Questions tagged [addresses]

Addresses are the particulars of names, domains or accounts on the blockchain.

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143 votes
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How are ethereum addresses generated?

What criteria does a valid Ethereum address need to fulfill? Is it just a random number in hexadecimal? Or does it need to be derived in a specific way, according to some cryptographic algorithms? ...
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115 votes
6 answers
54k views

How is the address of an Ethereum contract computed?

How is the address of an Ethereum contract computed? What use cases are there for knowing a contract's address in advance?
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79 votes
9 answers
85k views

How can I check if an Ethereum address is valid?

I've read many times that you should never input an address by hand unless you want to accidentally send Ether into no-mans-land. I'd like to know what those checksums might be. Is there a way to tell ...
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70 votes
3 answers
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Is Ethereum wallet address case sensitive?

I sent some amount of ETH to a wallet. I checked the wallets balance on ether chain. I entered the address in the search field and noticed both lowercase and uppercase versions of the address seemed ...
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59 votes
5 answers
42k views

Get public key of any ethereum account

Can I somehow get the public key of an ethereum account knowing just the corresponding ethereum address (e.g. 0x54dbb737eac5007103e729e9ab7ce64a6850a310)?
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55 votes
4 answers
17k views

Why don't Ethereum addresses have checksums?

A checksum, similar to its use in Bitcoin addresses, can primarily prevent mistyped or invalid addresses from being used, before a transaction with an invalid address is constructed. Why don't ...
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49 votes
3 answers
28k views

What's the difference between 'address' and 'address payable'?

I saw a Solidity smart contract where some variables were declared with the type address and some were declared with the type address payable. What are the differences between the two? Do they store ...
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44 votes
3 answers
72k views

How to backup mist wallets?

I know I can backup the keystore files from my running ethereum client which holds my accounts. But how can I backup wallets created with mist? Is it enough to write down the public address where the ...
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34 votes
2 answers
16k views

How to encrypt a message with the public-key of an Ethereum address

I am writing some code in nodejs/browser. I have successfully created ethereum-addresses with the secp256k1-library. I was also able to sign and verify messages. Now I want to encrypt/decrypt a ...
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32 votes
5 answers
17k views

How to detect if an address is a contract?

I'm interested in knowing whether any particular address is a contract address or a standard address. There have been similar questions on the topic, but I'm not looking to detect whether an address ...
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32 votes
2 answers
10k views

Is each Ethereum address shared by (theoretically) 2 ** 96 private keys?

Summary This is an extended question to How are ethereum addresses generated?. In Ethereum, a private key is 256-bit long, but an address is only 160-bit long. By "Pigeonhole Principle", it ...
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30 votes
5 answers
18k views

How does a contract find out if another address is a contract?

Is it possible, from within a contract written in Solidity, to check if a contract is placed on a specific address or if this address does not contain any code?
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29 votes
5 answers
32k views

Convert address to string

In Solidity, how can I convert the sender address to a string? The comments in How to convert an address to bytes in Solidity? did not provide a working solution
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28 votes
4 answers
28k views

Calling function from deployed contract

I want to know how to instantiate an existing contract deployed on the blockchain using its address. e.g: contract A { function f1() {} } A is deployed on the blockchain, and in contract B I ...
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27 votes
1 answer
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Cannot perform write functions in smart contract - invalid address?

I have the following simple smart contract... contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) ...
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25 votes
3 answers
15k views

Difference between Ganache and Truffle

What is the difference between this two? I understand that Ganache is like a fake blockchain, but Truffle has that too ? What are the limitations of each and under which circumstance we use either ...
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  • 395
22 votes
3 answers
6k views

Account uniqueness guaranteed?

When we create an account in the Ethereum main network, how does the protocol guarantee the unique address of an account? Since even if we are not connected to the network we can create an account, is ...
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22 votes
3 answers
21k views

How to list transactions from account address?

I have a small service where people can exchange cryptocurrencies. Every user has its own Bitcoin, Litecoin, etc address for balance deposit. Now I want to add Ethereum. So I thought I will create ...
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21 votes
2 answers
8k views

Is it safe to reuse Ether addresses?

I believe it's viewed as unsafe in Bitcoin because of the way transactions are signed. Is this also true for Ether addresses?
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20 votes
4 answers
25k views

Can solidity contract arrays receive arrays of addresses as parameters?

This question is related to this one but using address arrays instead of strings. Does solidity support arrays of addresses to be passed as method arguments? contract C { uint256 hexVal = 0xABCD; ...
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19 votes
4 answers
30k views

Ethereum Address vs Public Key

I'm creating an ethereum wallet and I'm a bit confused with the concept of public key vs address. I understand that the Address is a hashed version of the public key, but when I'm generating a new ...
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19 votes
4 answers
6k views

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?
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19 votes
2 answers
11k views

How to use address.call{}() in Solidity

I have seen here and several other places that the correct way to send ether from a contract to an address is to call the .call{}() method. Then here, I have seen the method being used with arguments, ...
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19 votes
1 answer
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How Can I Add My Name Next To Address On Etherscan?

I'm wanting to set up a charity and want to use a public wallet for accepting donations with on Etherscan where I can have a displayed name next to the wallet like this: How Can I Add My Name Next To ...
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17 votes
6 answers
17k views

How to convert an address to bytes in Solidity?

What is the recommended way to convert an address to bytes in Solidity?
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16 votes
1 answer
3k views

Getting the wrong address back from ecrecover

When I sign a string using the following code I get back a different address to the one I signed with. The address returned is different for different strings. const util = require('ethereumjs-util') ...
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15 votes
3 answers
11k views

Ethereum Vanity Address generators

Are there any Ethereum vanity address generators available other than: Vanityreum (python) Vanieth (go) Which is the fastest? Can they be optimized further? What is the use-case of vanity ...
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14 votes
3 answers
5k views

Multiple transactions from same address

I would like to create multiple transaction from the same address at the same time. Since every transaction needs nonce (tx count of the sender address) I can ask geth for the current count and create ...
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14 votes
3 answers
71k views

How to create an Ethereum address?

I know basically zero about Ethereum, block chain etc. I have Augur reps. I have been asked to create an Ethereum address for the sale augur site. I don't have the slightest idea how to generate an ...
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14 votes
4 answers
9k views

What Hierarchical Deterministic (HD) wallets are available for Ethereum?

A Hierarchical Deterministic (HD) wallet has some nice features such as easier backup (instead of needing to backup multiple keystore files and the passwords for each of them). Are there any ...
13 votes
2 answers
13k views

Should I always put 0x at the start of Ethereum addresses?

Should I always put 0x at the start of Ethereum addresses? Sending ether to addresses without 0x seem to work perfectly fine. when sending to an address, do you include the "0x" before the rest of ...
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13 votes
1 answer
7k views

Is an Account in MetaMask the same as an Ethereum Account (EOA)?

First, my setup: I use the Azure Ethereum Consortium Template, which creates one transaction node and two mining nodes in my configuration. I use MetaMask Chrome plugin to accept transactions, which I ...
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12 votes
1 answer
12k views

What does address(0) mean? [duplicate]

Referring to this link: https://theethereum.wiki/w/index.php/ERC20_Token_Standard looking at the last contract. (Line 130) function totalSupply() public constant returns (uint) { return ...
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12 votes
2 answers
6k views

Is address(this) a valid address in a contract's constructor?

When does a smart contract's address first become valid? Is the address during the execution of the contract, or only after it's been fully instantiated and initialized? In other words, is a contract'...
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11 votes
3 answers
21k views

How to check for valid contract address using web3?

I am simply trying to avoid the error: Error: invalid address web3 throws this error when the address to a contract is not valid. Is there a way to catch this error ? I am using web3 in a nodejs ...
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  • 579
11 votes
2 answers
32k views

The difference between contract address and wallet address

Disclaimer: this is a rather long question. To my understanding, contract address and wallet address are two profoundly different concepts, with the only thing in common being the fact that they are ...
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11 votes
1 answer
17k views

Solidity: How to specify a (hard-coded) address as a literal

I am defining a contract and I want to ensure a particular member variable can only be modified by me. So, specifically I want to ensure that if someone else deploys one of my contracts, then they ...
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11 votes
1 answer
2k views

How to generate a vanity address for a smart contract to be deployed on?

I am aware of the possibility to generate vanity addresses for normal accounts. However, how is possible to generate vanity addresses for external owned accounts (which host smart contracts)? I'm ...
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11 votes
4 answers
27k views

Is there a simple Ethereum address generator that consists only of private key and public key?

I can go to https://www.bitaddress.org/ , download their software to my system, disconnect my system from the Internet, then move my mouse over their page randomly to generate entropy and then get a ...
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11 votes
2 answers
4k views

Some characters in Ether addresses have changed to capitals after upgrading Mist

I recently upgraded Mist from 0.3.9 to 0.5.0. I have noticed that the capitalisation of some of the characters in my public address have changed. Is this normal?
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11 votes
2 answers
9k views

How to list all the contracts currently on the blockchain?

I know one way to interact with contracts is, in the geth interface, to use the command: eth.contract(ABI).at(Address) But for this I will need to know the ABI and address of the contract in advance....
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11 votes
1 answer
2k views

Why are Ethereum addresses hashes of public keys?

I understand how Ethereum addresses are generated. This thread has a great explanation: How are ethereum addresses generated? However, what this explanation is missing is why a hash is used. There ...
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11 votes
1 answer
1k views

How could msg.sender != tx.origin AND extcodesize(caller) == 0 be true?

I'm working on a puzzle where msg.sender != tx.origin, so the implication is that the caller needs to be a contract or at least something in between the calling account. But extcodesize(caller) == 0 ...
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11 votes
1 answer
2k views

Can an Ethereum address hold more than Ether?

Let me explain it with examples. On Bitcoin protocol, for example, you have Counterparty. As it uses embedded consensus, every XCP address is linked to a Bitcoin address. So if you hold bitcoins on ...
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10 votes
2 answers
1k views

Programmatically saving the contract address of a submitted contract

I understand how the below web3js code block works, adapted from here: https://github.com/ethereum/wiki/wiki/JavaScript-API#web3ethcontract But how does one save the contract address ...
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  • 235
10 votes
1 answer
14k views

What's a fallback function when using address.send(...)?

This code is in my contract: contract A { address x = 0x1234...; x.send(10); } What would fallback function in the contract at address 0x1234... look like? contract B { ... } ...
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10 votes
2 answers
4k views

How does Ethereum avoid address collision?

Recently PillarProject reported an issue where there was collision (?) of sort. Apparently their smart contract address on Rinkeby testnet matched with real address on the mainnet. I am aware that ...
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10 votes
1 answer
2k views

Why are the last 20 bytes of the public key used as the address?

According to this post regarding how to derive the Ethereum address from a public key: Take the last 40 characters / 20 bytes of this public key (Keccak-256). Or, in other words, drop the first ...
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9 votes
3 answers
7k views

Convert an eth key to a geth key

I need to convert my eth key to a geth key. eth put the key in %appdata%\roaming\Web3\keys, and I see it as a .json file. If I move that to the %appdata%\roaming\Ethereum\keystore directory, geth ...
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  • 93
9 votes
1 answer
4k views

Return Token Contract address on truffle deploy

I am trying to figure out how to return the address of a contract when I deploy it with truffle's deployer.deploy. So the goal is that when I deploy a contract that is a custom token, I want to ...
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