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1500 questions
20
votes
2 answers
What happens when a smart contract gets several similar calls in the same block?
What happens when a smart contract gets several similar calls in the same block?
Consider for instance this greeter:
contract greeter {
string name;
function setName(string name_) {
name = name_;
}
function getName()…
Matias
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20
votes
2 answers
Deploying the Greeter contract via the geth CLI is not registering in my private blockchain
I am running a local private Ethereum blockchain using:
geth --networkid 60098 --genesis CustomGenesis.json --nodiscover --maxpeers 0 --rpc --rpccorsdomain "http://localhost:3000" --datadir "./data" console
It runs fine. I can mine some coins to…
Bill LaPrise
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20
votes
2 answers
How can I verify a signature with the web3 javascript API?
Using the javascript web3 API I can create a signature like this:
> web3.eth.sign(eth.coinbase, "0xdeadbeef")
"0xd3fe64b6f0920593cc4afb1321d592ae91e25fe1a0216e9002a4a6580fb2698c5ec62491c62557b8cc8f64533a5097b3ffb68208952b30cb27ed0a56ae21682201"
Now…
J-B
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20
votes
1 answer
How can I reverse or cancel a transaction or recover lost ethers?
Transactions (using a smart contract like a token or sending ether), by design, are immutable on the blockchain. What methods can be used to (more or less) unilaterally reverse a transaction made by myself or someone else? Situations where one might…
lungj
- 6,680
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20
votes
1 answer
Steps to deploy a contract using MetaMask and Truffle
i'm noob, I want to deploy my contract on Ropsten network with MetaMask & Truffle, plz explain to me the steps to deploy it.
TahaBA
- 819
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20
votes
3 answers
How does Oraclize handle the TLSnotary secret?
Oraclize claims to offer a provably honest secure retrieval of a webpage by taking advantage of TLSnotary (a service that allows an auditor to verify if a specific web page was accurately retrieved)
The purpose of Oraclize seems to be to make this…
Jeff Coleman
- 22,059
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20
votes
3 answers
How to validate a private key?
I could not find any library that, given an hex value, returns true if the given string is a valid ether private key.
Any hints?
Advanced
- 375
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20
votes
2 answers
The Unicorn Mystery - Solidity fails to decode valid UTF-8 encoded bytes
The Ethereum Foundation has the Unicorn token to encourage donations, and the unicorn emoji is represented by three bytes. How in the world did they do that?
I know that Solidity supports unicode escapes, so something like \u2934 in a string is…
user9402
20
votes
2 answers
Is there a way to disable a warning in solidity code?
I'm writing unit tests for some contracts and in some of the tests I'm generating a warning on purpose and solc will display this warning when compiling.
Is there a way to disable warnings in solc for the purpose of a test.
Something equivalent to…
Ismael
- 30,570
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20
votes
4 answers
Synchronisation failed, dropping peer
Whenever I attempt to run geth on the command line, it seems to have trouble syncing with the blockchain. I am absolutely a novice so I could be completely overlooking. I am getting these warnings continuously(This is run on testnet):
WARN…
user3376899
- 301
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- 3
20
votes
2 answers
isContract function using EVM assembly to get the address' code size
My problem is that I need to make sure my contract processes only the transactions coming from EOA (externally owned accounts). For this I need to determine the type of account I'm dealing with. In this question I found a solution, here's the…
manidos
- 4,298
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20
votes
4 answers
How do Ethereum clients generate unique addresses?
How do Ethereum clients, like Ethereum Wallet or Eth-Lightwallet, generate unique addresses that haven't been used before, and what is the likelihood that these addresses have been used?
Alan Wunsche
- 1,655
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20
votes
5 answers
Is there any safe way to send money from a cold wallet, using an untrusted computer?
You have 2 computers. One is 100% offline and, thus, trusted. Other is online. Private keys are stored on the offline computer and the online computer has no access to it. Is there any way to sign a transaction using the offline computer, then…
MaiaVictor
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19
votes
2 answers
Can a contract's internal storage keep increasing forever?
In other words, is there a limit on the amount of storage a contract can hold?
Suppose a field is an Array for instance, and the contract has a method for adding items. Can I keep calling the contract so it adds more and more data?
Fernando Tiberti
- 2,299
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19
votes
2 answers
ValueError: {'code': -32000, 'message': 'only replay-protected (EIP-155) transactions allowed over RPC'}
Good afternoon,
after having been developing a blockchain web app for some months, it's the first time I get this error when making a transaction.
ValueError: {'code': -32000, 'message': 'only replay-protected (EIP-155) transactions allowed over…
Busto
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