All Questions

-1
votes
0answers
22 views

How to create a security token in ethereum ropsten testnetwok

I want to create a security token like ST-20 in ethereum. where i could start.Any suggestion
2
votes
2answers
103 views

Verifying Modular exponentiation operation in etherum

I have Alice who should do some cryptographic operations off-chain. Then a smart contact has to verify equality by performing Modular exponentiation operation. I attached an image of the off-chain ...
0
votes
0answers
13 views

Genesis.json Change Name from ETH to Any other [duplicate]

I want to change the name of the currency while setting up my private ethereum node, is it possible ? and if possible how can we change it ?
0
votes
2answers
26 views

how to write backend for contract if you use infura ropsten metamask and remix

i'm using metamask with ropsten. deployed my contract on ropsten using remix. for the backend i used infura to create instance of web3. ew Web3(new Web3.providers.HttpProvider('https://ropsten.infura....
1
vote
1answer
30 views

ERC721: Interface ID Registration

Why we need to register Interface ID in ERC721 token. I was just going through the openzeppelin-solidity erc721 code and curious to know that why we need to use this. That interface id register code ...
3
votes
1answer
58 views

Is there a “Hello world” smart contract in ewasm?

Is there any ewasm smart contract for testing? The example contracts of parity cannot be deployed due to exceeding block gas https://github.com/paritytech/pwasm-tutorial/
0
votes
1answer
26 views

How can I wait if it's not possible in smart contracts? [duplicate]

From my understanding, waiting in a solidity smart contract would create a total disaster for the whole Ethereum's blockchain. I can see in some circumstances that solidity offers block.timestamp ...
0
votes
1answer
35 views

How to use eth_newFilter to get pending incoming transactions to a contract?

I'm trying to get pending transactions to a certain contract using Infura. Is it possible to do that using eth_newFilter? Since apparently these filters only "trigger" from contract events, does that ...
0
votes
1answer
20 views

How to calculate average gas price of several blocks?

I want to calculate average gas price of several blocks (in Gwei), however I don't see how a field on blocks for gasPrice. Do I have to calculate it by grabbing the gasPrice of each transaction in ...
1
vote
1answer
41 views

truffle deploy live | transaction not mined within 750 seconds

I'm trying to deploy my smart contract to the live ETH network. I've done the same process on rinkeby and it works fine. However during the block mining phase it times out and gives the error: " ...
2
votes
1answer
47 views

Couldn't connect to node because cross-origin request is blocked

I am running a full rinkeby node via geth --rinkeby --rpc --rpcapi db,eth,net,web3,personal --cache=2048 --unlock="..." --password ... --rpccorsdomain "*" --allow-insecure-unlock --rpcaddr "...
0
votes
1answer
26 views

Updating ERC20 Contract from 0.4.0 to 0.6.0

Im updating some ERC20 contact code from solidity 0.4.0 to 0.6.0 and hitting some snags as it seems openzeppeling has changed its structure since then as can be expected. I cant access the balances ...
0
votes
1answer
26 views

Remix - Pass bytesX to function

Using Remix, I can't pass a set of bytes ["0xee", "0xff", "0xgg", "0xhh", "0xii"] to my function function foo(bytes5 input) { // Do something } I've already tried all these formats: ["0xee", "...
0
votes
1answer
25 views

How to swap tokens?

Say I have a X token and Y token and I want to swap X tokens in exchange for Y tokens. How can i do that? Its like during crowdsale, instead of using ether to buy the Y token I want to accomplish the ...
1
vote
0answers
22 views

Extra mining fees added in etherbase account

1st scenario - I have set miner.setEtherbase(eth.accounts[1]) and gasPrize is 0. 1 coin Transaction - And done transaction from 0th account to one random account. I expect 0 mining fees will add ...
0
votes
1answer
25 views

Web3 Contract.balanceOf is not a function

I have read this helpful SO answer about sending ERC20 contracts, but it seems that the Web3 docs and API have changed dramatically since then. I am trying to get the balance of a smart contract using ...
0
votes
1answer
15 views

Web3: How to get price of ETH at time of transaction?

Example transaction: https://etherscan.io/tx/0x2edfb0bf11355a48bbb93c567a8c6de39f80de515ceb8b26dbcbf4729bd8a217 In code given a transaction object, how would I fetch the price of ETH at the time of ...
0
votes
1answer
19 views

Create custom mobile wallet for my two ERC20 Tokens

I have two ERC20 tokens that I created on Ethereum. I would like to know if it is possible for me to create a mobile application that will allow my users to check their balance (for tokens) and ...
1
vote
1answer
27 views

Lib to sign messages using the same version of ECDSA of Ethereum

I want to sign a message using the private key of my physical RSA digital certificate and I want to validate this signature onchain. Does anyone know a lib that can sign messages offchain using the ...
0
votes
0answers
13 views

How to get web3.eth.getPendingTransactions on JavaScript?

I read in the official document for web3js v1 https://web3js.readthedocs.io/en/1.0/web3-eth.html#getpendingtransactions getPendingTransactions web3.eth.getPendingTransactions([, callback]) ...
0
votes
1answer
38 views

how to securely share digital asset in a fully decentralized DApp

I want to design a proof of concept of a fully decentralized secure asset sharing DApp. Seller uploads the asset they want to share with a price and buyer pays it with ether or a token. Frontend and ...
1
vote
0answers
23 views

How to access Parity node's mempool with web3.py?

I'm running a Parity node with parity --jsonrpc-api all, then connecting to it in python3 with w3 = web3.Web3(web3.HTTPProvider('http://localhost:8545')). I can call print(w3.eth.getBlock('latest'))...
0
votes
1answer
26 views

Are there any smart contract templates?

I'm looking for one or more possibly open source Ethereum smart contracts that have been tested and perform some useful use case.
0
votes
1answer
18 views

Can't import a contract interface in vyper

I need to import a contract interface using the JSON ABI but I get syntax error when trying to import the interface. I have created the JSON file in remix and named it IERC1620.json then I am trying ...
0
votes
2answers
46 views

Solidity: “send” and “transfer” are only available for objects of type “address payable”, not “address” [duplicate]

I'm trying to compile my smart contract with the solidity version 0.5.0. with the code below: function unbond(address wallet, bytes32 specifier, uint quantity) internal { bondage = ...
0
votes
1answer
40 views

mishandled exception: can't understand research paper content

What is the meaning of following paragraph in the context of ISZERO & mishandled exception. I found an article at: enter link description here It says that: Detecting a mishandled exception is ...
0
votes
1answer
56 views

Solidity: Convert from “bytes memory” to “address”

I'm using solidity 0.5.0 and when i try to compile my contract it's giving me this error Explicit type conversion not allowed from "bytes memory" to "address" my code is this: /// @dev get broker ...
0
votes
1answer
14 views

How to create account by web3 0.20 version?

I try to create new account by using web3, i found that I can only do this in 1.0 of web3 but not in 0.20 version? it does not support personal.newAccount
2
votes
2answers
31 views

Web3.js - where to find prepackaged bundle to be included with my HTML page

Is there any way i can download web3.min.js and include "" in my html directly, without using npm to install, just like adding a js file, i know there is 0.20 version but i cannot find the version of ...
0
votes
0answers
30 views

React + Ethereum + Solidity. Private Blockchain ether mining issue?

I'm making an app using react, ethereum and solidity. I'm signing up the user using.. web3.eth.personal.newAccount(); Then all users need to do certain tasks on app. They need to do certain ...
0
votes
1answer
33 views

Block signer address question

I set up a private clique POA chain with 3 nodes, all of them are sealers. I launch two nodes only, the blocks can be signed by the two nodes. when I call clique.getSignersAtHash('block hash value'),...
0
votes
1answer
18 views

Smart contracts: is every public function payable?

I am aware of the payable annotation on the public methods. But just want to make things more clear: is every public function payable? Even without the payable annotation? what would happen if a ...
0
votes
1answer
42 views

geth never completes syncing for rinkeby

My aim is to synchronise a full node for the Rinkeby network. It seems that geth does not finish synchronisation. I have had it run for over three days, but it is stuck at the last few blocks. > ...
0
votes
1answer
20 views

Load another deployed contract's public values

pragma solidity ^0.4.24; I'm trying to call another contract's functions to return values. I have the below which successfully returns a true/false _childAddress.call(bytes4(keccak256("...
0
votes
1answer
61 views

miner.start() is not a function?

"web3": "^1.0.0-beta.37" "web3": "^1.0.0-beta.55" import {Miner} from 'web3-eth-miner'; then const options = { defaultAccount: "0x78dB3e2129D58685444989dD9682DDDC70dd3C82", ...
1
vote
0answers
68 views

Transaction exited with an error (status 0) after consuming all gas

I developed some smart contracts to be deployed to a private PoA (Proof of Authority) blockchain. I spun up a private blockchain via truffle develop and got the following receipt: Compiling your ...
0
votes
0answers
30 views

Test Events using Truffle and Ganache

I am testing the following contract (removed non relevant parts for brevity) pragma solidity ^0.5.0; contract GameManager { address[] public deployedGames; address public lastGame; ...
1
vote
1answer
23 views

Update Private Ethereum node

Now suppose I created my private blockchain using ethereum over any cloud, created dapps over it and created my own crypto over that. Now if ethereum update consensus to POS from POW I want my private ...
1
vote
1answer
47 views

How to create a variable in storage via the solidity assembler

Similar to this question How to get access to the storage array through the solidity assembler? But instead of accessing a storage variable, I want to create a new storage variable via assembly. That ...
1
vote
0answers
49 views

web3.eth.sendSignedTransaction from address is different from Signer's address

I'm signing transactions using an HSM and when using Web3js to send the signed transaction, the from property on the receipt shows an address that's: Different every time a sent signed transactions ...
1
vote
0answers
27 views

Error: Connection error: Connection is not open on send()

After a few hours the socket to Infura seems to drop and we get the error, Error: Connection error: Connection is not open on send() Why does this happen or what is the best way to solve it? version: ...
0
votes
2answers
28 views

How to dynamically generate a variable without declaring it in a contract (solidity)

Is it possible to generate a non-local variable with a function? Weird question but it's for an exercise my senior asked me to do, I've scoured the web for an answer to no avail. Instead of ...
0
votes
0answers
16 views

What's the block header's difference between POW and POA chain?

I want to simulate the processing procedure, from block generation to header verification, on private POA chain, and look into the variables during process. What nodejs modules can be used(not ...
0
votes
0answers
12 views

How to get list of pending transactions for particular address on JavaScript using public API?

I'm building web-wallet on javascript, and I want to show not only available balance, but also pending amount. From web3js v1.xx documentation I've learned that I can do web3.eth.subscribe('...
1
vote
0answers
12 views

Could the parity-ethereum client incorporate doing range proofs in the ethereum blockchain?

I want to be able to prove that I have stored a number that is in the range of a minimum and maximum value, (a range proof) without revealing the number, and put the value into the ethereum blockchain,...
0
votes
0answers
23 views

Expressjs backend (truffle box) with metamask

I use truffle to unbox the express-js box (https://truffleframework.com/boxes/express-box). The code loads the web3 instance in server side which connects directly to ganache. Now I want to be able to ...
1
vote
1answer
22 views

Why does a mapping update itself when I am not doing anything?

The title is a little bit vague but I've seen this contract and tried it on remix: pragma solidity ^0.4.24; contract Tester { struct Account { uint256 balance; } mapping (address => ...
0
votes
1answer
27 views

How many nodes do I need in a Quorum Private Blockchain?

I want to deploy a private blockchain using Quorum on Azure, create some ERC721 Tokens and send them various accounts inside the Private Blockchain. How many nodes do I need for a Private Blockchain ...
0
votes
0answers
7 views

How often should the Web3.py provider connection be shared in a django project?

My django project directory structure is the following ... projectRoot projectName __init__.py settings.py urls.py wsgi.py App1 __init__.py admin.py models.py ...
0
votes
1answer
23 views

which port I use when I want to connect remix to my local quorum network?

I want to deploy a smart contract on my local network. I executed a local node via PRIVATE_CONFIG=ignore nohup geth --datadir ./Node1/new- node-1 --nodiscover --verbosity 5 --networkid ...

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