5 min read

Overview

PHP is very popular in developing the backend of websites or web applications. PHP has a huge crowd of developers trusting it as their go-to language. In this guide, we will see how we can generate a new Ethereum address in PHP.

Prerequisites

• PHP 7.0 or above installed with gmp extension.
• Composer installed
• A text editor
• CLI

What is an Ethereum address?

While signing in to any platform on the internet, you need to authenticate using a combination of credentials. Consider an Ethereum address as your username and a corresponding private key as the password. While your Ethereum address is public and can be shared, the private key must always be kept secret. Using this combination lets you interact with the Ethereum blockchain. An Ethereum address is your identity on the blockchain, and it looks like this “0x6E0d01A76C3Cf4288372a29124A26D4353EE51BE”. Having a valid Ethereum address is required for:

• Receiving/Sending Ethereum currency
• Signing/Sending transactions
• Connecting to decentralized applications

How an Ethereum address is generated:

A random private key of 64 (hex) characters (256 bits / 32 bytes) is generated first. For example:

0xf4a2b939592564feb35ab10a8e04f6f2fe0943579fb3c9c33505298978b74893

A 128 (hex) character (64 bytes) public key is then derived from the generated private key using Elliptic Curve Digital Signature Algorithm (ECDSA). For example:

0x04345f1a86ebf24a6dbeff80f6a2a574d46efaa3ad3988de94aa68b695f09db9ddca37439f99548da0a1fe4acf4721a945a599a5d789c18a06b20349e803fdbbe

The Keccak-256 hash function is then applied to (128 characters / 64 bytes) the public key to obtain a 64 character (32 bytes) hash string. The last 40 characters / 20 bytes of this string prefixed with 0x become the final Ethereum address. For example:

0xd5e099c71b797516c10ed0f0d895f429c2781142

Note: 0x in coding indicates that the number/string is written in hex.

What is PHP?

PHP is a recursive acronym for Hypertext Preprocessor; PHP is a widely used open-source server-side scripting language usually embedded in HTML. It is used to manage databases, session tracking, dynamic content; It works with almost all the popular databases like MySQL, PostgreSQL, MS SQL Server, etc. It has C language-like syntax and supports significant protocols like LDAP, IMAP, and POP3. PHP4 added support for Java and distributed object architectures (COM and CORBA), making n-tier development possible for the first time.

Everyday use cases of PHP

• To set and access cookie variables.
• To gather information from web forms.
• To perform system functions like opening and closing files.
• To add, delete, and modify elements in databases.
• Adding user-based restrictions on webpages.

Following are some characteristics of PHP

• Scalability
• Flexibility
• Simplicity
• Case Sensitive
• Loosely typed
• Interpreted
• Open Source

Installing PHP and other dependencies

Before installing the dependencies, which we require to generate an address, let’s check if we have PHP installed on our system. To do so, copy-paste and run the following in your terminal/cmd.

$ php -v

It should return the PHP version; if not installed, download the operating system-specific PHP following the instructions on the official PHP website’s download page.

We’ll need to install the PHP gmp extension; you can either uncomment it from the php.init file or install it manually using the following.

$ sudo apt-get install php-gmp

Note: We should enable gmp using only one of the methods mentioned above. 

For mac:

Reinstalling PHP with brew can help to enable the gmp extension, type the following commands:

$ brew reinstall php@7.2

$ export PATH="/usr/local/opt/php@7.2/bin:$PATH"

$ brew services restart php@7.2

$ php -info | grep "GMP"

We’ll use composer (A dependency manager for PHP) to manage PHP libraries/dependencies required to generate addresses and keys. Check if the composer is installed on your system or not by running the following in your terminal/cmd:

If not installed, download and install it by following the Composer website’s downloads page.

Now create a JSON file named composer.json in your project directory and copy-paste the following in it.

{
    "require": {
        "sop/asn1": "^3.3",
        "sop/crypto-encoding": "^0.2.0",
        "sop/crypto-types": "^0.2.1",
        "kornrunner/keccak": "^1.0",
        "symfony/dotenv": "^4.0",
        "sc0vu/web3.php": "dev-master"
    }
}

Save the file and install the dependencies using composer:

$ composer install

This will install the required dependencies in the directory.

Generating an Ethereum address in PHP

Now make a new PHP file named Address.php in the directory and copy-paste the following in it.

<?

require_once "vendor/autoload.";

use Sop\CryptoTypes\Asymmetric\EC\ECPublicKey;
use Sop\CryptoTypes\Asymmetric\EC\ECPrivateKey;
use Sop\CryptoEncoding\PEM;
use kornrunner\Keccak;

$config = [
    'private_key_type' => OPENSSL_KEYTYPE_EC,
    'curve_name' => 'secp256k1'
];

$res = openssl_pkey_new($config);

if (!$res) {
    echo 'ERROR: Fail to generate private key. -> ' . openssl_error_string();
    exit;
}

openssl_pkey_export($res, $priv_key);

$key_detail = openssl_pkey_get_details($res);
$pub_key = $key_detail["key"];

$priv_pem = PEM::fromString($priv_key);

$ec_priv_key = ECPrivateKey::fromPEM($priv_pem);

$ec_priv_seq = $ec_priv_key->toASN1();

$priv_key_hex = bin2hex($ec_priv_seq->at(1)->asOctetString()->string());
$priv_key_len = strlen($priv_key_hex) / 2;
$pub_key_hex = bin2hex($ec_priv_seq->at(3)->asTagged()->asExplicit()->asBitString()->string());
$pub_key_len = strlen($pub_key_hex) / 2;

$pub_key_hex_2 = substr($pub_key_hex, 2);
$pub_key_len_2 = strlen($pub_key_hex_2) / 2;

$hash = Keccak::hash(hex2bin($pub_key_hex_2), 256);

$wallet_address = '0x' . substr($hash, -40);
$wallet_private_key = '0x' . $priv_key_hex;

echo "\r\n   SAVE BUT DO NOT SHARE THIS (Private Key): " . $wallet_private_key;
echo "\r\n   Address: " . $wallet_address . " \n";
?>

Explanation of the code above

Line 1: Starting the PHP script with PHP opening tag.

Line 3-8: Importing the installed dependencies.

Line 10-20: Using secp256k1 curve to generate the private key.

Line 22: Generating the private key.

Line 24-25: Getting the public key.

Line 29-31: Converting key to Elliptic Curve Private Key Format then converting it to ASN1 Structure.

Line 33-36: Getting Private and public key in hex format.

Line 38-39: Deriving the Ethereum Address from the public key, every public key always starts with 0x04,

removing the leading 0x04 to hash it correctly.

Line 41: Getting the address in hash format.

Line 43: Adding 0x prefix and getting last 40 characters of the address hash and storing it in wallet_address variable.

Line 44: Adding 0x prefix to the private key and storing it in wallet_private_key variable.

Line 46: Printing the private key with a warning.

Line 47: Printing the Ethereum address with the string “Address:”

Now save the file and run the script.

$ php Address.php

If everything works as planned, it should look like this.

Conclusion

Congratulations on generating your very own Ethereum address in PHP; you can use this to make fantastic decentralized wallets.

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