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Cryptocurrency Development Ethereum

Why do we have to put ‘hex’ at the end of this function? Buffer.from(‘key’ , ‘hex’)

I know that this line of code: Buffer.from(‘key’, ‘hex’) Converts a string into its binary representation. My question is: what does adding the ‘hex’ at the end do? I am confused, since the key is already in hexa-decimal, why would we want to specify that if the function can work on any string?

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Bitcoin Cryptocurrency Development

how to allow certain rpc commands through remote node?

I’m running json rpc on 0.0.0.0 and i would like to limit this to few commands only. How do i do that ? is it possible to do it using bitcoin.conf file? Thank you.

Categories
Cryptocurrency Development Ethereum

Problem with understanding the solution for Transaction Ordeing Vulnerability

For the following paper, I can’t understand the text written below: https://arxiv.org/pdf/1806.01143.pdf Our violation pattern checks that the amount of the call instruction is determined by a value read from the storage, whose offset in the storage is known (i.e., it is constant), and that this value can be updated. My question is that the […]

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Cryptocurrency Development Ethereum

Compliance and Violation patterns

I have downloaded the slides from the site: [Compliance and Security patterns It says No writes after calls. I can understand this concept. It’s a remedy for reentrancy problem. But it shows compliance and security patterns in some technical language related to Datalog or to some language related to software representation. Can some body please […]

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Cryptocurrency Development Ethereum

Why does Infura Ropsten websocket filtering event timeout?

When listening events via Infura Ropsten websocket, web3.py implementation timeout while web3.js succeeds. The demo can be cloned from — https://github.com/jerryji/ropsten_wss_timeout_demo After installing requirements, which basically boils down to web3 only for both Python and JavaScript — pip3 install -r requirements.txt npm install export your Infura Project ID — export PROJECT_ID=<Your Infura Project ID> Running […]

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Cryptocurrency Development Ethereum

web3js subscribe giving same result twice

When I subscribe to the transaction using web3j, why it give me 2 identical result and receipts: const subscription = web3.eth.subscribe(‘logs’, { address: ‘a’ }); subscription .subscribe((err, res) => { if (!err) console.log(‘RESULT’, res); }) .on(‘data’, async txHash => { const receipt = await web3Http.eth.getTransactionReceipt(txHash.transactionHash); console.log(‘RECEIPT’, receipt); How can I get just one record or […]

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Cryptocurrency Development Ethereum

Error: invalid address in solidity constructor

I get a huge error message (~1MB) starting with Error: invalid address (arg=”_readAccess”, coderType=”address”, value={“constructor”:{“contractName”:”SenderAccess”,”abi”:[… when executing a test written in TypeScript: it(“should be possible to create such an option”, async () => { const accessControl = await SenderAccess.new(); // OK const validator = await NumberRangeValidation.new(1, 5); // OK // This will crash const option […]

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Cryptocurrency Database Development Ethereum

Bad Block Corrupted Chain-state Database due to geth bad shutdown by user. need repair command

Bad Block , Corrupted Chain-state Database due to geth bad shutdown / improperly terminated. What is the repair command and format of command to repair or fix my “geth –syncmode fast –datadir D:\folder\EthereumGethChain” INFO [11-22|05:51:50.137] Importing sidechain segment start=4684119 end=4685311 ERROR[11-22|05:51:51.651] #### BAD BLOCK Chain config: {ChainID: 1 Homestead: 1150000 DAO: 1920000 DAOSupport: true EIP150: […]

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Cryptocurrency Development Ethereum

What does it mean to serialize a transaction?

In tx library there is a function: serialize() that “serializes” your transaction object. You can then convert that serialization into hexa decimal string, and use it to send the transaction with the sendSignedTransaction() method. My question is: what does serializing a transaction object mean? and why is it necessary to do this?

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Bitcoin Cryptocurrency Development

New cryptocurrency blog,how to buy btc using paypal?

how to buy btc using paypal? Investing in bitcoin has never been easier. Most people buy bitcoin in one of three ways: Bitcoin exchanges: the most popular way of buying bitcoin is through online exchanges, typically requiring proof of identity, and charging a small transaction fee. See our recommended list of exchanges https://cryptocrow.net/