All Questions

0
votes
2answers
23 views

Finding a better way to retrieve information about struct

I've run into a problem about getting information about the structs. The code is written below: pragma solidity ^0.4.23; contract Transport { address public manager; Batch[] public ...
0
votes
0answers
8 views

Get full name of keystore file after creating it

After creating a keystore by this code ks := keystore.NewKeyStore("./tmp", keystore.StandardScryptN, keystore.StandardScryptP) password := "secret" account, err := ks.NewAccount(password) ...
0
votes
1answer
14 views

Accessing MEW with Trezor One not working

I have been unable to access MEW using my Trezor One, when I click on Ether on the Trezor wallet page, it throws me into an unending loop back to the "How do you want to access your My Ether Wallet", ...
0
votes
0answers
14 views

How to instatinate and test Registry/Logic contracts with Geth?

I am having troubles getting below contracts tested with geth Storage Contract pragma solidity ^0.5.2 < 0.7.0; contract Storage { uint public val; } Registry Contract pragma solidity ^0.5....
0
votes
0answers
22 views

Why am I getting the error "Expected pragma, import directive or contract/interface/library definition?

I have "pragma solidity ^0.5.9" at the start of the file yet I still get this error. Listing.sol:1:1: ParserError: Expected pragma, import directive or contract/interface/library definition. ...
1
vote
1answer
28 views

How to find the Bytecode of Ethereum Smart Contract by just it's address using JSON RPC

I am wondering that is there any way to find the byte-code of the Smart Contract which is published on a blockchain just by having only idea about it's contract address using JSON RPC running at 8545 ...
0
votes
0answers
13 views

How to use bip39 module in angular?

I am trying to create an ethereum wallet app using Ionic. I have tried to import bip39 node module directly in the angular project but it gives me error. Please help import { Injectable } from '@...
2
votes
2answers
47 views

Is there a maximum/optimum amount of ERC-721 that can be issued per contract?

Take a role playing game as example in which players are allowed to create any number of characters (each one defined by an ERC-721 token). What would be the consequences of having more than 10 ...
2
votes
1answer
22 views

Documenting Smart Contracts and Dapps - community standards and tools

Do you guys know of any kind of documentation standards that are widely used within the Ethereum community? Any kind of documentation tools will also be of great help. Thanks in advance.
2
votes
2answers
101 views

Is my ethereum solidity contract correct and safe

I am very new using Solidity to create Ethereum contracts and would like to know if the contract I have created is first correct and safe to use. What I am doing in this contract is allowing the user ...
4
votes
1answer
24 views

What is the meaning of Ethereum mainnet genesis block extradata value?

Mainnet genesis bloc (see https://etherscan.io/block/0) has 0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa as extraData value. It doesn't seem to convert to ascii and, as this ...
0
votes
1answer
27 views

How to get notification right after account has received eth by geth?

My server stores many accounts. How do i know when and what account has received eth or i have to check them manually one by one by looping many address to check the balance? account := common....
-2
votes
1answer
27 views

Ethereum address not find

Any one tell me how to know about which website generates this ETH address: 0x6fdd1c34b75b8638d3806adecbcbbc61ed4ed3b3
0
votes
0answers
34 views

Issue in truffle unbox zeppelinos/zepkit

As it is visible in the screenshot, I did not get a green check in the "setting up box". Anyone know why it is happening and will it cause any issue in the future?
0
votes
1answer
18 views

In node.js event is not fired

I am using web socket to get event. sending transaction works fine. but event is not fired. also I referred Web3 events not working but it does not work, too. I used eventemitter also. but it did ...
0
votes
1answer
18 views

Does the Wallet Griefing Attack still Exists?

I read about Wallet Griefing attack at the following link: [Ethereum Griefing Wallets][1] 'send' is checked but contract uses throw. The code is given below: for (uint i=0; i<investors.length; i+...
0
votes
1answer
43 views

what does external means ? how can i call the test2() inside my class

pragma solidity ^0.5.7; contract Test { function test() public view returns (uint){ return 10*10; } function test2() external view returns (uint){ ...
1
vote
1answer
19 views

How to test events that were sent by inner transaction / delegate call?

Usually, using truffle I can check for events like this: let { logs } = await myContract.doSomethingImportant( xxx ); // 1500 tokens are expected to get expectEvent.inLogs(logs, '...
1
vote
0answers
22 views

Example of Signedness Bug in Smart Contracts

I found an example of underflow bug at: Catching Vulnerable Smart Contracts Once and for All contract UnderflowAttack { ... function withdraw (uint amount) public { require(balances[msg.sender] -...
2
votes
1answer
22 views

Finding an element in array

pragma solidity ^0.4.17; contract Transport { address public manager; Car[] public carArray; Bike[] public bikeArray; struct Car { uint carId; address carOwner; } ...
1
vote
0answers
18 views

Why after managing to deploy contract to POA Ethereum blockchain I can't interact with it?

We are using a private ETH proof of authority blockchain. In order to deploy a contract I'm using 0 gas price and it deployed immediately. Then, Tried to deploy many types of contracts with ...
2
votes
1answer
29 views

How to pay gas fee for new addresses of ERC20 tokens that initially have 0 Eth balance?

I have a confusion, When we create new address/account for an ERC20 token then it have 0 Eth balance. When we send some tokens to this address and then withdraw token again from this address require a ...
1
vote
0answers
29 views

Trying and failing to switch my dapp from local node to infura, please help? [on hold]

I have a nodejs 'server' running that listens for events on the blockchain. Currently I have this line in my code: var provider = new Web3.providers.HttpProvider("http://localhost:8545"); But I'm ...
1
vote
1answer
19 views

Is it possible to connect to public Ethereum like blockchain with Remix to deploy and view contracts?

I've tried to do so by specifying the web3 provider and the 8584 port but it gets stuck on every try. Is this possible? if so, is there another solution for that need?
1
vote
1answer
16 views

Issue Deploying Contract LinkedIn Course - Ethereum: Building Blockchain Decentralized Apps (DApps)

I'm completely new to Ethereum Smart Contracts. I'm following the course on LinkedIn [Ethereum: Building Blockchain Decentralized Apps (DApps)]. I've been able to compile the smart contract as per ...
1
vote
0answers
15 views

Private Etherum to work like Main Net

I want my private Ethereum blockchain to work like the Main net, I want to fix the number of mined ether (Set Max Cap over minded ether), and don't want that miners earn by mining empty blocks.
1
vote
1answer
24 views

How do i create account remotely?

I have two servers, one for eth-node, one for web api and user db. I want to send request to create account from web server to eth server, but i see it can be created by running command like geth ...
1
vote
1answer
37 views

Solidity Error Address / Address Payable

I'm currently learning solidity programming to create a basic smart contract based on a 2018 tutorial where solidity was using version 4. I'm currently using truffle v5.0.21. I understand that there ...
1
vote
1answer
27 views

web3 - Contract deployment has been reverted by the EVM

I want to deploy a contract but my transaction gets reverted. This only happens with Web3, while it works fine with Remix.I can assure the ABI and Bytecode are correct because I pasted them from Remix,...
1
vote
1answer
34 views

web3 unlock account error

I have two geth nodes, each has an account: node1(IP:192.168.43.12): account1 node2(IP:192.168.43.39): account2 the two accounts are created using geth --datadir /root/chain/node1/data account new, ...
1
vote
1answer
21 views

Newbie. Getting cannot read property 'abi' of undefined when trying to deploy on Ubuntu

let abi = compiled.contracts.example.PartyTime.abi; This is the line of code that is causing the error. I copied the abi code from Remix into an abi.json file. But it doesn't seem to be reading it ...
1
vote
0answers
18 views

How to create ethereum wallet with multiple node? [on hold]

How to to create ethereum wallet with multiple peers for single node? Need to create private ethereum network with 1 node & it's 2 peers. Each node should have 2 accounts.
1
vote
0answers
7 views

Nodes from private network don't gossip

I have three Ethereum nodes created with Geth. Two of them are on my machine (MacOS) and the third one is running on a virtual machine with Ubuntu. Because I used the same genesis.json and also the ...
1
vote
1answer
28 views

Smart Contract is being deployed but call does not return contract address after deployment

So I have been trying to deploy a smart contract using nodejs, but when I call the function to deploy, I get no contract address on my console. It's like the send() function never completed its ...
2
votes
0answers
31 views

How the following pairing equality be verified in Etherum Smart contracts?

I have found available precompiled contracts in solidity. For example, this answer enter link description here points out a precompiled contract that can verify BLS signature. However, looking to the ...
1
vote
1answer
14 views

Detection of var vulnerability: problem with search string

SmartCheck tool at: SmartChek: Static Analysis of Ethereum Smart Contracts suggests detection of 'var' key word in the smart contract by searching the assignment statement such that the Left Hand Side ...
1
vote
1answer
10 views

Was testing this code I found online but keep getting errors?

pragma solidity ^0.5.0; contract Courses { struct Instructor { uint age; string fName; string lName; } mapping (address => Instructor) instructors; address[] public instructorAccts; ...
0
votes
0answers
21 views

Drizzle Installation: pauses at fetchMetadata: sill resolveWithNewModule http-https@1.0

I am following this tutorial https://www.trufflesuite.com/tutorials/getting-started-with-drizzle-and-react. Everything is working smoothly until I have to npm install drizzle. I then run into the ...
2
votes
2answers
16 views

What is the latest implementation of approveAndCall() - Solidity ˆ0.5.0

Just curious for some background on approveAndCall() 1) Is it initially an ERC223 method ? or is it officially part of the ERC20 interface ? 2) Also Im working with an old contract so Im wondering ...
1
vote
1answer
15 views

Error in Declaring a Sized Array: Generating no gas Exception

I have created a fixed size array: pragma solidity ^0.5.1; contract Underflow1 { uint8 arr[256]; uint8 i= 0; function testf2() public returns (uint8){ for(i=0; i<arr.length; ++i);...
1
vote
1answer
18 views

I've given Gwei less than 0.1 for a transaction, and it's been an hour, and it is not showing up in etherscan!

I know I pretty much messed up with Gwei, I've given it < 0.1. My doubt is if the transaction gets failed will the funds get back to my wallet or lost forever and how much time will it take for the ...
1
vote
1answer
16 views

Private Blockchain

Suppose I create my own private blockchain using Ethereum over the public network means my node is reachable from the internet, now I don't want to share my genesis.json but still want that other can ...
1
vote
0answers
26 views

Using web3j with infura returns null

I've used web3.js to handle my contracts, and it worked very well. But web3j is pretty hard for me since the beginning. I'm using android studio, infura, web3j. Since I don't know very much about ...
1
vote
1answer
37 views

After EIP 198 introduction, how much gas is required for RSA signature verification in solidity?

Thanks to the introduction of EIP 198, RSA signature verification is now feasible in Ethereum. How much gas is required for such a verification?
3
votes
1answer
21 views

Compilation error using SafeMath

I am trying to do subtraction operation using the SafeMath library. The following is my code: pragma solidity ^0.5.1; library SafeMath { function sub(uint256 a, uint256 b) internal pure returns (...
1
vote
1answer
20 views

Infura event listening [duplicate]

I am using Infura, Ropsten Test network, Web3@0.20 in the back-end of my Express website. I want to listen events in my ERC20 contract. I tried a lot of methods, but still failed. How do I revise it? ...
4
votes
1answer
25 views

Timestamp in Ethereum

I have a smart contract where the user inputs temperature readings, I'd like to add a time stamp to relate those reading with a current time of submission. I understand that in Ethereum we only have ...
1
vote
2answers
42 views

Storage/Retrieval of mapped structure data

I want to store the structure data in a mapping i.e. if I have a student structure as described below, then I should be able to have a myriad of students and distinguish between them using wallet ...
1
vote
0answers
8 views

Problem connecting web3 via websocket to node with nginx

we are trying to connect to a geth node via WebSockets to be able to subscribe to contract events. This node is created with docker and this docker uses nginx as a proxy. We can connect easily with ...
0
votes
1answer
13 views

Why do my events not emit the correct value?

When testing a contract with Truffle, I have found that the variables that are emitted by the event do not match the values that are passed into the event emission. Why does the event not return the ...

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