Ethereum Address

Ethereum addresses are composed of the prefix "0x", a common identifier for hexadecimal, concatenated with the rightmost 20 bytes of the Keccak-256 hash (big endian) of the ECDSA public key (the curve used is the so-called secp256k1, the same as Bitcoin)

There are 2 types of account in ETH network, externally owned account (EOA) and contract account. Remember account just simply mean an address.

Externally owned account (EOA)

Controlled by private key.
Has ETH balance state

Contract account

No private key, controlled by codes written in contract.
Has ETH balance state
Has associated code and state of variables declared in contract.
Learn more about Smart Contract.

<?php 
use kornrunner\Keccak;
use BitWasp\Bitcoin\Key\Factory\PrivateKeyFactory;
use BitWasp\Bitcoin\Crypto\Random\Random;

include_once "../libraries/vendor/autoload.php";
include_once("html_iframe_header.php");

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    try {
       
        $privKeyFactory = new PrivateKeyFactory();

        if (!$_POST['input'] OR ctype_xdigit($_POST['input'])) 
        {
            if (!$_POST['input']) 
            { 
                $rbg = new Random();
                $privateKey = $privKeyFactory->generateUncompressed($rbg);
                
            } else {
                
                $privateKey = $privKeyFactory->fromHexUncompressed($_POST['input']);
            }
        } 
       
		$publicKey = $privateKey->getPublicKey();
		$madeUpEthAddress = substr($publicKey->getHex(), 2);
		
		$hash = Keccak::hash(hex2bin($madeUpEthAddress), 256);
		// Ethereum address has 20 bytes length. (40 hex characters long)
		// We only need the last 20 bytes as Ethereum address
		$ethAddress = '0x' . substr($hash, -40);
		
    ?>
        <div class="table-responsive">
            <table border=0 class='table'>
                <tr style='background-color:#f0f0f0'><td>Address</td><td><?php echo $ethAddress?></td></tr>
                <tr><td>Private Key Hex</td><td><?php echo $privateKey->getHex()?></td></tr>               
                <tr style='background-color:#f0f0f0'><td>Public Key Hex</td><td><?php echo $publicKey->getHex()?></td></tr>
            </table>
        </div>
<?php 
    } catch (Exception $e) {
        $errmsg .= "Problem found. " . $e->getMessage();

    }
} 

if ($errmsg) {
?>
    <div class="alert alert-danger">
        <strong>Error!</strong> <?php echo $errmsg?>
    </div>
<?php
}
?>
<form action='' method='post'>
    <div class="form-group">
        <label for="input">Private Key (Hex):</label>
        <input class="form-control" type='text' name='input' id='input' value='<?php echo $_POST['input']?>'>
        <small>Put empty if you want system assign you a random private key.</small>
    </div>
   
    <input type='submit' class="btn btn-success btn-block"/>
</form>
<?php
include_once("html_iframe_footer.php");

Contract Address Generator

Contract address will be auto generated (without private key) when contract-type tx publish to ETH network.

Visual
Coding

<?php 
use kornrunner\Keccak;
use Web3p\RLP\RLP;

include_once "../libraries/vendor/autoload.php";
include_once("html_iframe_header.php");

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    try {
       
        $rlp = new RLP;
		$normalizedAddress = "0x" . ltrim($_POST['address'], "0x");
		
		$encoded = $rlp->encode([$normalizedAddress, (int)$_POST['nonce']]);
		$hash = Keccak::hash(hex2bin($encoded->toString('hex')), 256);
		$ethAddress = '0x' . substr($hash, -40);
		
    ?>
        <div class="table-responsive">
            <table border=0 class='table'>
                <tr style='background-color:#f0f0f0'><td>Address</td><td><?php echo $ethAddress?></td></tr>
            </table>
        </div>
<?php 
    } catch (Exception $e) {
        $errmsg .= "Problem found. " . $e->getMessage();

    }
} 

if ($errmsg) {
?>
    <div class="alert alert-danger">
        <strong>Error!</strong> <?php echo $errmsg?>
    </div>
<?php
}
?>
<form action='' method='post'>
    <div class="form-group">
        <label for="address">Sender Address:</label>
        <input class="form-control" type='text' name='address' id='address' value='<?php echo $_POST['address']?>'>
    </div>
	
	<div class="form-group">
        <label for="nonce">Nonce:</label>
        <input class="form-control" type='text' name='nonce' id='nonce' value='<?php echo $_POST['nonce']?>'>
    </div>
   
    <input type='submit' class="btn btn-success btn-block"/>
</form>
<?php
include_once("html_iframe_footer.php");

How To Determine Address Type?

You can call JSON-RPC with getcode method. if the address is representing an EOA you will get 0x as response otherwise you will get the contract's bytecode.

Visual
Coding

<?php 

include_once "../libraries/vendor/autoload.php";
$supportChains = ['1'=>"Ethereum Mainnet", '3'=>"Ethereum Testnet Ropsten"];

include_once("html_iframe_header.php");
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
	try {
		
		if (!preg_match('/^https\:\/\/([a-z]+)\.infura\.io/', $_POST['url'])) {
			throw new Exception("Please provide valid INFURA full URL with project ID.");
		}
		
		$ch = curl_init();
		
		$params = [];
		$params['jsonrpc']= "2.0";
		$params['method'] = 'eth_getCode';
		$params['params'] = [$_POST['address'],'latest'];
		$params['id'] = $_POST['chain'];
	
		curl_setopt($ch, CURLOPT_URL,$_POST['url']);
		curl_setopt($ch, CURLOPT_POST, 1);
		curl_setopt($ch, CURLOPT_POSTFIELDS,$req = json_encode($params));
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($ch, CURLOPT_HTTPHEADER, ["Content-Type: application/json"]);

		$resp = curl_exec($ch);
		
		if ($resp === false) {
			throw new Exception("curl_exec return false");
		}
		
		if (strlen($err = @curl_error($ch)) > 0) {
			$errno = @curl_errno($ch);
			throw new Exception( "{$err} ({$errno})" );
		}
		
		$result = json_decode($resp,true); 
		$result = $result['result'];
		
		curl_close ($ch);
		
		?>
		<div class="alert alert-success">
			<h6 class="mt-3">Request</h6>
			<textarea class="form-control" rows="5" id="comment" readonly><?php echo $req;?></textarea>
			<h6 class="mt-3">Response</h6>
			<textarea class="form-control" rows="1" id="comment" readonly><?php echo $resp;?></textarea>
			<h6 class="mt-3">Result</h6>
			<?php
			
			if ($result == '0x' or $result == '0x0') {
				echo "{$_POST['address']} is EOA address.";
			} else if (substr($result,0,2) == '0x' AND strlen($result) >= 3) {
				echo "{$_POST['address']} is contract address.";
			}
			?>
		</div>
		<?php
	} catch (Exception $e) {
		$errmsg .= "Problem found. " . $e->getMessage();
	}
} 

if ($errmsg) {
?>
    <div class="alert alert-danger">
        <strong>Error!</strong> <?php echo $errmsg?>
    </div>
<?php
}

?>
<form id='this_form' action='?action=submit' method='post'>

	<div class="form-group">
		<label for="chain">Chain:</label>
		<select id="chain" name="chain" class="form-control" >
			<?php
			foreach($supportChains as $k=>$v) {
				echo "<option value='{$k}'".($k == $_POST['chain'] ? " selected": "").">{$v}</option>";
			}
			?>
		</select>
	</div>
	
	 <div class="form-group">
        <label for="url">INFURA full URL (with project ID):</label>
        <input class="form-control" type='text' name='url' id='url' value='<?php echo $_POST['url']?>'>
		<small>e.g https://mainnet.infura.io/v3/11223344556677889900aabbccdd</small>
    </div>
	
	<div class="form-group">
        <label for="address">Address:</label>
        <input class="form-control" type='text' name='address' id='address' value='<?php echo $_POST['address']?>'>
    </div>
		
    <input type='submit' class="btn btn-success btn-block"/>
</form>
<?php
include_once("html_iframe_footer.php");

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