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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1answer
119 views

Synchronous call of external contract function in Solidity

I have two Solidity contracts, where contract Caller depends on a second contract Callee. Contract Callee provides a public view function which checks the validity of a string (e.g. an password), ...
3
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2answers
319 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
24 views

Deploy dapp on private blockchain network

i have create a private network with 2 nodes. I have connect an account with metamask from my private network and i have created a full dapp ( contract,front-end). Now i want to deploy the whole dapp ...
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0answers
36 views

Error while importing Libp2p package in blockchain

I have installed some js-libp2p's packages on my Ethereum Blockchain-ipfs project and I wrote some codes like below. const TCP = require('libp2p-tcp'); const MulticastDNS = require('libp2p-mdns'); ...
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0answers
8 views

Do i need to create Checksum in blockchain? [on hold]

I'm trying to develop blockchain application, since it is newly developed do i need to create my own checksum algorithm ?
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1answer
76 views

What would an Etheruem-like blockchain look like if each block were just an IPFS hash?

I see a lot of people tout the enormous benefits of using IPFS as a store of data. Meanwhile, the Ethereum blockchain is over 1TB in size, with quesitonable need to keep the earlier blocks. In ...
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1answer
91 views

How block are validated in a private blockchain

I have running a private blockchain with 4 nodes, and when i'm creating my Dapp, i have specified for the web3 address only one node ( Ip; port, RCP) So, my question is , how the others nodes ...
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0answers
20 views

Time in blockchain and HTML

I'm trying to get time once data is submitted off-chain, since only way to get on-chain is via now to get the block time. Off-chain I'm using "document.getElementById("demo").innerHTML = Date()" to ...
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1answer
14 views

No web3.min.js while download Zip file from Github

I am following a youtube tutorial to make a simple dApp. In this tutorial he is telling to get Web3 from GitHub. I downloaded the Zip of Web3 from the GitHub and i get following folders and file after ...
44
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4answers
19k views

What is the cost to store 1KB, 10KB, 100KB worth of data into the ethereum blockchain?

Whatever is stored in the blockchain is immutable which means I can fetch this data back in the future. As of today (2016-feb), How does one store a 1kb, 10kb, or 100kb or arbitary data/text in the ...
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0answers
18 views

How to compile solidity code in Kali Linux

I have tried to install the remix IDE for compile my codes in solidity, since for some reason the remix IDE don't open online. I executed the codes bellow and give that errors. Sorry anything ...
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1answer
110 views

Accessing older blocks from Geth: Returned error: missing trie node 94d34

When my Nodejs script uses web3 to query a geth node running in a private Ethereum network for an older block, I encounter the error UnhandledPromiseRejectionWarning: Error: Returned error: missing ...
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1answer
104 views

Problems funding Ethereum Wallet

Tried making three separate transactions from two separate wallets (Coinme and Coinbase) each in relatively small amounts (less than $50) to fund my Ethereum Wallet 8.0 for Mac. None have appeared ...
2
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1answer
145 views

Blockchain on Container Platforms

I want to deploy private blockchain with 4 nodes. I am trying to use Kubernetes to create P2P network.I am asked to explore this.I have one question regarding real usage or benefit of Blockchain on ...
0
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1answer
143 views

Converting int to default block parameter

I am using Infura and web3j to query the Ethereum blockchain. My aim is to get information about certain blocks so i'm using the function web3.eth.getBlockByNumber, however it gives me incompatible ...
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0answers
30 views

Why this error occurring when i running my dapp?

I create a dapp using Solidity,Web3Js,Javascript and Html with metamask i always getting this error when i am trying to submit my transition i am getting this error at c (inpage.js:1) at ...
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1answer
73 views

Would this make sense as a smart contract application? Trying to understand features and limitations

I'm starting to read up on Ethereum and smart contracts and some questions are popping up in my mind. I can understand that smart contracts can be used, for example, to make a bet for/against the ...
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0answers
13 views

Can't call contract function in Remix in Web3 provider mode, but it works in Javascript VM

A simple contract for addition, an error is reported when calling the function add in Web3 provider mode: "Gas estimation errored with the following message (see below). The transaction execution ...
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1answer
52 views

How to connect Trust Wallet in Javascript?

I want to use TrustWallet for payments in my project for mobile users. I saw the documents related to TrustWallet web3 API but not getting how to use it in javascript. Can anybody help me with the ...
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1answer
165 views

How to read previous blocks data?

I'm new to block chain technology. I'm trying to store and read blocks using testRPC along web3.js. I'm able to get the latest block data but not able to fetch previous blocks data. Please some one ...
1
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1answer
90 views

how does a smart pool identifies the valid block in ethereum

I have been reading this paper https://eprint.iacr.org/2017/019.pdf. To my understanding, the miners send the shares in batches and later the smart pool verifies the shares with sampling with ...
1
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1answer
56 views

how execute smart contract step by step?

I have a few problems understanding the step of execution of transaction in smart contract. 1-When a user send a transaction to smart contract, this smart contract is not executed immediately instead ...
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1answer
145 views

Implementing Blockchain and Converting Web App to DApp

I have my web-application which is in Angular2 (Front end) and Rails (Back end-API), now I want to implement Blockchain to this Web application, so needs to make it DApp. Here while making the DApp, ...
16
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4answers
8k views

Error “no key for given address or file” when unlocking coinbase account

Using json-rpc eth_unlockAccount() method I can unlock everyone of my node accounts except coinbase. When trying to unlock coinbase account, geth responds with the message: no key for given address ...
2
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1answer
127 views

Solidity cross programming language method calling

I was wondering if it is possible for solidity to call functions of other languages. More specifically, I am planning on developing a basic distributed search engine using the ethereum blockchain and ...
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3answers
247 views

Unlocking Ethereum wallet using Geth JSON-RPC

When I use ETH with JSON-RPC I have error "message": "authentication needed: password or unlock» and If I manually unlock I have other error "message": "insufficient funds for gas * price + value" Any ...
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1answer
30 views

Static difficulty in 1.8.27 for local network

I am having trouble getting geth 1.8.27 to have a static difficulty on a private network. I followed the instructions from here. But when I test it, the difficulty still increases. I tried again, ...
1
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1answer
33 views

How to pass a document as function argument(upload document)

I am working on a project in solidity where I want to generate a SHA256 hash value for the document. So which means when I pass a file to a function the function should return the hash value. can ...
10
votes
1answer
753 views

How can I reliably induce a blockchain fork for testing purposes?

I would like to reliably induce a fork on a private testnet so that I can test the behavior of off-blockchain code that interacts with contracts. (see related questions as to why I would want to do ...
1
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1answer
41 views

Solidity Error Address / Address Payable

I'm currently learning solidity programming to create a basic smart contract based on a 2018 tutorial where solidity was using version 4. I'm currently using truffle v5.0.21. I understand that there ...
4
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2answers
207 views

Offchain vs Sidechain vs StateChannel

What are the main differences between off-chain, sidechain and state channel? And what are the use-cases of all of these?
2
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1answer
146 views

Connecting to blockchain on azure using web3.js and websocket

right now, I am trying to write a service using web3 which will 'subscribe' to all 'perndingtransactions' on blockchain to perform further actions. web3 documentation says that 'Httpprovider' cant be ...
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0answers
13 views

Problem connecting web3 via websocket to node with nginx

we are trying to connect to a geth node via WebSockets to be able to subscribe to contract events. This node is created with docker and this docker uses nginx as a proxy. We can connect easily with ...
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0answers
27 views

Solidity: TypeError: Member “unbond” not unique after argument-dependent lookup in contract super EthGatedMarket

I'm getting this error: TypeError: Member "unbond" not unique after argument-dependent lookup in contract super EthGatedMarket. super.unbond(msg.sender, gatewaySpecifier, quantity); ^----------...
6
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5answers
3k views

Where is blockchain scalability bottleneck?

There is a moment I still don't understand about blockchain. I've never seen ethereum client coniniously under 100% CPU or network load. So why isn't it possible to process transactions faster? I ...
1
vote
1answer
129 views

Installing Ganache GUI on windows 8.1

How to install Ganache UI on windows 8.1 ? I downloaded from Official website but after downloading i am unable to install it on my machine. I tried to install it through power shell but facing ...
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0answers
21 views

how? blockchain fund transfer error .. missing funds [closed]

How is this possible on the blockchain? Sent 275.80 ether from Binance, transfer confirmed, to another exchange, block chain confirmed. Funds deposited were 0.04 ether, not 275.80 !! This was 3 weeks ...
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3answers
134 views

Can't compile old solidity contracts(version 0.4.17)

I'm new with blockchain development. I'm working on an old project which use solidity 0.4.17 and truffle ^4.0.0-beta.2; These versions were in the package.json file of the project. When I installed ...
1
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1answer
43 views

Three questions

I have recently become interested in crypto and after much reading on Ethereum I still have three burning questions that perhaps some of you can help with. Apologies in advance as some of these might ...
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3answers
949 views

How can I use machine learning with smart contract? [closed]

I'm new in programming Blockchain. I want to make a smart contract with machine learning, a simple case. I know how to create a solidity contract, but I do not know how to add learning to the contract....
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1answer
190 views

Unable to interact with DApp deployed on quorum

I am unable to interact with contract using Dapp deployed on Quorum blockchain (using metamask). I am following "https://truffleframework.com/tutorials/building-dapps-for-quorum-private-enterprise-...
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0answers
33 views

Error: The data field must be HEX encoded data

I am trying to make a simple dApp by using a tutorial. I am using the following command ; npm install ganache-cli web3 so that we can use web3 to get fake ethereum nodes/accounts by connecting it ...
0
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2answers
38 views

Is Ethereum a common blockchain for all type of smart contracts (several thousands)

I have read that full nodes run all the contracts(several thousands) to verify them so aren't they using too much energy (and also thus spending money) to verify each and every contract that is ...
0
votes
1answer
125 views

Unable to send ether to account

I am trying to send ehter using this code web3.eth.accounts.wallet.add(privateKey); web3.eth.sendTransaction({ to:someAddress, from:onwer, value:amount*1, ...
0
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1answer
96 views

testing the hello world application on a different computer when the compute crashes/node not working

I am new to the blockchain technology. I want to test the blockchain functionality of a decentralized ledger. I have created a hello world smart contract(on solidity, geth, mist browser) on computer ...
0
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0answers
42 views

Can't connect to localhost:8545 while using ethereumjs-testrpc web3?

I am developing a simple Voting dApp by following a tutorial. In this tutorial we are using npm install ethereumjs-testrpc web3 so that we can get the fake nodes of Ethereum. For that i first ...
0
votes
0answers
8 views

How can I combine Quorum and Zero Knowledge Range Proofs

How can I combine Quorum and Zero Knowledge Range Proofs I have 20 years of experience at java JEE coding, and 10 years in devops as well, but no experience with blockchains, or the Go language. I ...
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0answers
7 views

What repo in loom do I fork to create my own sidechain?

I am trying to create a sidechain. I believe I need the code for the node that supports the sidechain. How many repos will I need to collect to properly start my own sidechain? Ideally a proof of ...
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vote
1answer
115 views

Is there an explorer like Etherscan for Remix JS VM sandbox blockchain

I created a contract and did some transactions. I would like to explore the transactions in the sandbox blockchain in my brower (Chrome). But the tx hash is not found in the REMIX VM Debugger http://...
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2answers
257 views

Problem in fetching return values in solidity contract function using web3 js

solidity function: function getCredentials(uint id) public constant returns(string,string,uint) { address ad=acadr[id]; uemail=email[ad]; ulocation=location[ad]; ugid=gid[ad]; ...