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11
votes
4answers
1k views

“potential rewrite attack” message on Geth

When I was sending Ether using Mist I got the following message on Geth. I0528 18:34:57.312997 core/blockchain.go:959] imported 1 block(s) (0 queued 0 ignored) including 3 txs in 19.344963ms. #...
11
votes
0answers
474 views

Guidelines for designing contracts to handle bugfixes? [duplicate]

Most introductory guides for contract design talk about creating "mortal" contracts (contracts that include some function that triggers a suicide() call), but what about if that contract was for some ...
9
votes
5answers
16k views

Is there API to create Ether wallet?

I know how to create wallet manually, however I would not like to take my clients out of website (I doubt anyone would) and would rather do their wallet creation behind the scenes when they register ...
9
votes
1answer
625 views

What data will zk-SNARKs protect?

Implementing zk-SNARKs is planned in Ethereum roadmap, what data will be obfuscated? transaction sender and receiver? data in transactions? data stored in contracts? variables and methods in ...
8
votes
1answer
870 views

Give a summary of the fork state changes in block 1920000

The hard fork during block 1920000 contained the execution of an irregular state change. For reference purposes it would be great to have a technical overview of these changes and how they were ...
8
votes
1answer
422 views

What is the cryptic part at the end of a solidity contract bytecode?

Given the following contract: pragma solidity ^0.4.11; contract Simple { bytes32 public v; function set(bytes32 _v) { v = _v; } } When disassembling, neither remix, solc or evm ...
6
votes
3answers
2k views

How can I modify bytes32 result to uint?

I want to separate three last digits of the most recent block header hash and get the result as uint. I can get the answer as bytes32 by this code, but how can I change this result to uint? contract ...
6
votes
1answer
2k views

How does a fallback function rejecting ether work?

A contract in Solidity can have a fallback function like: // This contract rejects any Ether sent to it. It is good // practise to include such a function for every contract // in order not to loose ...
4
votes
3answers
1k views

How to recover EtherLi Multi-Sig Wallet without SMS?

For any reason is phone number in my EtherLi Multi-sig wallet settings wrong. I don't receive the 2nd verification code by SMS due to the wrong digit in my phone number. Please let me know how to ...
3
votes
1answer
1k views

How to fork Ethereum from the current state?

I've read a lot of tutorials and guides that teach how to set up your own private network from scratch. However, how would I do that from the current state of the blockchain? Instead of generating a ...
1
vote
2answers
2k views

How to import account form geth console to metamask (private blockchain)

I want to import accounts from geth console(private network) but I can't. I have UTC file when I create account with geth but when I open file and copy mac and paste to metamask (private key) account ...
14
votes
1answer
3k views

What happens if transaction runs out of gas before transaction completes?

As gas cost can only be estimated until the transaction is executed against the actual contract state at the time of execution on the blockchain, what happens if transaction runs out of gas before the ...
11
votes
5answers
122k views

Cannot allocate big buffer - Not enough graphics memory?

I am using Claymore's Dual Ethereum v9.5 Here is my config file: setx GPU_FORCE_64BIT_PTR 0 setx GPU_MAX_HEAP_SIZE 100 setx GPU_USE_SYNC_OBJECTS 1 setx GPU_MAX_ALLOC_PERCENT 100 setx ...
9
votes
1answer
2k views

Custom balance accounts testrpc?

I am setting up unit tests with for my contracts using truffle. I am using also testrpc, but having accounts with 2.123...... *10^37 Wei is not very helpful to visualise and debug things. I am trying ...
9
votes
1answer
3k views

How to send ether to a cold storage account?

Is it possible to do the following: Back up the keystore on a usb drive. Format the computer used to generate the keystore. Send ether to a public address in the keystore. Reinstall geth (or other ...
7
votes
1answer
2k views

Default Value for gas in sendTransaction

What is the default value for gas in sendTransaction api? Suppose I don't specify gas parameter in the sendTransaction api, what will be used? Also, will this vary if it is a contract transaction ...
7
votes
1answer
3k views

Will a GPU help with Proof-of-Stake?

Will a GPU be required to do proof of stake as a full node? Will it help me be more profitable? Will a highly available network connection be worth more than having a beefy GPU? What if I don't stay ...
4
votes
1answer
2k views

Not syncing due to “unhandled trie error: missing trie node”

Having an issue. Was caused by Avast blocking a file after I sent some Ether to Dao. Have removed Avast now that I understand it was messing stuff up. Restarted computer... now when i try to sync it ...
3
votes
1answer
2k views

Does my mining situation sound normal?

I've tried overnight mining and have had no luck. I first created an account using geth account new. Then I use geth --rpc to stay in sync with the blockchain and ethereum -G to start the minining ...
3
votes
1answer
4k views

How long to wait for pending transactions?

Is there any timeout for pending transactions? How long to wait before re-sending the transaction. I am sending multiple transactions and need to track the status of all those transactions. But I am ...
3
votes
2answers
507 views

Would a minimal gas price tx ever be mined?

I want to mine and charge a minimal gas price (like the minimum required to prevent infinite loops and such), to enable many smaller transactions to be confirmed super cheaply and to lower the cost of ...
3
votes
1answer
518 views

I need help with signatures

So, for my studies, I am supposed to interact with a contract function that has the following built in condition: if (ecrecover(_h, _v, _r, _s) == msg.sender && _h == sha3(this)) I am ...
2
votes
1answer
3k views

Which miner gets the gas fee for each transaction? [duplicate]

I'm guessing that miners are randomly selected, but I'm curious as to which miner receives the fee for gas paid for each transaction? In hindsight, the answer to this question is obvious: of course ...
1
vote
2answers
2k views

Should signed text messages use the “\x19Ethereum Signed Message” prefix?

Background: I want to implement sign message feature in Trezor. Is there a standard for signing text messages? So far I found out that etherscan.io signs messages without the prefix, i.e. it signs ...
101
votes
2answers
18k views

`external` vs `public` best practices

Apart from the public modifier Ethereum introduces the external one. Both may be called outside of the contract and inside (the later one by this.f() pattern). Moreover, according to the docs: ...
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 ...
20
votes
2answers
17k 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 ?
32
votes
2answers
20k views

Solidity, create contract from contract

Based on documentation it should be possible to create new contract from contract contractAddress = new OwnedToken(name); When I invoke this method from contract, the address I receive seems to be ...
24
votes
2answers
18k 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. ...
24
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 ...
11
votes
6answers
18k views

Better pattern to detect web3 default account when using metamask

Context: I want to use blockies to render an identicon on the page, i get the defaultAccount from web3, for this, the user has to be logged on to metamask with a selected address from his wallet. The ...
64
votes
2answers
49k views

What is the relationship between Mist and Ethereum Wallet?

In https://github.com/ethereum/mist/releases 0.3.6 the files are named Mist. Starting in 0.3.7 the files are named Ethereum-Wallet. Will files named Mist take over in the future, or will there be 2 ...
31
votes
2answers
4k views

Do contracts also have a nonce?

Do contracts also have a nonce and if so how is it calculated? Usual accounts have a nonce that is increased with every transaction. However, contracts can't make transactions, they can only make ...
13
votes
6answers
17k views

Is there a list of DAPPS that are already useable? [closed]

Is there a list of DAPPs that are already useable? Useable means there is an easy accessible GUI, that can interact with the contract.
25
votes
6answers
37k 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?
28
votes
3answers
10k views

What are truffle migrations?

As written in Truffle docs: Migrations are Javascript files that help you deploy contracts to the Ethereum network. These files are responsible for staging your deployment tasks, and they're ...
14
votes
1answer
4k views

How can I create a listener for new transaction with Ethereum RPC calls?

I am trying to create mini-service which would allow me to subscribe for incoming Ethereum transactions (coinbase example). I thought that in Ethereum it could be done with eth_newFilter and ...
9
votes
1answer
3k views

How to steal eth using delegatecall and selfdestruct

This documentation says Even if a contract’s code does not contain a call to selfdestruct, it can still perform that operation using delegatecall or callcode. This worries me. I've created ...
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 ...
18
votes
6answers
25k views

How to decode input data from a transaction?

I'm sending a transaction to an account with some data with the following command: eth.sendTransaction({from:eth.accounts[0],to:eth.accounts[1],value:web3.toWei(1,"ether"),data:web3.toHex("http://...
23
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?
18
votes
3answers
17k views

Solidity: Can you return dynamic arrays in a function?

I know I can return dynamic byte arrays in Solidity, such as in the following code: function createMemoryArray(uint size) returns (bytes) { // Dynamic memory arrays are created using `new`: ...
16
votes
3answers
10k views

What's the proper way to wait for a transaction to be mined and get the results? [duplicate]

I'm using react to write the frontend for my dApp, and doing this to (attempt to) update react's state via an asynchronous sendTransaction call: var thisJS = this web3.eth.sendTransaction({from: ...
16
votes
1answer
3k views

What is state-trie pruning and how does it work?

Several sources mention the idea of state-trie pruning. What is that, and is it currently being implemented on the network? Is this a manual process or can it be done automatically? If Ethereum is ...
28
votes
3answers
6k views

What is the difference between transaction cost and execution cost in remix?

What is the difference between transaction cost and execution cost as seen after contract instantiation in remix? I don't think it matters, but here is my contract: contract DepositCounter { ...
20
votes
1answer
10k views

Initialising structs to storage variables

The following code fails to compile with error: Type struct SomeStruct memory is not implicitly convertible to expected type struct SomeStruct storage pointer. contract StructExample { struct ...
20
votes
2answers
3k views

Why are there no leading zeroes in ethereum block hash?

The block hash has to be below certain difficulty, right? In bitcoin this means, that there are many leading zeroes in hash value, eg. for bitcoin block #402329 hash is ...
19
votes
5answers
37k views

How to know if a transaction went through or not? (out of gas)

Apparently when sending transactions from an Account instead of a Wallet, the gas spent is small (21K), and not enough to send ether to a Contract Wallet (out of gas, so to speak). When this happens, ...
15
votes
6answers
10k views

How can dapps work on smartphones?

How can dapps on mobile web browsers interact with web3.js? Is there any tool like Metamask or Mist on the roadmap for mobile?
10
votes
2answers
6k views

Adding private network peers to Parity

If possible, I would like to use parity with my private ethereum network. This answer (https://ethereum.stackexchange.com/a/9148/4575) provides us a solution that geth will run on the background and ...

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