. To know about the current state of a smart contract we need to know the all these ...

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