All Questions

We know there is an option to add a block reward contract to incentivize authors of new block by using blockRewardContractAddress at chain engine specs. Is it possible to add this property in the ...

I'm trying to send 12 integer as bytes to a contract function. If I use web3.utils.toHex(12) the variable will become 0xc The problem is that when contract function parses bytes, it reads uint256, ...

I've launched a geth client over IPC: geth --dev --allow-insecure-unlock --ipcpath ipc://$HOME/Library/Ethereum/geth.ipc And trying to connect using a Web3 IPC provider: my_provider = Web3....

Inside a DAPP, I have been using web3.currentProvider.publicConfigStore.on('update',... to monitoring Metamask activity. But in the new metamask-mobile such method does not exists. There is a ...

I have deployed ERC20 with reference to // File: openzeppelin- zos/contracts/token/ERC20/DetailedMintableToken.sol I called the initialized function with owner, name, symbol and decimal value. ...

I have follow this SO answer for sending ERC20 tokens from 1 address to another. I am running into an issue where I am receiving an error that my from address is invalid Error: Error: ...

I am working on a Solidity Smart Contract (^0.5.10) where I want to return an array of Ratings elements. struct Ratings { address restaurant uint8 score }; Since returning Rating[], string[]...

I want to create a smart contract that users can send a number to and receive an amount of ether. function airdrop(uint val) public payable { require(airdrop == true); if (val == 0x31){ ...

I'm trying to recreate this site TenThousandSu And this is the smart contract I'm trying to call https://rinkeby.etherscan.io/address/0x7e338acfb7a5d7e99f4225cc12dc884f49c00f6a#code I'm using "1.0....

What is the maximum size of the IPC file in ethereum? Are there any way to increase its size?

I'm currently working with bytes in Remix. The goal I wanted to achieve was to put variables into bytes in one function, copy bytes, paste bytes to another function as a parameter and unpack these ...

I'm using Provable for getting a random number and I am using following code snippet from their github: https://github.com/provable-things/ethereum-examples/blob/master/solidity/random-datasource/...

I'm looking here: https://web3js.readthedocs.io/en/v1.2.0/web3-eth-personal.html#providers This works fine for me, however I'm wondering how to specify things like timeout and other networks ...

Do you know why a single address of type contract is mining 38% of 0xbtc? Does it mean that a single person has find a way to mine as much 0xbtc as a whole mining pool? Plus how come a contract is ...

Is it possible to access the length of an enum in solidity? E.g. pragma solidity >=0.4.16 <0.6.0; contract test { enum ActionChoices { GoLeft, GoRight, GoStraight, SitStill } function ...

I have a library which contains a function concat - it can merge two bytes. I have deployed a contract which uses that library and it works. I would like to make a simple bytes builder on my website. ...

Is it possible to have a mapping inside a struct for vyper? For example: struct Teddy: id: uint256 year: uint256 component: map(uint256, uint256) teddies: private(map(uint256, Teddy)) ...

I know this question has been already asked many times, but I haven't got any satisfiable answer and so asking here. I want to create an Authentication system dApp using reactjs. The user is having ...

I read that smart contracts don’t have a private key, so they can’t sign a transaction. My question is: when a smart contract starts a transaction to an EOA, how are we sure that the smart contract ...

How can they be used with solc?

From the solidity docs: If you use pragma experimental SMTChecker;, then you get additional safety warnings which are obtained by querying an SMT solver. The component does not yet support all ...

I managed to deploy a token contract with interface on Kovan Testnet. Now I wanted to verify the code. However this is a bigger problem than I thought. The contract got successfully deployed to: ...

I have seen people use both memory and calldata keywords when writing Solidity. Specifically, they are used when declaring function parameters. When should I use memory and when should I use calldata?...

I am trying to embark on getting all the contract addresses pulled from the Ethereum blockchain. From what I read, a fast node is all that is required for this (getting blocks->txns->contractAddress ...

I'm using the Web3 library. I want to extract a signature hash from a Web3 transaction to send to an external hardware device, sign it there, then use the signature I get from there to broadcast my ...

Would this be a non-malleable way to generate numbers for my particular use case? Let me explain: I allow people to register for a lottery-type event. If a winning seed belongs to their ticket set, ...

I have 3 solidity smart contracts that run in a quorum network with 7 nodes. At the moment i use the constructor to set the owner of the smart contract, that is the node that deployed it. ...

Please look at my simple example below. Is migration script 3 being executed, such that it sets the value on the blockchain -- I think not, because there is no speak about a txHash or cost... How to ...

From the solidity docs on contract metadata: You have to publish the metadata file to Swarm (or another service) so that others can access it. You create the file by using the solc --metadata ...

I have a smart contract that keeps record of the people holding the tokens in form of array of addresses. An owner of the smart contract, whenever, sends some ethers to the contract these ethers shall ...

Want to deploy and operate a Decentralized Autonomous Organization (DAO) on Ethereum. What are my options?

I've gone through various Blockchain Tutorials but everywhere it's one or the other same thing. Download truffle/ganache, from 10 free testrpc account, use one, use metamask, Remix IDE etc, and Voila!...

I had wallet from 2016, but i'm forget password login by keystore. Current i just had keystore, how i can get private key or password keystore? Thank so much

I have referred, Web3 Events, but filters object is not working for me, I've got the same result for events before and after applying filter object. Here's the code: instance.getPastEvents( "...

I'm trying to test making some smart-contract that uses DAI ERC20 tokens on Kovan testnet (DAI contract on kovan is 0xc4375b7de8af5a38a93548eb8453a498222c4ff2). I developed this very simple contract ...

Already referred web3 documentations and other Q-A for web socket connection. Currently using infura as provider.

Is it possible to create many ERC721 tokens at a time? I saw this link. ERC721 - Create 1000 tokens in one function call But I don't get it. Please help me.

Can I trigger a smart contract on specific date? If I deploy a contract today and I want execute some function of that contract tomorrow without any exteral intervention. Is it possible?

I have followed Web3 documentation to subscribe an evnet, I have created Instance of web3 using infura url as argument. Created contract object using, const contract = web3.eth.contract(abi, ...

Smart contracts can obviously send transactions through the Ethereum network but can they also send a simple message along with the transaction? Usaully you would put the message into hex code in the ...

I am currently developing a dApp with Drizzle on top of ReactJS. My project consists of, basically, 8 .sol files. 4 of them are just abstract contracts that include the functions, structs etc. for ...

The words in the stack are 256-bit, therefore 32 bytes in hexadecimal representation. The Ethereum Yellow Paper states “the stack as a size of 1024”, although it does not say what (bits/words). A ...

Say I want to reference another smart contract in my smart contract. Do smart contracts have an identifier (like a number 0xjdjdjdjdjjddj etc.)? And if they don't, how would you reference a ...

I am developing a large database of exploitable contract addresses and creating a website to host such a database for users to use to see if contracts are safe. Is there a way to get all contract ...

Does a transaction that requires the entire block gas limit to be executed (currently ~8M) take the entire block by itself? And if that's true, will that transaction take longer to get confirmed than ...

What is the best way to get balance and send ERC-20 token using web3j?

I'm trying to deploy a truffle project to testnet. When I run truffle migrate --reset --network rinkeby --verbose-rpc, this is output: You can improve web3's peformance when running Node.js versions ...

can i deploy a private network like the way it does other private blockchains with Ethereum ? and the test networks in Ethereum only work for public right or can i deploy it there ?

Assume that reward policy of Ethereum is changed from 3eth to 1eth. Hard fork is ongoing but, there are miners who don't consider updating their software. what happens? The miner who did update ...

How to build the bridge between two different consensus blockchain platform? use case: 1.we need to ensure visibility of the transaction in both platforms to assure its integrity When a smart ...