59 votes
Accepted

What is Gas Limit in Ethereum?

In Ethereum, gas is a measure of computational effort. To each operation, a fixed amount of gas is assigned (e.g. adding two numbers costs 3 gas, calculating a hash costs 30 gas, sending a transaction ...
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  • 1,896
10 votes

Is it correct to say that Bitcoin has a virtual machine in the same way as Ethereum does?

"Virtual machine" in this context is really just a fancy word for bytecode interpreter. Bitcoin's script language is certainly far simpler than Ethereum's EVM, and its functionalities are in ...
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9 votes
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Check password for ethereum wallet

You could check by starting a geth console and using the personal.unlockAccount function: $ geth console > personal.unlockAccount("address", "password")
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  • 268
9 votes
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In Ethereum, what is an uncle block?

An uncle is a block that, in bitcoin, would be considered a stale block because it is not on the longest chain (it's an alternative block at the same height as your parent). Ethereum incentivizes ...
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9 votes

What are the differences (and value adds) among all the different Crypto Currencies?

99% of altcoins claim an "innovation" that is broken or unproven. I would say that the first thing to do is look at unique codebases that aren't based on Bitcoin, which basically means (besides ...
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8 votes

What is Gas Limit in Ethereum?

The current gas limit can be checked on the network stats page. It's currently 3,141,592 (pi million). The gas limit per block is not fixed, though. The number of contract calls and standard ...
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  • 1,376
8 votes
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Is there a pro vs con chart comparing Bitcoin's Rootstock vs Ethereum Smart Contract system?

Rootstock's smart contract features are identical to Ethereum's, both use the EVM. Contracts on Ethereum are deployable on Rootstock, and vice versa. They start to differ when you look at the ...
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  • 1,034
8 votes

How does using a Turing-complete programming language compromise the security of the network?

It is much easier to formally verify the behavior space of Bitcoin script vs. Solidity. For example, the DAO project suffered from reentrancy vulnerabilities, given that one could not predict the ...
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  • 2,423
7 votes

Is there a way to access Ethereum Smart Contract's variables by name in JavaScript?

Note that this question has been automatically mapped to reddit and answered there. If you declare your state variables as public, a function to read their values will be automatically created by the ...
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  • 256
7 votes

What are the differences (and value adds) among all the different Crypto Currencies?

A very large majority of these altcoins are essentially scams. There is a cottage industry that takes a coin, changes something minor (name, logo), and releases it with great fanfare, enticing people ...
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  • 786
7 votes
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Does bitcoin have the potential to be subject to a hard fork where miners are forced to choose which fork they will accept, like Etherum?

Yes, Bitcoin could also be subjected to a hardfork. In fact, there are members of the Bitcoin community that feel so strongly that the blocksize should be increased that they are proposing to do just ...
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7 votes
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Does Bitcoin Blockchain solves Byzantine General Problem?

The Proof of Work algorithms is a probabilistic solution to the Byzantine General's problem in the case where traitorous generals represent strictly less than 50% of the generals. To simplify, the ...
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  • 231
7 votes
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If the nonce is 32 bits why the proof of it is difficult?

The vast majority of the time, none of the 2^32 possible nonces in a particular block header template will result in the header having a hash that meets the proof-of-work target. In fact, the ...
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6 votes

Who pays the fees for transactions initiated by a smart contract in Ethereum?

A smart contract can only initiate a transaction when it receives a transaction from either another contract or a user. Thus, all transactions must originate from some user transaction, and it is this ...
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6 votes

What is the approach to calculate an Ethereum address from a 256 bit private key?

Start with the public key bytes (a bytestring of length 64) Of that public key, take the Keccak-256 hash used ubiquitously by Ethereum (make sure you get that right, as the ultimately standardized ...
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6 votes
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Does ethereum run on the bitcoin blockchain?

Bitcoin and Ethereum have different and unique blockchains. They have no relationship (other than the fact that Ethereum and all other cryptcurrencies based their design on the Bitcoin blockchain).
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6 votes

Etherium based tokens

It is completely different. Ethereum offers a standardized way to create new tokens on its blockchain called the ERC-20 protocol. ERC-20 is not a piece of code, software, or technology. Rather, it is ...
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6 votes
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In what sense does the security model of proof-of-stake require users to "log on to the internet every few months"

What Vitalik is talking about is the Slasher algorithm that he designed which punishes the block signer if he attempts to create a fork in the blockchain. However the way that slasher works is that ...
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5 votes
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Why is a short blocktime considered to be unsafe?

The shorter the blocktime the more time is lost by the relaying of blocks in relation to the average blocktime. A very short block interval therefore makes SPV mining (i.e. mining empty blocks without ...
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5 votes

Can an Ethereum contract be updated without having to be re-submitted?

You can separate concerns - have a contract that the users interface with and that has a reference (an address) of another contract that contains the actual logic. Then, you can control the interface ...
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5 votes

How does Ethereum domain registration works?

So the whole point of a name reg contract is not to send transactions, rather its sole purpose is to build up a database which other nodes can then query. Ethereum smart contracts have immutable ...
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5 votes
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Does Ethereum support the features necessary to create the Lightning Network?

They don't need to support those. As mentioned by Roman you could build the entire LN in one contract. You can even implement the LN Relative OP_CHECKLOCKTIMEVERIFY requirement in a much better way. ...
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5 votes
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What is the DAO, and what is its connection with Ethereum

So what is the DAO's connection with Ethereum, and what is its purpose? The DAO was a decentralized autonomous organization designed to invest in DAPPs built on Ethereum Why is the operation of the ...
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  • 271
5 votes
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Problem of colored-coins/assets and other coins with a parent/child relationship of paying for fees with only the parent currency

It's definitely a common problem found in a lot of those platforms that make it easy to create your own colored coin/token. Asking users to acquire the native token, such as Bitcoin with Counterparty ...
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  • 281
5 votes
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What database engine does Bitcoin and other top altcoins use?

It depends on the implementation. The network itself does not have a database engine. Bitcoin Core and software derived from it (most altcoin software is derived from Core) uses LevelDB to index the ...
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5 votes

How are eth transaction faster than btc?

Most simple and foreseen reason: Bitcoin's blocktime is set at 10 minutes, while Ethereum has a block every 10-20 seconds, making it much faster. See Ghost protocol, https://www.cryptocompare.com/...
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5 votes
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When does Ardor smart contracts come into effect and how does it work compared to Ethereum, EOS, and Lisk?

First off, Lisk doesn't have full turing-complete smart contracts so there isn't much of a comparison on that front. Key shortcomings of existing frameworks like Ethereum can be summarized by five ...
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5 votes
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Why are there ETH addresses in bitcoin wallet.dat?

Ethereum addresses are the trailing 20 bytes of keccak256(public_key). In other words, ethereum addresses are any collection of 20 bytes. 0014{20 byte payload} in Bitcoin is the redeem script for a ...
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4 votes
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Ethereum vs NXT Comparison Chart?

I have composed one of the more comprehensive comparison charts of the various Crypto 2.0 platforms over at http://tiny.cc/Crypto (or a more direct link). It currently has pretty comprehensive ...
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4 votes

How to delete an element of an array in an Ethereum contract?

Refer to the documentation: delete myArray[arrayIndex];
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