In addition to biometric authentication, Windows Hello supports authentication with a PIN. By default, Windows requires a PIN to consist of four digits, but can be configured to permit more complex PINs. However, a PIN is not a simpler password. While passwords are transmitted to domain controllers, PINs are not. They are tied to one device, and if compromised, only one device is affected. Backed by a Trusted Platform Module (TPM) chip, Windows uses PINs to create strong asymmetric key pairs. As such, the authentication token transmitted to the server is harder to crack. In addition, whereas weak passwords may be broken via rainbow tables, TPM causes the much-simpler Windows PINs to be resilient to brute-force attacks.
On the general availability build of Windows 10 (the original release), to activate and generate the \"digital entitlement\" for Windows 10, the operating system must have first been installed as an in-place upgrade. During the free upgrade, a genuineticket.xml file is created in the background and the system's motherboard details are registered with a Microsoft Product Activation server. Once installed, the operating system can be reinstalled on that particular system via normal means without a product key, and the system's license will automatically be detected via online activation - in essence, the Microsoft Product Activation Server will remember the system's motherboard and give it the green light for product re-activation. Because of installation issues with Upgrade Only installs, the November Update (version 1511) included additional activation mechanisms. This build treated Windows 7 and Windows 8/8.1 product keys as Windows 10 product keys, meaning they could be entered during installation to activate the free license, without the need to upgrade first to \"activate\" the hardware with Microsoft's activation servers. For major Original Equipment Manufacturers (OEMs), Windows 8/8.1 and Windows 10 OEM product keys are embedded in the firmware of the motherboard and if the correct edition of Windows 10 is present on the installation media, they are automatically inputted during installation. Since the release of the Fall Creators Update (version 1709), Microsoft decided to release multi-edition installation media, to alleviate installation and product activation issues users experienced because of accidentally installing the wrong edition of Windows 10.
During upgrades, Windows 10 licenses are not tied directly to a product key. Instead, the license status of the system's current installation of Windows is migrated, and a \"Digital license\" (known as \"Digital entitlement\" in version 1511 or earlier) is generated during the activation process, which is bound to the hardware information collected during the process. If Windows 10 is reinstalled cleanly and there have not been any significant hardware changes since installation (such as a motherboard change), the online activation process will automatically recognize the system's digital entitlement if no product key is entered during installations. However, unique product keys are still distributed within retail copies of Windows 10. As with previous non-volume-licensed variants of Windows, significant hardware changes will invalidate the digital entitlement, and require Windows to be re-activated. 076b4e4f54