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Ethereum Address Length

Web3js - Ethereum Address String Size - Ethereum Stack Exchange

Web3js - Ethereum Address String Size - Ethereum Stack Exchange

How many (or up to how many) characters does a Ethereum address have? I have been looking online for an answer but it seemed harder to find than I expected. I am working on storing a list of Ethereum addresses with web3.js in a MySQL database, and need to know the limit of characters I should put for the VARCHAR. I could ofcourse put a very high value like 100 and be safe from not having enough space, however that would cost some speed. If you just need to store the raw address, @jeff's answer below is correct. If you're looking to store ways of referring to Ethereum accounts, you may want to ensure that your table supports things like the Ethereum name service (ENS). While ENS does map things to addresses that can be expressed using 40-character hex strings by hashing them, you may want to store the pre-hashed values which can be arbitrarily long and can be unicoded. You'll still want to put a character limit on your column, but you'll want to at least set an encoding for the column to support unicode. lungj Jul 14 '17 at 3:05 Continue reading >>

Ethereum Account 0x76bc9e61a1904b82cbf70d1fd9c0f8a120483bbb Info

Ethereum Account 0x76bc9e61a1904b82cbf70d1fd9c0f8a120483bbb Info

// /*Copyright (c) 2015-2016 Oraclize srl, Thomas BertaniPermission is hereby granted, free of charge, to any person obtaining a copyof this software and associated documentation files (the "Software"), to dealin the Software without restriction, including without limitation the rightsto use, copy, modify, merge, publish, distribute, sublicense, and/or sellcopies of the Software, and to permit persons to whom the Software isfurnished to do so, subject to the following conditions:The above copyright notice and this permission notice shall be included inall copies or substantial portions of the Software.THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS ORIMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THEAUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHERLIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS INTHE SOFTWARE.*/pragma solidity ^0.4.0;contract OraclizeI { address public cbAddress; function query(uint _timestamp, string _datasource, string _arg) payable returns (bytes32 _id); function query_withGasLimit(uint _timestamp, string _datasource, string _arg, uint _gaslimit) payable returns (bytes32 _id); function query2(uint _timestamp, string _datasource, string _arg1, string _arg2) payable returns (bytes32 _id); function query2_withGasLimit(uint _timestamp, string _datasource, string _arg1, string _arg2, uint _gaslimit) payable returns (bytes32 _id); function getPrice(string _datasource) returns (uint _dsprice); function getPrice(string _datasource, uint gaslimit) returns (uint _dsprice); function useCoupon(string _coupon); Continue reading >>

Questions On Public Addresses

Questions On Public Addresses

Private Key : 5JAyXYqnR6N123LWq64JHC74CeXrHPtNMq6xRuHvk7Aip2BrYQ3 Public Key : 1BZgEQ6sogmehQVFRJsLYmU8ZqaaQX5WKh How does it work in Ethereum? It would be nice if there was a bitaddress.org type site for Ethereum, it would at least be a step towards people understanding how addresses were calculated. Also, is the algorithm finalised yet? If I was to spend time making a vanity address right now, what's the chance that something changes in the future and my address is useless. Thanks! Continue reading >>

How Long Are Ethereum Addresses? - Ethereum

How Long Are Ethereum Addresses? - Ethereum

From An Ethereum address represents an account. For external owned accounts, the address is derived as the last 20 bytes of the public key controlling the account, e.g., cd2a3d9f938e13cd947ec05abc7fe734df8dd826. This is a hexadecimal format (base 16 notation), which is often indicated explicitly by prepending 0x to the address. Since each byte of the address is represented by 2 hex characters, a prefixed address is 42 characters long. They are 20 bytes (40 characters) excluding the 0x prefix. This is kind of a weird length. You create an address by taking the sha3 hash of your public key and cleaving off the last 20 bytes. I'm not sure why, but here is an implementation: i thought keccak uses a different padding scheme compared to sha3? SHA-3 initially refers to the target of the competition that NIST organized from 2008 to 2012, namely a new hash standard that would complement SHA-2 in case it is broken. Hence, the initially-intended outcome of the competition is a set of four functions called SHA3-224, SHA3-256, SHA3-384, and SHA3-512. It turned out that Keccak has more to offer than just the drop-in replacements for SHA-{224, 256, 384, 512}. So I believe there are other SHA3 functions that people use besides the Keccak ones. For Ethereum, you will always be using Keccak-256, which is a particular function in the superset of SHA3. If you're even unsure if your function is correct, I have found this site to be a good authority: . Also, you can compare your hash to something produced in a constant function in solidity (sha3 and keccak256 produce the same output in solidity). Continue reading >>

The Erc20 Short Address Attack Explained

The Erc20 Short Address Attack Explained

GOLEM's tech team published a nice find today -- a vulnerability for any service that takes user-generated withdrawal addresses and passes them in unaudited to a transfer function. From their post at : The service preparing the data for token transfers assumed that users will input 20-byte long addresses, but the length of the addresses was not actually checked. edit: I mistook bytes and nibbles, thanks to Noel Marsk for the careful reading! The server taking in user data allowed an Ethereum address that was less than 20 bytes: usually an Ethereum address looks like 0x1234567890123456789012345678901234567800. What if you leave off those trailing two zeros (one hex byte equal to 0)? The Ethereum VM will supply it, but at the end of the packaged function arguments, and that's a very bad place to add extra zeros. The transfer function arguments get shifted over one byte from the point that a short argument was given, and this shifts over the number of tokens transferred. Let's say I have 1,000 tokens and would like 256,000 -- what do I do? Generate an Ethereum address with a trailing 0. Ethereum addresses are generated pretty much randomly, so on average this will take 256 tries -- almost no time at all. Find an exchange wallet with 256,000 tokens. Send 1,000 tokens to this exchange wallet, crediting my account internally (off chain) with 1,000. Request a withdrawal of 1,000 tokens using my generated address. Critically I will leave off my last "0" byte. What happens then? Read the Golem blog for a clear explanation, but in brief, if the server does not validate the address, it will "pack" everything together and move the amount, the final argument, over one byte, yielding a 67 byte argument to the transfer function when 68 is what's needed. All these arguments are passed Continue reading >>

Inside An Ethereum Transaction

Inside An Ethereum Transaction

CodeTract is a startup focused on building smart contracts enforced by blockchains Ethereum can be thought of as a transaction based state machine, where transactions can change the state and the state keeps track of interactions. Here we examine at a high level, the constituents of a transaction and explain how most of the gibberish hex values are determined. We will be using nodejs in this tutorial so we start off by installing the dependencies. $ npm install [email protected] [email protected] [email protected] Then creating a file tx.js and requiring the dependencies. var web3 = new Web3(new Web3.providers.HttpProvider(' )); First we start with a private key. Ethereum uses public key cryptography for authentication. More specifically, Elliptic Curve Digital Signature Algorithm (ECDSA) with secp256k1s curve is used. The private key is just a random 256 bit data except for some restrictions . For example var privateKey = '0xc0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0dec0de'; var publicKey = util.bufferToHex(util.privateToPublic(privateKey)); and you should get the following if you print out publicKey 0x4643bb6b393ac20a6175c713175734a72517c63d6f73a3ca90a15356f2e967da03d16431441c61ac69aeabb7937d333829d9da50431ff6af38536aa262497b27 The Ethereum address associated with this private key is the last 160 bit of the SHA3256 (Keccak) hash of the public key. var address = '0x' + util.bufferToHex(util.sha3(publicKey)).slice(26); //0x53ae893e4b22d707943299a8d0c844df0e3d5557 As you can observe, it is actually possible for multiple private keys to have the same address. An Ethereum account is associated with each address and each have the following attributes nonce the count of the number of outgoing transactions, starting with 0 balance the amount of ether in the account Continue reading >>

How Are Ethereum Addresses Generated?

How Are Ethereum Addresses Generated?

What criteria does a valid ethereum address need to fulfil? Is it just a random number in hexadecimal? Or does it need to be derived in a specific way, according to some cryptographic algorithm? What algorithms and standards are used to generate the keypair? I don't agree about the duplicate. Question is not about verifying if the address is valid but rather how the address is built and if it follows a format or is just random. Indeed it's not random but the result of some processes. The fact that the word "valid" is in the question is not a criteria, you won't mark all questions with the "valid" word as duplicates ! Nicolas Massart May 3 '16 at 15:38 @tayvano I'm not the one who asked this question Nicolas Massart May 4 '16 at 5:55 It's totally fine that questions get edited/improved and voted for reopening. Here we go. 5chdn May 4 '16 at 11:51 There are three main steps to get from private -> address: Create a random private key (64 (hex) characters / 256 bits / 32 bytes) Derive the public key from this private key (128 (hex) characters / 512 bits / 64 bytes) Derive the address from this public key. (40 (hex) characters / 160 bits / 20 bytes) Even though a lot of people call the address the public key, it's actually not the case in Ethereum. There is a separate public key that acts as a middleman that you won't ever see, unless you go poking around a pre-sale wallet JSON file. The private key is 64 hexadecimal characters. Every single string of 64 hex are, hypothetically, an Ethereum private key (see link at top for why this isn't totally accurate) that will access an account. If you plan on generating a new account, you should be sure these are seeded with a proper RNG. Once you have that string.. This is hard and beyond me. There is something with Elliptic Curve Di Continue reading >>

Ethereum Address Validator: Tool To Validate Eth Addresses?

Ethereum Address Validator: Tool To Validate Eth Addresses?

Ethereum is an open source, unrestricted, blockchain based distributing computer platform that features scripting (smart contract) functionality. The platform provides a decentralized virtual machine known as the EVM (Ethereum virtual machine). This machine has the capability to execute scripts using public nodes spread all over the globe. Ethereum has also provided a cryptocurrency that is referred to as Ether. The currency can be transferred from one account to another and can be used in compensating all participating nodes for the computations they perform. There is an internal transaction mechanism used to determine the pricing referred to as Gas, and its used primarily in spam mitigation. It also assists in allocating resources throughout the network. The Process of Checking an Ethereum Address The Ethereum Address Validator is a tool that is used in validating Ethereum addresses. The validator is designed for use in cases where payers need to verify whether a transaction receiver has correctly communicated his or her address. It was designed to prevent scenarios where a payment is sent to an unrecoverable or mistyped Ethereum address. Benefits of the Ethereum Address Validator It is backward compatible with common hex parsers, especially those that accept mixed case letters. This allows it to be slowly introduced as time goes by. Ethereum Address Validator ensures that characters do not surpass the 40 length limit The address checksum has been encoded in lower and upper case variation of A-F hexadecimal letters that are contained in an address. This means that if the typed address only includes lowercase letters, it will not be possible to establish whether that particular address is valid or not. When this happens, you will need to request the address sender to Continue reading >>

Speculators Jump On New Gold Rush Called Ethereum Name Service

Speculators Jump On New Gold Rush Called Ethereum Name Service

Speculators Jump On New Gold Rush Called Ethereum Name Service ENS allows anyone to create a simple and memorable Ether address. Many speculators are jumping on board this new gold rush. Ethereum Name Service (ENS) launched on mainnet on May 4, 2017. At launch, ENS featured an automated registrar process allowing anyone to easily and cheaply register names ending in ".eth" using an auction process. The auction system enabled anyone to purchase a .eth addresses of at least seven characters in length. Since its launch over 618,000 auctions have been started, and 3,298,707 ETH have been deposited for bids. The ENS is evolving, and within the next two years, a planned upgrade will allow for auctions of shorter names less than seven characters. The Ethereum Name Service brings readable Ether addresses to the public. This is a key step towards cryptocurrency mass adoption . Normal Ether addresses are 42 digits long and can be very confusing for beginners. ENS enables anyone to create a much more user friendly address like for example JohnDoe.eth. Since many Ethereum names are being purchased at ENS auction, new owners of .eth names have been seeking efficient tools enabling them to transfer ownership of their newly acquired .eth names to second hand purchasers. As some Ethereum names are very valuable, an escrow service for transfer of title to these names has been important, but no such service has existed. Buyers and sellers seeking to transfer ownership have been required to rely on trust, custom smart contracts, or legal contracts provided by attorneys. Over the past six months since the launch of the ENS, individual .eth names have auctioned for astronomical sums. Some of the more expensive .eth names have included exchange.eth claimed for 6,660 ETH ($609,000), foundati Continue reading >>

Types Solidity 0.2.0 Documentation

Types Solidity 0.2.0 Documentation

to the type. The default for function parameters (including return parameters) is There is also a third data location, calldata, which is a non-modifyablenon-persistent area where function arguments are stored. Function parameters(not return parameters) of external functions are forced to calldata andit behaves mostly like memory. Data locations are important because they change how assignments behave:Assignments between storage and memory and also to a state variable (even from other state variables)always create an independent copy.Assignments to local storage variables only assign a reference though, andthis reference always points to the state variable even if the latter is changedin the meantime.On the other hand, assignments from a memory stored reference type to anothermemory-stored reference type does not create a copy. contract c { uint[] x; // the data location of x is storage // the data location of memoryArray is memory function f(uint[] memoryArray) { x = memoryArray; // works, copies the whole array to storage var y = x; // works, assigns a pointer, data location of y is storage y[7]; // fine, returns the 8th element y.length = 2; // fine, modifies x through y delete x; // fine, clears the array, also modifies y // The following does not work; it would need to create a new temporary / // unnamed array in storage, but storage is "statically" allocated: // y = memoryArray; // This does not work either, since it would "reset" the pointer, but there // is no sensible location it could point to. // delete y; g(x); // calls g, handing over a reference to x h(x); // calls h and creates an independent, temporary copy in memory } function g(uint[] storage storageArray) internal {} function h(uint[] memoryArray) {}} contract C { function f() returns (uint[]) { ... Continue reading >>

How To Find Out If An Ethereum Address Is A Contract?

How To Find Out If An Ethereum Address Is A Contract?

An address in Solidity can be an account or a contract (or other things, such as a transaction). When I have a variable x, holding an address, how can I test if it is a contract or not? (Yes, I've read the chapter on types in the doc) Edit: Solidity has changed since this answer was first written, @manuel-aroz has the correct answer. There is no way in solidity to check if an address is a contract. One of the goals of Ethereum is for humans and smart contracts to both be treated equally. This leads into a future where smart contracts interact seamlessly with humans and other contracts. It might change in the future , but for now an arbitrary address is ambiguous. Yes you can, by using some EVM assembly code to get the address' code size: function isContract(address addr) returns (bool) { uint size; assembly { size := extcodesize(addr) } return size > 0;} This isn't something you can query from within a contract using Solidity, but if you were just wanting to know whether an address holds contract code or not, you can check using your geth console or similar with eg: > eth.getCode("0xbfb2e296d9cf3e593e79981235aed29ab9984c0f") with the hex string (here 0xbfb2e296d9cf3e593e79981235aed29ab9984c0f) as the address you wish to query. This will return the bytecode stored at that address. You can also use a blockchain scanner to find the source code of the contract at that address, for example the ecsol library as shown on etherscan.io . Continue reading >>

Understanding Private Key, Public Key & Address In Ethereum Blockchain

Understanding Private Key, Public Key & Address In Ethereum Blockchain

Public key is described as follows in yellow paper . Where pu is the public key, assumed to be a byte array of size 64 (formed from the concatenation of two positive integers each < 2256) and pr is the private key, a byte array of size 32 (or a single positive integer in the aforementioned range). This is done using group operation of EC cryptography. To derive public key, private key is multiplied by G.Multiplication used to derive public is EC multiplication which is entirely different from normal multiplication for which I am going to use JS library . G is called generator point which is one of the domain parameters of EC cryptography. G has fixed value for ecp256k1, which is recommended by experts. you can read more here . var EC = require('elliptic').ec;var BN = require('bn.js');var ec = new EC('secp256k1');var G = ec.g; // Generator pointvar pk = new BN('1'); // private key as big numbervar pubPoint=G.mul(pk); // EC multiplication to determine public point var x = pubPoint.getX().toBuffer(); //32 bit x co-ordinate of public point var y = pubPoint.getY().toBuffer(); //32 bit y co-ordinate of public point var publicKey =Buffer.concat([x,y])console.log("pub key::"+publicKey.toString('hex')) Ethereum address is described as follows in yellow paper For a given private key, pr, the Ethereum address A(pr) (a 160-bit value) to which it corresponds is defined as the right most 160-bits of the Keccak hash of the corresponding ECDSA public key. To generate Ethereum address, take Keccak-256 hash of public key. Right most 20 bytes is your Ethereum address. var EC = require('elliptic').ec;var BN = require('bn.js');var ec = new EC('secp256k1');const keccak256 = require('js-sha3').keccak256;var privateKey=Buffer.alloc(32, 0);privateKey[31]=1;console.log("PK::"+privateKey.toStrin Continue reading >>

Accounts, Addresses, Public And Private Keys, And Tokens

Accounts, Addresses, Public And Private Keys, And Tokens

Accounts, Addresses, Public And Private Keys, And Tokens The format of your private key is 3a1076bf45ab87712ad64ccb3b10217737f7faacbf2872e88fdd9a537d8fe266. The format of your account (which is generated from your public key) is 0xC2D7CF95645D33006175B78989035C7c9061d3F9. Note that there is a lowercase version 0xc2d7cf95645d33006175b78989035c7c9061d3f9 and a partially uppercase version 0xC2D7CF95645D33006175B78989035C7c9061d3F9. The partially uppercase version has a checksum to verify the address. See EIP55 - Yet another cool checksum address encoding The password encrypted private key is stored in a JSON file with the following format (newlines and indents added for clarity, example on OS/X): $ more ~/Library/Ethereum/keystore/UTC--2017-03-18T05-48-53.504714737Z--c2d7cf95645d33006175b78989035c7c9061d3f9 {"address":"c2d7cf95645d33006175b78989035c7c9061d3f9", "crypto":{ "cipher":"aes-128-ctr", "ciphertext":"0f6d343b2a34fe571639235fc16250823c6fe3bc30525d98c41dfdf21a97aedb", "cipherparams":{ "iv":"cabce7fb34e4881870a2419b93f6c796" }, "kdf":"scrypt", "kdfparams"{ "dklen":32, "n":262144, "p":1, "r":8, "salt":"1af9c4a44cf45fe6fb03dcc126fa56cb0f9e81463683dd6493fb4dc76edddd51" }, "mac":"5cf4012fffd1fbe41b122386122350c3825a709619224961a16e908c2a366aa6" }, "id":"eddd71dd-7ad6-4cd3-bc1a-11022f7db76c", "version":3} How To Create New Accounts (or Addresses) How To Create A New Account In Go Ethereum (geth) You can generate a new Ethereum account by executing geth account new if you already have the geth Ethereum node software installed: $ geth account newYour new account is locked with a password. Please give a password. Do not forget this password.Passphrase: xxxxxxxxRepeat passphrase: xxxxxxxxAddress: {4e6cf0ed2d8bbf1fbbc9f2a100602ceba4bf1319} A UTC--{year}-{month}--{account} enc Continue reading >>

Introduction Ens 0.1 Documentation

Introduction Ens 0.1 Documentation

ENS is the Ethereum Name Service, a distributed, open, and extensible naming system based on the Ethereum blockchain. ENS can be used to resolve a wide variety of resources. The initial standard for ENS defines resolution for Ethereum addresses, but the system is extensible by design, allowing more resource types to be resolved in future without the core components of ENS requiring upgrades. The primary goal of ENS is to resolve human-readable names, like myname.eth, into machine-readable identifiers, including Ethereum addresses, Swarm and IPFS content hashes, and other identifiers. A secondary purpose is to provide metadata about names, such as ABIs for contracts, and whois information for users. ENS has similar goals to DNS, the Internets Domain Name Service, but has significantly different architecture, due to the capabilities and constraints provided by the Ethereum blockchain. Like DNS, ENS operates on a system of dot-separated hierarchial names called domains, with the owner of a domain having full control over the distribution of subdomains. Top-level domains, like .eth and .test are owned by smart contracts called registrars, which specify rules governing the allocation of their subdomains. Anyone may, by following the rules imposed by these registrar contracts, obtain ownership of a second-level domain for their own use. ENS has two principal components: the registry, and resolvers. The ENS registry consists of a single central contract that maintains a list of all domains and subdomains, and stores three critical pieces of information about each: The time-to-live for all records under the domain The owner of a domain may be either an external account (a user) or a smart contract. A registrar is simply a smart contract that owns a domain, and issues subdomain Continue reading >>

Address Length Is Supposed To Be 40 Characters For `--peerset` - Why? #109

Address Length Is Supposed To Be 40 Characters For `--peerset` - Why? #109

The length of enode addresses is 128 chars, but is required to be 40 in code. That is, unless, my understanding of the format of peerset is incorrect, and it requires something other than enode. My command: eth --peerset required:38ce9dca995a05b20c8aacbc2dd1112e09e1813f585071209337ed0d0ec52ea64[email protected]127.0.0.1:30303 --listen 30305 Continue reading >>

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