Cloudflare is testing a system to allow users to use FIDO keys to skip CAPTCHAs.
From a user perspective, a Cryptographic Attestation of Personhood works as follows:
1. The user accesses a website protected by Cryptographic Attestation of Personhood, such as cloudflarechallenge.com.
2. Cloudflare serves a challenge.
3. The user clicks I am human (beta) and gets prompted for a security device.
4. User decides to use a Hardware Security Key.
5. The user plugs the device into their computer or taps it to their phone for wireless signature (using NFC).
6. A cryptographic attestation is sent to Cloudflare, which allows the user in upon verification of the user presence test.
Completing this flow takes five seconds. More importantly, this challenge protects users’ privacy since the attestation is not uniquely linked to the user device. All device manufacturers trusted by Cloudflare are part of the FIDO Alliance. As such, each hardware key shares its identifier with other keys manufactured in the same batch (see Universal 2nd Factor Overview, Section 8). From Cloudflare’s perspective, your key looks like all other keys in the batch.
Cloudflare says it is primarily interested in reducing the amount of time users spend on CAPTCHAs, which it estimates currently take up 500 years of user time every day.
CAPTCHAs are certainly frustrating, and anything that can be done to replace them while still mitigating brute force and DDOS attacks is great. But it would also be great to see FIDO keys become more accepted and normalized across the Internet.
Of course after I buy a half-dozen YubiKey 4 keys, the company goes and releases the YubiKey 5 series with FIDO2/WebAuthn support. 🙂
Single-Factor Authentication (Passwordless) with the YubiKey 5 Series – The YubiKey 5 security keys can be used alone for strong single-factor authentication, requiring no username or password to login — just tap or touch to authenticate.
Second-Factor Authentication with the YubiKey 5 Series – Used alongside a username and password, the YubiKey 5 series offers a strong second factor of authentication. This is the YubiKey integration that exists today with services like Google, Twitter, and Facebook, and it is most familiar to our users.
Multi-Factor Authentication (Passwordless + PIN + Touch) with the YubiKey 5 Series – The YubiKey 5 series can be used in conjunction with a PIN for user verification. In this case, the PIN unlocks the device locally and touch is still required for the YubiKey to perform the authentication.
Really looking forward to seeing what the uptake is on the passwordless single-factor authentication turns out to be, especially as Google’s recently released hardware authentication key also supports it.
I had some concerns about physical security with the passwordless authorization, but it appears that users can add a pin to the authentication keys in that setup if desired.
In the YouTube video below, Joshua Reynolds presents at the IEEE Symposium on Security and Privacy about a couple of usability studies he and others conducted testing the usability of configuring and using Yubico’s Yubikey two-factor authentication security keys.
Two-factor authentication (2FA) significantly improves the security of password-based authentication. Recently, there has been increased interest in Universal 2nd Factor (U2F) security keys-small hardware devices that require users to press a button on the security key to authenticate. To examine the usability of security keys in non-enterprise usage, we conducted two user studies of the YubiKey, a popular line of U2F security keys. The first study tasked 31 participants with configuring a Windows, Google, and Facebook account to authenticate using a YubiKey. This study revealed problems with setup instructions and workflow including users locking themselves out of their operating system or thinking they had successfully enabled 2FA when they had not. In contrast, the second study had 25 participants use a YubiKey in their daily lives over a period of four weeks, revealing that participants generally enjoyed the experience. Conducting both a laboratory and longitudinal study yielded insights into the usability of security keys that would not have been evident from either study in isolation. Based on our analysis, we recommend standardizing the setup process, enabling verification of success, allowing shared accounts, integrating with operating systems, and preventing lockouts.