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Cryptocurrency Ethereum Mastering Development

Adding Struct to Array – Invalid OpCode – Solidity 0.6

I’ve been wreaking my brain on this for a while, could use some help. Bottomline, the newProposal function throws an VM Exception while processing transaction: invalid opcode error. The puzzling thing is that this function was working fine with Solidity 0.5, but not with 0.6. Here is what I’ve attempted so far, any further insight […]

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Bitcoin Cryptocurrency Mastering Development

College Economics Student in Support of Crypto Looking for Live Hashrate Data

I am a college economics student doing a Thesis project in support of the long term viability of Crypto. Does anyone know where I can get live Hashrate data for free or for sale? I appreciate it – thank you!

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Cryptocurrency Ethereum Mastering Development

String To bytes Error

I am trying to take user input strings and convert them to bytes32 and bytes5 for a contract built in Solidity 5.11, I tried 32 and 5 character long random strings respectively however they are not working, is there an inbuilt function for web3 to convert Strings to bytes (either 32 or 5) like web3.utils.fromAscii […]

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Bitcoin Cryptocurrency Mastering Development

Is there a simpler form of BIP32-like key derivation?

I’ve read about BIP32 key derivation functions, and also: Any Elliptic Curve could work in the BIP32 scheme. The only property of a Curve that BIP32 relies on is that a * G + b *G = (a + b mod N) * G, which is true for any Elliptic Curve. (from Is BIP 32 […]

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Cryptocurrency Ethereum Mastering Development

Solidity get() function only returning one string when i ask for all strings in mapping

Can anyone tell why my get() function only returns the string "name" in Remix? I’d like it to return all the values within the users mapping like i’ve defined, can you help me accomplish this? pragma solidity ^0.5.0; contract Profile { struct User { string name; string subtitle; string sdescription; string ldescription; string weburl; string […]

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Cryptocurrency Ethereum Mastering Development

Sending extra data beside or inside a new smart contract

I’m doing a research about Ethereum smart contracts security and I need to send some extra data (for example some json data) beside or inside a new smart contract when I’m deploying that contract on the network. Is it possible and how can I do it?

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Cryptocurrency Ethereum Mastering Development

In Solidity, which value the function type should return?

In Solidity, function type doesn’t have function excuting code body, what’s the value it should return? Example: function eval( function (uint, uint) internal pure returns (uint) f, uint a, uint b) internal pure returns (uint) { return f(a, b); } Which value that f should return for eval return? a or b or others? and […]

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Bitcoin Cryptocurrency Mastering Development

What is the Bitcoin network?

This is a beginners question related to bitcoin. As bitcoin is a system of distributed bitcoin users, and a transaction is being sent to ‘all’ of them – well, what is that network? What IP adresses? Is there a bitcoin databank of bitcoin users? Is there an initial list of some users? How does this […]

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Cryptocurrency Ethereum Mastering Development

err=”authentication needed: password or unlock” in geth

Is this possible that this error "authentication needed: password or unlock" can stop the whole chain because my chain keeps crashing.

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Cryptocurrency Ethereum Mastering Development

Function call browser monitoring of Metamask

While working with different Dapp project, whenever we call some function or any transaction, Metamask automatically detects that call to the contract and provide an interface that builds the transaction and get your signatures. EDIT: As a project, I am trying to build my own little version of Metamask. Till now I am able to […]