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26
votes
2answers
13k views

How many transactions can the network handle?

The voting on ethereum analysis by Dominik Schiener calculated that it would take 40 days to hold the UK general elections on the ethereum blockchain due to the transaction and gas limits. I redid ...
26
votes
1answer
4k views

When can BLOCKHASH be safely used for a random number? When would it be unsafe?

I've seen more complicated ways for a contract to generate a random number. But the Ethereum Yellow Paper itself suggests a "trivial solution" using the BLOCKHASH opcode (see below, bold is mine). ...
26
votes
4answers
5k views

what does `deploy.link` exactly do in `truffle`

Please explain use cases for deploy.link() function in migrations in truffle framework. How would you use it and for what.
26
votes
3answers
20k views

How to explore all transactions for a given account?

After beeing able to check account balances, I am looking for a method to list all transactions for a given Ethereum account through json-rpc protocol. I haven't found any method suitable for that on ...
25
votes
14answers
14k views

Truffle Webpack starts with error: MetaCoin has not been deployed to detected network

I seem to have followed the truffle guide to a T. But when I open my app in a browser for the first time, I'm getting this error in the console: Error: MetaCoin has not been deployed to detected ...
25
votes
4answers
4k views

Why does a Solidity throw consume all gas?

When you throw an exception, all gas is consumed. What is the rationale for this design decision?
25
votes
6answers
38k views

Is there a way to generate ethereum paper wallets?

Is it possible to store ether on paper wallets or generate printable private keys offline somehow?
25
votes
2answers
19k views

Can we get all elements stored in a mapping in the contract

Can we get all elements stored in a mapping in the contract using web3.js ?
25
votes
4answers
7k views

How to store IPFS hash using bytes?

Following Q/A (What datatype should I use for an IPFS address hash?) recommend us to use bytes to store IPFS hash. I was using following example(https://github.com/AdrianClv/ethereum-ipfs/blob/master/...
25
votes
3answers
15k views

Where is the state data stored?

This question was asked on Reddit a while ago: Where is the state data actually stored though? On the hard drive of each node? Separate from or within the blockchain? — Reddit: Basic ...
25
votes
6answers
4k views

What are common pitfalls or limitations when coding in Solidity?

What would be on your list to warn other developers about? What works in most other languages that does not work, or behave as expected, in Solidity? For example only: what parameters can be passed ...
25
votes
3answers
9k views

How does Solidity's sha3 / keccak256 hash uints?

This is not a question about the issue with Ethereum using a non-standard sha3. I have found the right JS hashing library, and am able to get matching hashes in JS and Solidity on byte strings. What I ...
25
votes
3answers
6k views

Can a contract safely rely on block.timestamp?

How safe is it to use block.timestamp as contract expiration time? If a miner provides an incorrect timestamp in a block header, how much can it be off before it is rejected by other nodes? Is there a ...
25
votes
3answers
17k views

Calling function from deployed contract

I want to know how to instantiate an existing contract deployed on the blockchain using its address. e.g: contract A { function f1() {} } A is deployed on the blockchain, and in contract B I ...
25
votes
4answers
7k views

What public test-networks and faucets exist?

What public test-networks exist and what are their conditions? What are the connection data? How often (if so) are they reset? Does a public faucet exist for this test network? Does a block explorer ...
25
votes
2answers
44k views

Why is my node synchronization stuck/extremely slow at block 2,306,843?

Using macOS 10.12.1 with Ethereum Wallet 0.8.7, nodes are connected but Sync doesn't even start. Stuck at block 2,306,843. What can I do? Please keep in mind, I am neither a coder nor a tech geek.
25
votes
2answers
19k views

What exactly is the Nothing-At-Stake problem?

What exactly is the Nothing-At-Stake problem in Proof-of-Stake consensus networks? While I understand what the nothing at stake problem means, I do not really understand the security implications. ...
25
votes
2answers
28k views

Ether Historical Prices

I am looking for historical datasets of the price of Ether. Similar to Bitcoin closing market price on blockchain.info or Coindesk OHLC dataset. Datasets in raw form are preferred (.json or .csv). ...
25
votes
3answers
10k views

What is a Shard?

Proof of Stake brings new concepts to the Blockchain ecosystem. In the dictionary "Shard" is defined as "A broken piece or fragment, as of pottery or glass".
25
votes
2answers
9k views

Can I save structs in a Mapping?

Is it possible to store structs in a Mapping or any dynamic memory structure in my Solidity SmartContract?
25
votes
1answer
30k views

Geth node starts to sync from the beginning after fast sync

I have synced using the --fast command. Now how should I proceed? I tried stopping it, and then running geth --rpc but it says: Last Header #1311471 Last Block #0 Fast Block #1310224 What should I ...
25
votes
1answer
20k views

What are the valuable benefits of having a node?

Supposedly I'd like to help Ethereum to expand (in terms of the World Computer), so I'd like to setup a Linux machine which can run smart contracts. What kind of benefits I can get from doing that? ...
25
votes
1answer
8k views

How to unit test smart contracts

How are Ethereum contracts tested? I've seen Truffle which referrers to itself as an Ethereum development framework. Are there any other frameworks and what is their level of maturity? Is there a de ...
25
votes
3answers
3k views

What is the exact “longest chain” rule implemented in the Ethereum “Homestead” protocol?

This paper from 2016 claims (in section 3.3.2, speaking about the actual Ethereum implementation as opposed to the specification) that: although uncle blocks that are included in a block receive a ...
25
votes
2answers
16k views

When will the difficulty bomb make mining impossible?

I know the answer must be out there in the code already, but I couldn't figure out where exactly. Could someone do the maths for me: With block 200k the difficulty bomb started increasing the ...
25
votes
3answers
8k views

Are there any public/free nodes to connect a Dapp front end?

I have a small Dapp written in Meteor (client only) that reads some contract and account info from the blockchain. I can deploy my front-end code for free on meteor.com (or a variety of other places),...
25
votes
1answer
5k views

What is the “difficulty bomb” and what is the goal of it?

The difficulty bomb is related to the switch to proof of stake. How does it work exactly and why is it going to help to switch to proof of stake?
25
votes
1answer
12k views

Ethereum ecrecover signature verification and encryption

The question of signing and verifying signatures with Solidity has been asked in these questions, both of which I have tried to study: How can I sign a piece of data with the private key of an ...
24
votes
8answers
33k views

How do I get the raw private key from my Mist keystore file?

I use the Mist wallet. I would like to know: How I can get the private key of my account. How I can use this private key to sign messages.
24
votes
3answers
24k views

How to get return values when function with argument is called?

I am writing below a simple contract which stores all results of questionnaires for each ID. contract answer{ mapping(address => mapping(string => bool)) voters; struct qList { uint ...
24
votes
3answers
20k views

How can I expose Geth's RPC server to external connections?

I want to set up a private network of applications which can connect to a single Geth node. What options do I have for exposing the RPC server? I'm running this: geth --rpc --testnet (sometimes I use ...
24
votes
3answers
12k views

Is it possible to cancel a transaction?

Is it possible to cancel a transaction broadcast to the blockchain? Suppose I broadcast a transaction and want to cancel it before it has been mined. Is this possible? This could be useful on ...
24
votes
3answers
7k views

How many nodes are there on the Ethereum network?

When looking on the Ethereum Network Status site, only a limited number of nodes are listed. How can I discover how many nodes there are currently running in total?
24
votes
6answers
13k views

Truffle deployment on test network says: Error: exceeds block gas limit

I'm trying to deploy a sample contract (following this guide) but I'm receiving an error of not enough gas. I changed the numbers a little but could not fix it. I saw this question in stack exchange ...
24
votes
1answer
6k 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
2answers
78k views

What's the best hardware for Mining Ether?

As my title says, I am a complete newbie to the Ethereum Project, but not to the cryptography in general. Although this will be the first time I will consider investing in the mining process. And I ...
24
votes
2answers
4k views

What is the merit of creating new smart contract languages like Solidity instead of using other languages?

What is the pros and cons of creating new languages like Solidity for smart contracts instead of using other computer languages like Golang or Python?
24
votes
4answers
14k views

Why is ether divisible to 18 decimal places?

1 ether is 10^18 wei, the smallest denomination. Why does ether have such a high degree of divisibility?
24
votes
2answers
27k views

What is Ethereum's inflation rate? (how quickly will new ether be created)

It seems like the answer is still in flux, but it would be nice to have a single answer to this question that we can update over time.
24
votes
5answers
17k views

Paying a transaction fee with an ERC20 token

As far as I understand, one of the ERC20 token's features is that you can pay a transaction fee with it. In other words, you can send them without having Ether. I transferred REP tokens to the ...
24
votes
1answer
2k views

How does the solidity optimizer work?

The compiler for solidity supports the flag --optimize which performs some set of optimizations to the compiled solidity code, typically resulting in a reduction of gas costs. How does the optimizer ...
24
votes
1answer
15k views

Stack too deep, try removing local variables [duplicate]

When I set more than eight values as function’s return , the following error occurred. ( When the num of values is less than seven, the error didn’t occur) Could you tell me how can I get more than ...
23
votes
6answers
31k views

Insufficient funds for gas * price + value

Sending Address has over 1 Eth in current Balance. Using the Geth console, I can send many transactions of any amount less than .033 eth.sendTransaction({to:'...
23
votes
4answers
16k views

How can I empty the blockchain?

I am trying to do a fast sync using geth --fast but I am getting this message: blockchain not empty, fast sync disabled How can I empty the blockchain to allow for fast sync?
23
votes
1answer
8k views

What is Parity's “warp” sync, and why is it faster than Geth “fast”?

A follow-up of one of the classic questions on this site: One of the answers to this question suggested using Geth's --fast flag to help quickly synchronise the block data. Now, parity comes with ...
22
votes
5answers
27k views

How do you stop a running geth node?

I can not figure out how to stop a running geth node without killing the process. I tried to lookup geth help but there is no mention of stopping, halting or any shutdown command. How to shutdown ...
22
votes
5answers
18k views

How can I return struct when function is called?

I'd like to return struct type User. However, when I tried the following getUser function, it returns an error. Is there any way that struct data would be returned from a function? Contract struct ...
22
votes
4answers
19k views

Is the block.timestamp value in Solidity seconds or milliseconds?

I'm looking to use block.timestamp in one of my contracts and I want to know whether the block.timestamp is seconds like in Python or milliseconds like in Java or some other value? Also, is it safe ...
22
votes
5answers
7k views

Truffle configuration file name - is it 'truffle.js' or 'truffle-config.js'?

Truffle configuration file is mentioned in several places on the web (GitHub, truffle package on npm, solidity-coverage package on npm, etc.). Some refer to it as 'truffle.js, others refer to it as ...
22
votes
3answers
5k views

How to add new Sealer in Geth 1.6 Proof of Authority?

Hi there Ethereum experts, I'm trying out Proof-of-Authority in Geth 1.6 for my private network and got it to work on a few nodes using Puppeth. Now, I have two questions about maintain the private ...

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