Identity vs. Secrecy

Yet another story has released showing the vulnerability of facial recognition software to relatively simple countermeasures. AI company, Kneron, fooled banks, border controls, and airports with 3D printed masks designed to look like other individuals. They were able to fool security systems and automated payment vendors.

The story isn’t unique, and it’s not limited to facial recognition. We’re deep into generations of fingerprint scanners which still fail to balance between too-sensitive-to-work and recognizes-anyone-that-tries. Privacy experts will warn you, don’t use a fingerprint to lock your device. Police-watchers will warn you that you can be compelled to open a device with a fingerprint lock.

So what’s the take-away? Should we toss out biometrics? Is the premise dead on arrival? Or maybe we just need to keep developing the technology until it can defeat the next line of attack.

I will argue that the industry behind biometrics is fighting the wrong battle. At its heart, biometrics are about identity, not privacy or secrecy. This is a vital distinction, not a semantic argument. Identity is about establishing that a subject is who they claim to be. It’s a science of its own, and notoriously difficult in the digital space. Having biometrics play a role in this aspect of digital transactions is helpful. Rather than a user needing to remember a complex unique identifier, their identity is permanently etched into their body. Let the face be scanned or finger swiped! Let the system use that to infer who we are. Just, please, don’t let that be the entire process.

It has been well established that identity proofing is only part of the process. The NIST Identity Guidelines, recently updated, separates the concerns of identity proofing from authentication wisely. These are separate tasks and both necessary (as well as other aspects like federation).

Take the example of the United States social security number. This is a unique identifier given to each citizen around birth (i.e., Identity). It has no mechanism to be changed. Citizens are told to guard it from prying eyes (i.e., Secret). It is used to authenticate financial transactions and is used for government services. So when the Office of Personnel Management (OPM) was breached and leaked millions of individuals' social security numbers, that secrecy was forever lost. Without a mechanism to reset it, there is no fix.

I don’t need to cover the hundreds of other data breaches which have widened the issue over the last few years. The entire SSN system, it can be said, is effectively dead as a reliable authentication method.

So how should it work? Well, it’s not far off. Let’s take an example from Iceland’s IceKey system as a reasonable parallel to the SSN of the United States.

Every individual registered in Iceland has a unique identifier called a Kennitala. This is a number made up of the individual’s birth date and 4 control digits. It is used for everything from banking to hospital visits to utility billing. But it is not used alone. For identity purposes a Kennitala may be sufficient, but for authentication a second step is brought in.

IceKey is a system of single-signon (oAuth) which is run by Registers Iceland. It allows individuals to attach a password or passphrase to their Kennitala. In this way the identity number can be thought of as the username.

This is good. A username is an identifier. A proper secret is used to handle the authentication, and all is well with the world. IceKey has methods to safely generate a unique initial passphrase for individuals signing up, and offers delivery of that initial phrase either by mail or electronically through delivery to the individual’s bank. The password can later be changed in case it is lost.

These management aspects are important. Having a true secret is important. Biometrics cannot solve these two problems for us and shouldn’t be applied that way.

A fingerprint cannot be changed. It can easily be lost. You leave it on everything you touch, in fact. A face is worse! You post it publicly, share it on thousands of security cameras and wave it in front of friends and enemies alike. It is, by definition, not secret. It provides nothing beyond a reasonable assumption of identity, like a username. And any system that needs to reliably assure itself of that identity to complete a transaction MUST endeavor to properly authenticate that assumption with a true secret.

Biometrics represents a fantastic technological innovation in the realm of identity assumption. It cannot, and should not, be used for identity proof or authentication. It will fail. This is not a limit of technology, but a limit of philosophy.

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