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Questions tagged [tokens]

A token is a transferable, divisible object on the blockchain, such as a subcurrency or a prediction market share.

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How do you expose the ethereum private key from the brave browser?

I have some funds on the brave browser, but how do I extract the ethereum private key from the brave browser?
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Ethereum-based project analysis [on hold]

I should make a quantitative analysis on some ethereum-based healthcare project (as MedicalChain,for example) and I need some tools to analyze ethereum network contents. Honestly, I don't know where ...
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1answer
22 views

I want to remove the timed aspect of this crowdsale contract and make it finalizable manually [on hold]

Which lines do I remove and what do I replace them with to change this from a timed crowdsale contract into one I can end manually? pragma solidity ^0.4.18; interface token { function transfer(...
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1answer
27 views

How to fix “No events were emitted”

I have been following the instructions in the Dapp university tutorial. But I am using Windows 10, Dapp University is Mac. I downloaded this truffle with smart contract ERC20 from Dapp university. ...
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1answer
8 views

Add Custom Data to ERC20 token transfer

I'm in a situation to implement the following scenario, Need to transfer ERC20 standard token(own by my contract) to some another wallet. When recording transaction on Ethereum, need to add custom ...
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16 views

How to create security tokens and how profit is distributed? [on hold]

I was searching around security tokens and after googling sometime I got two bird eye view concepts, one is that they are ERC-20 standard based and should pass the Howey test and on other places I ...
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1answer
19 views

Getting and storing address of erc20 contract after dynamically creating it

I have a function which dynamically creates an ERC20 contract on calling a function in another contract as follows: function createDao(string _tokenName) public payable { tokenNumberIndex = ...
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1answer
10 views

How to View All Properties and Attributes of a Token

I am new to Ethereum and have done the basics like go to Etherscan to view token contracts, but I'm curious to find a way to learn more about a specific token. The one I'm interested in is PumaPay. In ...
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1answer
19 views

Why my tokens aren't visible to the address sent in etherscan?

I've flattened the code and fixed the warning. But the problem with the contract is that the tokens are not visible in the addresses when searched with etherscan but when I try to add through Metamask,...
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How could I set my ERC20 token image to be displayed in MetaMask?

Does Metamask load erc20 token image from etherscan? ref: How to verify token after etherscan, and submit icon If not, how do I set my erc20 token icon image to be displayed in Metamask? thanks.
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2answers
21 views

Why it's showing errors in this contract?

Actually, I wrote the code in multiple files, but since I need to Verify and Publish the code so, I tried to flatten the code. But now it is showing way too many errors. I put the code below with ...
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1answer
21 views

how can I pair my ERC20 token with Ethereum

I am building an exchange and i just want to know how this pairing thing works. How can I pair my ERC20 token with other crypto assets like Ether and BTC?
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“Error: gas required exceeds allowance or always failing transaction” for simple AirDropper contract

I try to use simple AirDrop contract taken from https://github.com/omisego/airdrop/blob/master/contracts/Airdropper.sol - https://gist.github.com/Gim6626/083d556e0a41da5172de0c49ffd64577 . It ...
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1answer
21 views

Freezing ERC20 token for certain amount of time?

Is there any functionality like randomly specifying freezing portion and freezing period .For example, we must transfer 100,000 ERC20 tokens to a users. We transfer 10,000 tokens with no restriction, ...
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1answer
19 views

What are contract Variables and how are they different from normal varables declaration

pragma solidity ^0.4.2; import DappToken; contract DappTokenSale { address admin; DappToken public tokenContract; function DappTokeSale(DappToken _tokenContract) public { ...
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2answers
43 views

What is wrong with this code, deployed but showing error while sending ether?

I have tried to compile this code for crowdsale and also have deployed the contract on Rinkeby Network. But each time I send a transaction, it says Warning! Error Encounter during Contract Execution [...
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3answers
36 views

How to create a smart contract that has token and transfers tokens to whoever sends ether?

I want to create a smart contract which is able to create tokens, priced at some amount of ether, example uint price = 1 ether;. Now after someone sends any amount of ether, the same amount of tokens ...
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0answers
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How to build an incentivization model for a behavioural change using smart contracts? [closed]

I have been researching various incentivization models and reading whitepapers regarding crypto-economics(e.g: steemit whitepaper) for a while but is it necessary to have a private blockchain for that ...
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2answers
21 views

Token transfer not dropped no event on MetaMask

I am using the following contract Fixed Contract Example And using this example to transfer token Transfer token example Everything goes fine, i see no error what so ever except MetaMask doesn't ...
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1answer
23 views

Smart Contract that can transfer ETH to other ETH Wallet (Owner of the Smart Contract)

I actually my partner created a Smart Contract which is able to create a new smart contract and send the proceeds. I'm quite new to Solidity unable to figure out a way to modify the smart contract to ...
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2answers
35 views

MEW says not a valid erc20 token but don't see errors

I created a token prior to this one that is fine. I used the same template, followed the same exact steps to create another token but getting the not valid erc20 error. https://ropsten.etherscan.io/...
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1answer
18 views

Smart contract balances question

I have a few questions regarding ETH and token storage. Is it a good practice to store ETH on smart contract address in case only owner is authorized to withdraw it? When deploing smart contract, do ...
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1answer
30 views

How ERC20 and ERC721 deals with confirmation level

a smart contract store the internal balance per owner. when we transfer tokens from Owner A to Owner B, we update the internal balance sheet. but the internal balance sheet is a most recent snap shot. ...
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1answer
91 views

Two ERC721 tokens that refer to the same metadata

This is a question about the ERC721 interface. I understand that the tokens are non-fungible and guaranteed to be unique to a specific account (owner). One possible way to use ERC721 tokens would be ...
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0answers
19 views

How to store & retrieve data in blockchain(Solidity) using merkle tree approach for tracking?

I'm working on asset tracking sample application. currently i'm tracking asset transfer information using events. I would like to store asset transfer information in blockchain using merkle tree ...
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0answers
34 views

ICO for a startup I am planning to build but have some questions [closed]

I am an software developer with over 11 years of experience in industry and has worked as a software developer for some of the leading firms in vacation rental space. I recently started playing around ...
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1answer
21 views

Quick question: can a function send multiple tokens?

And by the question I mean if I can send a couple of few different ERC20's or let's say even 1 ERC20 + some amount of ether in one function?
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1answer
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How to optimize ETH donations in an ICO when receiving ETH from an exchange? (Best user experience)

I'd like to make raising funds in ETH as easy as possible. This is the flow that I'm imagining for my average user: 1) User visits my ICO page 2) They download a key and address file generated in-...
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0answers
34 views

Is there a tool to lookup ERC20 token type via an address?

I'm currently coding on the 0x platform and need to determine the type of token (for example WETH or ZIL) from the token's address. Is there a utility out there that allows me to do this easily?
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How can I remove the remaining burned token?

I've burned the above token. After burning, originally only one holder is right. But there are two holders as above picture. How can I remove the one holder(400%)? This is contract address: https://...
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1answer
24 views

How would I figure out if ethereum or token is being transferred seeing the transaction details?

web3.eth.getTransaction('0x9fc76417374aa880d4449a1f7f31ec597f00b1f6f3dd2d66f4c9c6c445836d8b§234') .then(console.log); > { "hash": "...
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1answer
51 views

How to handle both string and bytes32 method returns?

I have the following code to extract ERC20 token symbols from addresses: const AllTokenSymbols = await Promise.all( allTokens.map(tokenAddress => { const tokenContract = new web3.eth....
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1answer
49 views

CappedCrowdsale of mintable ERC721

I am thinking of building a capped crowd sale using CappedCrowdsale and MintableERC721 of OpenZeppelin. I wonder if its better to mint the tokens once the cap is reached or to mint seperately once a ...
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1answer
42 views

ERC20 transferFrom function results in “Error: gas required exceeds allowance or always failing transaction ”

I'm trying to learn my way around ERC20 tokens and upon attempting to create a lottery contract for an erc20 token the transferFrom function always spawns an error, specifically "Error: gas required ...
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3answers
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ERC-20 transferFrom implementation potential flaw…or not?

Let's say transferFrom function is implemented in a next manner: function transferFrom (address _from, address _to, uint256 _value) public returns (bool success) { uint256 spenderAllowance = ...
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1answer
42 views

Is it a good practice to create a new ERC721 NFT as needed?

I'm prototyping an asset management system using private blockchain and one of the main event is adding a new asset to the system. I was thinking about creating a new token when the asset is added to ...
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1answer
28 views

Can someone imitate and create a fake erc20 contract? If so, how can we identify a contract?

If a project A deployed a erc20 token contract Mytoken, can a scammer create another Mytoken with some internal data modified (e.g., founder address)? Can etherscan identify such fake contracts? Or ...
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0answers
48 views

0 ETH Airdrop function with ICO contract

I see many airdrops that have been done by sending 0 ETH to the ICO contract address my question is: how to add this function to the ICO contract with the ability to start and stop at any time? and ...
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1answer
37 views

How do exchanges transfer tokens from user wallets?

​ I am wondering how exchanged like Binance are able to transfer out tokens from user wallets that have no ETH in them? ​ For example if I create a new binance account and say I transfer ADA from ...
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1answer
25 views

Where are tokens stored from an implementation level

I have the following questions: 1.From a LevelDB perspective, where are tokens stored? Is it part of account info? Or is it only part of the smart contract? If it is only part of the contract, how ...
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1answer
54 views

Clarification about Dogethereum

Can someone explain me the Dogethereum project? I mean, is it a token managed by a smart contract (through a bridge) or is it a full independent blockchain whose code is based on that of Ethereum, ...
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0answers
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What happens to the missing coins in this transaction? Copy paste this code into remix to reproduce my original bug. Thank you

pragma solidity ^0.4.24; contract TheCaseOfTHeMissingCoins{ string public name; string public symbol; uint8 public decimals = 18; address public owner; mapping (address => ...
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2answers
62 views

Create and Run an AllowanceCrowdSale With Zeppelin-OS Contracts

I use the openzeppelin library: https://github.com/OpenZeppelin/openzeppelin-solidity/tree/v1.12.0 token I create a BurnableToken: pragma solidity 0.4.24; import 'openzeppelin-solidity/contracts/...
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0answers
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How would ICO smart contracts function under these scenarios?

Having been inspired by an idealistic desire to attempt a way forward amidst ongoing diplomatic crises, I hired a team to help me create a mega-infrastructure ICO project at Beringia.io - but I ...
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1answer
28 views

How to charge all gas fee to a General Master Wallet

We are currently developing a blockchain platform that deals with sending of tokens from users to users, and as you know, ETH is required as a gas fee to be paid for any ERC20 token transfer from a ...
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1answer
12 views

How to add multi sign master wallet to a smart contract [closed]

How can I add a Multi Sign Master wallet features to a Smart Contract
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1answer
26 views

Are there ways to optimize Approve and Transfer?

Let's take the following use case: I want to allow a smart contract to transfer some erc20 token (from another contract) for me. So what i assume i should do is: Create and publish an approve ...
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1answer
52 views

Why use returns(bool) in a transfer function?

function transfer(address _to, uint256 _value) public returns (bool) { require(balanceOf[msg.sender] >= _value); require(balanceOf[_to] + _value >= balanceOf[_to]); ...
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1answer
32 views

OpenZeppelin MintableToken error only on private network

I started a new private network by geth command. geth --networkid "198" --nodiscover --datadir "~/test-geth" --rpc --rpcaddr "0.0.0.0" --rpcport "8545" --rpccorsdomain "*" --rpcvhosts "*" --rpcapi ...
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2answers
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HI, can i get live Ether to USD price in my smart Contract ? I want to keep a hardcap in USD. is it possible to do so?

I want to make a function for my ICO to calculate ethers collected so far and convert them into USDollars. I wanted to hard cap my ICO in USDollars. Is it possible to do so ? I am using Solidity to ...