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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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3 views

I'm getting an error while deploying project

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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2answers
43 views

Ethereum Enterprise Blockchain

I am starting a project that I need to build a solution to track products (ex: from farm until it gets to the supermarket) Basically, I need to set up a blockchain structure for my company(private) ...
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1answer
11 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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1answer
399 views

How reliable is it to use Block number to calculate Time in Smart contract?

I have seen contracts use block numbers to manage when the crowdsale should start and stop. How reliable is this? I understand the average time in ethereum is 17secs between blocks, but can this be ...
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2answers
170 views

Is it possible to create a tool that reads smart contracts and check if it's safe?

I'm really in need of help with my thesis project. I'm currently finding the gap that my adviser is asking for and I seem to be having a hard time with it. What I could think of is actually creating a ...
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0answers
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
227 views

IPFS. Add a directory recursively with an HTTP api

Is there an HTTP api equivalent of doing: ipfs add -r resources/public where resources/public is a directory with a static website (index.html in the root, css, js etc). Doing: curl -F file=...
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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
35 views

How can you tell if a mined transaction made permanent changes?

I have set up a private ethereum blockchain and I have defined a new coin. When I send coins from one account to another through the smart contract the transaction is always mined even when the coins ...
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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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7answers
113k views

What are the Ethereum disk space needs?

How fast is Ethereum blockchain growing and how big is it likely to get in the future? Is it still about 1 GB per month? Are there any data pruning or compression algorithms in place?
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1answer
41 views

Restricting payment from one account only

I am a beginner in ethereum DApp development and I am testing my Contracts in Remix IDE. My question is that can I restrict only one account to pay for all the transactions happening on my application ...
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1answer
36 views

Where, or how, can I programmatically get a complete history of the major cryptocurrencies?

I would like to programmatically get a complete list of the historical: Number of transactions Average Transaction Fee Hashrate Mining Profitability Difficulty Block Time Block Size related to the ...
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1answer
37 views

Contract's transaction count in a certain period

I want to determine the number of transactions of a contract in a certain period. My question is that in the transaction receipt, if we want to say that contract A has x number of transactions will ...
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1answer
34 views

Mist can't run on a testnet?

When I install Mist, and after a bit of loading, it starts downloading the blockchain for the mainnet, but when I change the network, I get an error that it's not connecting. If I try to restart mist (...
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0answers
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
44 views

How can I execute transferFrom function in node js

There is solidity erc865 code function transferFromPreSigned( bytes _signature, address _from, address _to, uint256 _value, uint256 _fee, uint256 _nonce ) public ...
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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
21 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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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
40 views

During the ICO and private sale, Can we lock the bonuses upto 6 months [on hold]

I am writing smart contract and stuck some where how can i block bonuses during the private sale and in ico?
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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
34 views

Can I access last mined block if my node is not there yet?

This might be a stupid question, but I'll ask anyway... I'm currently connected to Ropsten and when I execute eth.blockNumber it says 1853682 (I'm like 300000 blocks away from current last mined ...
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1answer
39 views

Initial Genesis difficulty on an ethereum clone

I've created an ethereum clone that i hope someday can become a public blockchain. This is working good so far, however i have a question regarding the initial setup for once i set this live. If i ...
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1answer
39 views

How to increase stored block states from 128 to 10 000 in Geth?

AFAIK Geth preserves states for the last 128 blocks by default. I would like to keep states for, say 10000 blocks (not turning myself into archive node). Is it possible?
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1answer
40 views

Key-value immutable storage: on-chain vs IPFS

I'm currently working on a D-App for a client. It's basically a temper-proof immutable storage of 'objects', each object being defined with 8 key-value pairs (strings) and a collection of pictures. ...
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0answers
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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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
43 views

Are state changes reversed if the contract “crashes” during execution?

Are state changes reversed if the contract "crashes" during execution? I know that state changes are reversed, if the contract runs out of gas during execution. However, are state changes also ...
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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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0answers
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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2answers
195 views

Quorum 7nodes example unable to attach to geth node 1,2,4,5,6,7 but node 3 is working

Quorum 7nodes example all of sudden gave fatal error unable to attach to remote geth. Problem: can't attach to geth node Every time I import metamask account to geth node (using personal.importRawKey(...
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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
28 views

Whats a good ETH notary service since BTC based OP_RETRUN txns are taboo?

I want to notarize a SHA256 hash of a document I have. Before ETH I would have used a BTC OP_RETURN transaction service. Since BTC is trying to reduce notary spam, what would be a good ETH notary ...
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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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3answers
1k views

Confidentiality in Blockchain

Can Blockchain miners see confidential transaction information? Since they have the public key, they decrypt the transaction for the purpose of verification. So if I am mining in Ethereum, I can tweak ...
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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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7answers
15k views

Question on the terms 'distributed' and 'decentralised'

I am writing a paper on distributed ledger technologies, an umbrella term I have borrowed to put everything that has any relation to blockchains and distributed consensus. Under this umbrella term I ...
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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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1answer
44 views

Do we have to compile and deploy our contract to ethereum each time we start a test rpc?

I'm trying to develop a voting application, I have successfully compiled the app and also deployed it to ethereum blockchain. Now I've closed the test rpc and node console, and when I restarted node ...
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2answers
51 views

Decentralizing DNS using Blockchain

I intend to do a project on Decentralizing DNS using Blockchain. As I was researching this topic, Namecoin was a name that popped up a lot. On searching further, I got to know that Namecoin hosts ....
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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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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
43 views

How to automate blockchain transactions of users without having to ask them to enter wallet addresses?

I am working on a game with an in-game currency. The goal would be that when a player buys something, he only have to click on buy, without having to enter the public address and so on. Are smart ...
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2answers
44 views

Is there any other blockchain project that implements smart contract

Quite new to blockchain so my question maybe somewhat stupid. I have a blockchain project, where smart contract is required but it also has special requirement such as Proof-of-Importance. I have ...
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1answer
42 views

Integrate more then one user with one ethereum account

I have many users inside the organization and I want to use same ethereum account for all the users , but with different usernames, so it there anyway to do that ?