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Questions tagged [blockchain]

The Ethereum blockchain is a distributed database based on the Ethereum whitepaper specification and stores both the full transaction list and the most recent state.

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I'm getting an error while deploying project [on hold]

the error saying that could not find required file index.html in the location what it shows, but the file index.html is available in that location which it shows
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1answer
12 views

I am trying to build a land registry of land titles on the blockchain,

Good Day. I am trying to build a land registry of land titles on the blockchain, with the intention of being able to sell such title to someone else. Therefore, the title eventually has to be ...
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12 views

Smart contract migration through Proxy delegate pattern in solidity 0.5

I am trying to do smart contract migration in solidity 0.5 using the proxy delegate pattern. When I write the integration test in javascript how should i make a delegate call using the proxy contract ...
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1answer
13 views

How to get parameters of an object from array using loop

I am using a loop to retrieve an object from array. Then get its details and compare it with other string. But it gives error Type bytes32 is not implicitly convertible to expected type struct ...
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2answers
32 views

Encryption and Decryption when transmitting data

If I was sending data to a smart contract, do I need to encrypt it before transmitting and decrypt it in the smart contract? Or is this done automatically?
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16 views

Deployment of smart contract

How to deploy a smart contract on my own blokchain network? I have created using python and running on postman client server interface. I have already tested on ganache , solidity IDE and ethfiddle.
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1answer
17 views

Blockchain Hark Fork System Impact - risk assessment and mitigation plan

I am exploring on System Impact risk assessment and mitigation plan during a block chain (ex –Ethereum) hard fork. 1) What happens to the deployed smart contracts when a hard fork occurs? 2) Does ...
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1answer
24 views

Can I avoid manually changing code from solidity 0.4.17 to 0.5?

I'm totally newbie in blockchain programming and I have a situation: I have to continue the project written on truffle framework with solidity version 0.4.17, the problem is that I couldn't manage to ...
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1answer
22 views

should I use server side rendering(Next.js) for a dapp?

Recently I have been studying a lot about dapps and now working on a little complex one. So what I wanted to ask is which is better for a dapp ? SSR or CSR ? I have read in a couple of places that we ...
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2answers
48 views

Can we do ethereum transaction for free on private blockchain

I am very new to ethereum Blockchain. Please give some suggestion regarding one query regarding gas fee. Can we do ethereum transaction and smart contract deployment for free on private blockchain ...
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1answer
28 views

Blockchain usage in smart home

I am currently gathering information for my thesis about smart home implementaton with a use of blockchain. The blockchain usage is a requirement from my thesis supervisor and I have huge problem with ...
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0answers
17 views

Couldn't open browser

preetam@LAPTOP-84LFN4UL:~/kyc-ethereum-dapp$ npm run dev pet-shop@1.0.0 dev /home/preetam/kyc-ethereum-dapp lite-server ** browser-sync config ** { injectChanges: false, files: [ './**/*.{html,...
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49 views

How can I store every credit or debit card payment transaction on an Ethereum blockchain? [closed]

pragma solidity 0.4.25; /** * @title SafeMath * @dev Math operations with safety checks that throw on error */ library SafeMath { /** * @dev Multiplies two numbers, throws on overflow. */ ...
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19 views

ERC721, approveForAll-implementation, and others

I am currently implementing ERC721 as the standard for token-exchange in the game I am programming. I am taking inspiration from the CryptoKitties-smart contract. One thing I have realized, is that ...
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0answers
16 views

Flask - Smart Contract Example [closed]

I am new to blockchain technology and I am looking for a smart contract implementation example using flask. Any leads will be much appreciated.
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1answer
17 views

Cannot read property 'hexToAscii' of undefined

deployedContract.deploy({ data: bytecode, arguments: [listOfCandidates.map(name => web3.utils.hexToAscii(Rama))] }).send({ from: '0xfb9286cde20bbd5ed60ee3bb156f9d9938c5b151', gas: 1500000, ...
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1answer
17 views

how to connect my html form that is username and password to blockchin and taking the username as metamask key?

I am developing a decentralized cloud web application, when the user will login into the application he/she will generate password from blockchain, I am not getting how to connect my html form that is ...
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1answer
29 views

Ideal way to store hash on the ethereum blockchain

I would like to store a certificate on the blockchain. I only need to store its hash and if its been verified by both parties or not. Should I create a struct that is made up of bytes32 for the hash, ...
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0answers
17 views

Error while running npm run

sh: 1: lite-server: not found npm ERR! file sh npm ERR! code ELIFECYCLE npm ERR! errno ENOENT npm ERR! syscall spawn npm ERR! eth-todo-list@1.0.0 dev: `lite-server` npm ERR! spawn ENOENT npm ERR! npm ...
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0answers
14 views

BlockChain Suitable for Payment based Mobile App [on hold]

I have a requirement where mobile app with below main specifications needs to be developed: Process user's check deposits and direct deposits and load amount to user's wallet. Peer to Peer Payment (...
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1answer
35 views

web3.eth.getAccounts(console.log) Error

Can you please help me with this error ! How to fix this ?? web3.eth.getAccounts(console.log) TypeError: this.provider.sendAsync is not a function at RequestManager.sendAsync (/home/...
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0answers
63 views

About gas limit and gas

I'm developing Dapp, In that app one function consuming a gas but I am providing sufficient ether at the time of initiating transaction by web3 for the Dapp Users,Then also it is showing out of gas ...
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1answer
22 views

Smart contract to strore and retrieve address and ID in blockchian using mapping

I want to store some address and their ids in blockchain using mapping and i want to know how to get the stored addresses when searching with their respective IDs.
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1answer
42 views

Doubt in terminologies used in Ganache Interface

I am developing a DApp (an e-commerce app) based on Ethereum. I wrote the solidity contract and interact it with a NodeJS server/web3js API. I am running a Ganache Ethereum RPC client locally. The app ...
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0answers
12 views

ethereum smart cotract ioT implementation

For the preparation of a project in my thesis, I need to implement ethereum blockchain to control the access of the IoT using smart contract. Can you recommend me a tutorial to prepare this without ...
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1answer
22 views

Can Artificial Intelligence be used to mine ethereum faster? [closed]

Can Artificial Intelligence algorithm be used to improve hit rate of mining ethereum?
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1answer
23 views

Possible replay attack when paying to smart contract

I am afraid of a possible replay attack when paying to a smart contract. Given these 3 assumptions An action gas cost may change according to the state of the blockchain (even if its the same action)....
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1answer
27 views

Solidity Contract Needs Another Contract's Address

Is there a way for a Solidity contract to programmatically find out another solidity Contract's address? Right now I'm letting Contract A know about Contract B by hard-coding the address of B into ...
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1answer
22 views

“ app.candidates is not a function” getting these error while caling the function through truffle console with "app.candidate'

pragma solidity ^0.5.0; contract Election { //Model a Candidate struct Candidate { uint id; string name; uint voteCount; } //Store Candidate //Fetch ...
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1answer
22 views

ERC721 Contract vs. Auction Contract - Architectural Approach [duplicate]

I'm working on a new ERC721 Crypto-Collectible project, which also means creating an Auction and Marketplace functionalities into the whole thing. Should I just start with a basic ERC721 Contract - ...
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0answers
29 views

Query Ethereum Blockchain for functions return value of a Specified Smart Contract

I want to get smart contract functions return value sent by a specified smart contract within a range of blocks. I found a [manual] working method to achieve this: async function getTxsByAccount(...
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1answer
17 views

Solidity modifier with function call error

pragma solidity >=0.4.22 <0.6.0; contract Person { //owner address address private owner; //identity string private firstName; string private lastName; string private ...
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0answers
18 views

Randomised DPOS for Ethereum VM?

Clique (POA) seems to have awesome configuration possibilities to make it work like a DPoS or a randomised DPoS DPoS : Selects a set of masternodes (maybe 18-25?) which have staked native fuel (ETH ...
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1answer
74 views

web3.min.js is missing in ./node_modules/web3/dist

I am following the below tutorial to create implement blockchain using web3. https://medium.com/coinmonks/interacting-with-ethereum-smart-contracts-through-web3-js-e0efad17977 When I am using npm ...
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2answers
44 views

Create a blockchain platform to store students and its degree results on it [closed]

I would like to create a application on blockchain where i will store all students data and their results on blockchain So anyone having a idea how can i do that or is that feasible to create a that ...
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2answers
56 views

Blockchain Smart Contract EHR

I'm trying to do a miny EHR(Electronical Health Record) with Smart Contracts where I have a Pacient Contract. The problem is that in solidity everything is public, even the private variables, so I ...
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1answer
17 views

ParserError: Expected primary expression

Following is my code: pragma solidity >=0.4.17; contract Lottery { address public manager; address[] public players; constructor () public { manager = msg.sender; } ...
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1answer
31 views

How Ethereum blocks are stored?

Is each block on Ethereum blockchain stored as lots of files, a separate file per each block? Or a database? How does one can run Etherenum node shared over several servers?
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1answer
14 views

What is the advantage and disadvantage of deploying Erays on Ethereum?

I have read this paper, Erays: Reverse Engineering Ethereum's Opaque Smart Contracts. They proposed this reverse engineering tool for Ethereum smart contracts. it will take as input a compiled EVM ...
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1answer
35 views

can we pay the gas price in form of token?

can we pay the gas price in form of ERC20 token without using the ether? if ERC20 token has a value.then can we pay the gas price in form of ERC20 token.
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1answer
16 views

Costs in gas of changing the value of a variable

Maybe a little bit weird question, but can the amount of gas, when: SSTORE is used(for changing an existing variable), be lesser than 5000 gas? If no, are there discussions in community to reduce ...
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0answers
39 views

Syncing from hardcoded block in parity light client?

I need to sync my parity light client from a hardcoded block. I synced the light client fully in a Debian image and exported the hardcoded sync. I then pasted it in the chain spec file of a desired ...
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1answer
17 views

How to make transactions real-time for Dapps

I am intrigued how exactly an Ethereum transaction's "state changing" works. I have read about the Bitcoin transactions, and so understand how the basics of validation and propagation through the ...
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0answers
12 views

The granularity of the blockchain transaction and gas

Trying to understand at what granularity the blockchain transactions and gas are recorded. If every modification to the AST is considered a transaction and permanently stored, or if it's something a ...
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1answer
116 views

RPC Error with Payload when using the Ropsten Test Network Faucet with MetaMask

I'm trying to obtain some test ether from the Ropsten Test Network with Metamask, but I keep on getting an "RPC Error with Payload", whenever I try to click on "request 1 ether from faucet". I ...
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1answer
114 views

truffle migrate not working

every time I enter truffle migrate command in the terminal it doesn't does anything but takes some time and nothing happens after that. I am using Truffle version 5.0.4
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1answer
27 views

ParsedContract.sol:1:17: ParserError: Token incompatible with Solidity parser as part of pragma directive

Code : git clone https://github.com/dappuniversity/election https://github.com/dappuniversity/election/tree/2019_update Errors faced : Commands: Compile: truffle compile Migrate: ...
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2answers
28 views

What are differences between bitcoin and etherum trancactions?

I have read about how transactions work and how they can be redeemed in bitcoin. In a very abstract way, the sender defines the output script that should redeem the transaction. But I am new to ...
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2answers
34 views

Blochchain Smart Contract App

Actually Im working on a blockchain application based on smart contracts that allows to buy/sell properties and paying in cryptocurrency using Ethereum and Bitcoin. I wonder I develop smart contract ...