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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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47 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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0answers
6 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
160 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 ...
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0answers
16 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
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 ...
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1answer
54 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
140 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 ...
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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
245 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
28 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, ...
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1answer
32 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 ...
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1answer
751 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 ...
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1answer
35 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
190 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?
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1answer
141 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
8 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
23 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); ^----------...
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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 ...
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1answer
127 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
20 views

how? blockchain fund transfer error .. missing funds [on hold]

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
117 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 ...
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1answer
41 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
930 views

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

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
25 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 ...
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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 ...
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1answer
124 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, ...
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1answer
95 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 ...
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0answers
32 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 ...
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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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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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0answers
23 views

Error Updating Security Message When Trying To Whitelist Address When Using Infura [closed]

I'm currently trying to whitelist a contract address within Infura, however I keep getting this error message and being logged out. I have tried it from different IP addresses, different machines, and ...
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2answers
251 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]; ...
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3answers
510 views

Are blockchains copied or distributed between nodes?

The following guide mentions that blockchains allow digital information to be distributed but not copied: By allowing digital information to be distributed but not copied, blockchain technology ...
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0answers
21 views

How to get the value from the frontend form and save value to the blockchain using +web3 1.0.0-beta.37 + reactjs

I am writing my first Dapp and want to save the value of the form to the blockchain. I am Using React and web3 js 1.0.0-beta.37 on the frontend. Also I am new to react. Following is my App.js ...
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0answers
12 views

Could the parity-ethereum client incorporate doing range proofs in the ethereum blockchain?

I want to be able to prove that I have stored a number that is in the range of a minimum and maximum value, (a range proof) without revealing the number, and put the value into the ethereum blockchain,...
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1answer
433 views

web3 not connecting to Infura / Rinkeby Testnet

I've successfully deployed my Smart-Contract to the Rinkeby TestNet via Remix. Everything works perfectly from within Remix. But when I try to get my web DApp to fire methods in my Smart-Contract - ...
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1answer
29 views

How to know if the token is ERC20 or ERC233?

as I stated on the title because I am very confuse on how to know if the token is ERC20 or ERC233. I bought Thore Cash on Mercatox and I didnt know if it is ERC20 or ERC233 but they said they ...
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2answers
40 views

How blocks in a blockchain are identified that store concerned policy?

I am working on blockchain. My project is to store Role based access control policies(user-role assignment and role-permission assignment) in blockchain. Policies are written in 2 dimensional array (...
1
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1answer
43 views

Access deployed smart contract using web3.js

I am new to Etherium smart contracts. I have created a smart contract and deployed it on https://kovan.etherscan.io. Now I am trying to access this contract from node js. below is my code but I am not ...
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1answer
50 views

ganache-cli: how to persist new created accounts

I start my service by: ganache-cli -d --gasPrice 0 -q --db=./db This persists my 10 defaults created accounts, but when I create new accounts using Web3: web3.eth.personal.newAccount('password') ...
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1answer
149 views

Python state channel client

Stumbled upon this piece of Solidity code which is an Ethereum payment channel : https://github.com/mattdf/payment-channel How am I to write a Python client that interacts with it over Web3 ? What ...
1
vote
1answer
313 views

Ethereum gas limit issue while sending transaction from web3 client (private network)

I have setup a private Ethereum system using geth. And am running a client that uses a web3.js file to connect to the Ethereum system. While trying to send a transaction or call some contract function,...
0
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1answer
119 views

How my Cryptocurrency Exchange supports Fiat Currency?

Which mechanism is used in Cryptocurrency for converting Fiat currency into Cryptocurrency? Do they maintain stock for particular Cryptocurrency? or they have tie-ups with organisations like (ethereum....
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2answers
318 views

How calldata is stored in memory?

when I execute this: bytes8 h = 0x000008dfe2f440000733c; t.call.gas(0x7e0b0)(bytes4(keccak256("enter(bytes8)")),0x8dfe2f440000733c0000000,h); the calldata is : 0: ...
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3answers
20k views

What is an uncle/ommer block?

The Ethereum blockchain is described as containing "ommer" blocks, usually called "uncle" blocks by the general public. What is an ommer/uncle block, and why are they needed?
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2answers
119 views

Is Merkle tree applicable at block level also?

As per my understanding, Merkle tree is applied in case of transactions. Through Merkle tree we generate root hash transaction from all the transaction present in a block. So does it work the same way ...
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1answer
15 views

What does it mean that Solidity can encode arbitrary state transition functions?

From Ethereum White Paper: "What Ethereum intends to provide is a blockchain with a built-in fully fledged Turing-complete programming language that can be used to create "contracts" that can ...