When you want to create a new field for input any password in system configuration Magento 2 but you don't want it to show the password as a text.

Here we will guide you on how to create a password type field in the admin configuration in Magento 2.

We use the “obscure” field type and 

Magento\Config\Model\Config\Backend\Encrypted as the backend_model

In the file <Module_Name>/etc/system.xml add a new field as below:

<field id='magenest_password' translate='label' type='obscure' sortOrder='3' showInDefault='1' showInWebsite='1' showInStore='1'>
   <label>Password</label>   <backend_model>Magento\Config\Model\Config\Backend\Encrypted</backend_model>
</field>

After create in System configuration will show this field for input password as image:

This field for input password

You can see that in configuration at the admin panel with the name Password. When you put or type some value then it will convert the value into a password with dot sign.

In short, when creating a field in the back-end, developers need to create an encrypted field for it for security purpose.

READ MORE. How to encrypt and decrypt data in Magento 2 - Magenest Blog

Happy coding!