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Questions tagged [ethereum]

Ethereum is a blockchain currency (like Bitcoin) with a public ledger. Questions should relate to programming. General questions about Ethereum should be asked on https://ethereum.stackexchange.com

is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality. It provides a decentralized Turing-complete virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes. Ethereum also provides a cryptocurrency token called , which can be transferred between accounts and used to compensate participant nodes for computations performed. Gas, an internal transaction pricing mechanism, is used to mitigate spam and allocate resources on the network.

was proposed in late 2013 by Vitalik Buterin, a cryptocurrency researcher and programmer.

The official website of is Ethereum.org

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web3js call fails on missing contract address

To deploy a contract on my local set up I use truffle. The development network is running by Ganache. Also sending data on to the network from app A is no problem (using truffle/truffle-contract packages). I start this app in the same working…
Crittje
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ERC721 implementtations

I am trying to create a smart contract for renting things [any items ] I want the items to be an ERC 721 token . From what I read ,to implement ERC 721 tokens I need implement the ERC721 class from the open zepplin library. So the token contract…
Tanmay Bhattacharya
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Add Peers does not add a peer in Geth console

I am trying to add a peer. I created two nodes using the following commands on geth.The boot node creation command is geth --datadir ./chaindata3 --port 30304 --nodiscover --networkid 12 --rpc --rpcport "8546" --rpccorsdomain "*" --ipcdisable…
cbhangale
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How to integrate uPort mobile app with my app?

In uPort documentation [https://www.uport.me/#resources] there are steps to integrate uPort with a webapp, but can anybody share an example of how to integrate uport authentication for android based DApp ?
NaN
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Ethereum: How to deploy slightly bigger smart contracts?

How can I deploy large smart contracts? I tried it on Kovan and Ropsten and have issues with both. I have 250 lines of code + all the ERCBasic and Standard files imported. The size of the compiled bin file is 23kB. Did anybody experience similar…
sunwarr10r
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Is Ethereum suitable for permissioned blockchain?

Got a blockchain related project to impl. Part of the project need permission control, means: Only qualified users (e.g login) could use it. The transaction history is not public, a transaction is only visible to related user or admin user. It…
Eric
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How do I recover ECDSA public key correctly from hashed message and signature in R || S || V format?

I have used the following code to generate an ecdsa key-pair(privKey and pubKey), encode them and then decode them back: https://stackoverflow.com/a/41315404/1901320. Next I create a hash for a message (txnData.Payload() is of type []byte) using…
Samikshan Bairagya
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Implement exponential decay function in Solidity

I am working on an ERC-721 token in which there is a built-in royalty feature, i.e., when a user issues a token, he chooses the royalty fee in ETH and he is entitled to that fee on every secondary market trade. Also, the more tokens a user holds…
Abdul Sami
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How to determine correct contract compilation options?

I've successfully deployed my contract to Kaleido but I'm having trouble figuring out how to correctly verify it. Here is the source code deploys the contract and I've verified the the address printed by the last print statement appears in my…
Paymahn Moghadasian
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Way in solidity to match users address with address defined in array

I am looking for an efficient way to check if the the person invoking a function is allowed to access a function defined in a smart contract by comparing msg.sender with array of addresses that I am hardcoding at the time of deployment in solidity.…
Kushal Tripathi
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The contract code couldn't be stored, please check your gas limit : Ethereum Smart Contract Deployment Failed:

I'm learning how Ethereum smartcontracts are developed and deployed using Solidity, Web3.js, and JavaScript. I've successfully deployed a contract on Ganache. Now when I'm trying to deployed it on Rinkby Test Net using `truffle-hdwallet-provider. It…
Sundeep
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Can the same public address used for Ether be used to receive other coins as well?

I am planning for a cryptocurrency app, and am trying to figure out something I haven't been able to find an answer to. On the Etherum blockchain, a user has a public address used for receiving coins, and a private key used to send. There are also…
Lars Andren
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Smart contracts fallback as a catch all delegatecall

I am practicing some vulnerabilities in smart contracts for my lecture in the university. The contracts that I am practicing on are; contract Company is CompanyInterface { address public ceo; ... function setCeo(address newCeo){ …
riyoz
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Why does my Ethereum transaction cost 21000 more gas than I expect?

Somehow I am getting insanely high gas costs compared to what I think I should be seeing. I have a function in solidity: function setMessage(uint8[] _fMessage) public returns (uint256){ emit Message(_fMessage); } And my event: event…
Cal W
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In truffle test using js, how to set the parameters after the `contract `?

Such as WhitelistedCrowdsale.test.js in openzeppelin-solidity: contract('WhitelistedCrowdsale', function ([_, wallet, authorized, unauthorized, anotherAuthorized]) { ... } in line 12. why the parametes of function(...) is _, wallet, authorized,…
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