Encrypt/Decrypt String using a Private Secret Key with PHP

In this tutorial, we are going to learn how to encrypt and decrypt a message using a private secret key with PHP.

<h1 style="text-align: center;">Encrypt/Decrypt String using a Private Secret Key with PHP</h1>



<?php


  function encrypt($message, $encryption_key){
    $key = hex2bin($encryption_key);

    $nonceSize = openssl_cipher_iv_length('aes-256-ctr');
    $nonce = openssl_random_pseudo_bytes($nonceSize);

    $ciphertext = openssl_encrypt(
      $message, 
      'aes-256-ctr', 
      $key,
      OPENSSL_RAW_DATA,
      $nonce
    );
    return base64_encode($nonce.$ciphertext);
  }

  function decrypt($message,$encryption_key){
    $key = hex2bin($encryption_key);
    $message = base64_decode($message);
    $nonceSize = openssl_cipher_iv_length('aes-256-ctr');
    $nonce = mb_substr($message, 0, $nonceSize, '8bit');
    $ciphertext = mb_substr($message, $nonceSize, null, '8bit');

    $plaintext= openssl_decrypt(
      $ciphertext, 
      'aes-256-ctr', 
      $key,
      OPENSSL_RAW_DATA,
      $nonce
    );
    return $plaintext;
  }

  $original_string = "Lets Try This";
  $private_secret_key = '1f4276388ad3214c873428dbef42243f' ; //some random hex characters


  $encrypted = encrypt($original_string,$private_secret_key);
  echo '<h3>Original String : '.$original_string.'</h3>';
  echo '<h3>After Encryption : '.$encrypted.'</h3>';
  echo '<h3>After Decryption : '.decrypt($encrypted,$private_secret_key).'</h3>';