Windows 10 will let you log in to your PC, tablet, phone, or even website with nothing more than your finger or face by using a pair of new features called Windows Hello and codename "Passport."

Windows Hello is a new integrated biometric system for passwordless authentication on Windows devices. Windows 10 users will be able to log in using their faces, their fingerprints—already common on many laptops—or their eyeballs, using iris recognition. The system will support automatic sign-in simply by sitting in front of the PC, Kinect-style.

The goal is to obviate the need for passwords, which continue to be a weak link in computer security. Weak passwords and passwords shared across multiple systems continue to expose people and sites to attack, and biometrics are increasingly being promoted as the solution to this problem.

The same infrastructure for passwordless logins will also be available to third-party developers using a new framework that Microsoft has codenamed Passport. This will open up the same system of biometric logins to applications, networks, and perhaps most importantly of all, websites.

Microsoft announced in February that it was joining the Fast IDentity Online (FIDO) Alliance. FIDO's specifications provide a standard way for sites to support biometric, passwordless authentication. The same authentication hardware that will be usable with Hello will also be usable with FIDO.

One of the sensitivities around biometric systems is the storage of biometric data. In common with other systems such as Apple's Touch ID, Hello and Passport store all biometric data locally on the system, never transmitting it across the network. The biometric authentication is handled entirely on the PC. It's used to unlock cryptographic data that is then used for securely logging in to remote sites using the well-known principles of asymmetric cryptography.

As with so many Windows features, Windows Hello and Passport are both dependent on having appropriate hardware. Face and iris recognition will need special cameras that have only started to show up on shipping systems; they require infrared illumination and detection to ensure that they can't be trivially faked out using photographs. The Intel RealSense 3D Camera, found on a handful of new PCs, is the first hardware on the market that has this support. Conventional webcams won't do the job.

While fingerprint readers are more common, they're still typically found on enterprise-oriented machines rather than consumer ones. And presently, not a single Windows Phone ships with a fingerprint reader, even though Windows 10 on phones will also support Hello and Passport. Wider availability of this hardware will be invaluable in improving password security, and it appears that Windows 10 will be providing the necessary software support to make this technology mainstream. We just hope that the OEMs do their part and build biometric devices into more systems.