Blog Post 23

Data.php

<?php
namespace MageVision\Blog23\Helper;

use Magento\Framework\App\Helper\AbstractHelper;
use Magento\Framework\Encryption\EncryptorInterface;

class Data extends AbstractHelper
{
    const XML_PATH_PASSWORD = 'blog/post23/password';

    /**
     * @var EncryptorInterface
     */
    protected $encryptor;

    /**
     * @param EncryptorInterface $encryptor
     */
    public function __construct(
        EncryptorInterface $encryptor
    ) {
        $this->encryptor = $encryptor;
    }

    /**
     * Get Password from config
     *
     * @return string
     */
    public function getPassword()
    {
        $password = $this->scopeConfig->getValue(self::XML_PATH_PASSWORD, \Magento\Store\Model\ScopeInterface::SCOPE_STORE);
        return $this->encryptor->decrypt($password);
    }
}

system.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <tab id="magevision" translate="label" sortOrder="1000">
            <label>MageVision Blog Posts</label>
        </tab>
        <section id="blog" translate="label" type="text" sortOrder="1009" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Blog Post 23</label>
            <tab>magevision</tab>
            <resource>MageVision_Blog23::blog23_configuration</resource>
            <group id="post23" translate="label" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>General</label>
                <field id="password" translate="label" sortOrder="10" type="obscure" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Password</label>
                    <backend_model>Magento\Config\Model\Config\Backend\Encrypted</backend_model>
                </field>
            </group>
        </section>
    </system>
</config>