YubiKey
The YubiKey is a hardware authentication device manufactured by Yubico that supports one-time passwords, public-key cryptography and authentication, and the Universal 2nd Factor and FIDO2 protocols developed by the FIDO Alliance. It allows users to securely log into their accounts by emitting one-time passwords or using a FIDO-based public/private key pair generated by the device. YubiKey also allows for storing static passwords for use at sites that do not support one-time passwords. Facebook uses YubiKey for employee credentials, and Google supports it for both employees and users. Some password managers support YubiKey. Yubico also manufactures the Security Key, a device similar to the YubiKey, but focused on public-key authentication.
The Yubikey implements the HMAC-based One-time Password Algorithm and the Time-based One-time Password Algorithm, and identifies itself as a keyboard that delivers the one-time password over the USB HID protocol. The YubiKey NEO and YubiKey 4 include protocols such as OpenPGP card using 1024, 2048, 3072 and 4096-bit RSA and elliptic curve cryptography p256 and p384, Near Field Communication, and FIDO U2F. The YubiKey allows users to sign, encrypt and decrypt messages without exposing the private keys to the outside world. The 4th generation YubiKey launched on November 16, 2015. It has support for OpenPGP with 4096-bit RSA keys, and PKCS#11 support for PIV smart cards, a feature that allows for code signing of Docker images.
Founded in 2007 by CEO Stina Ehrensvärd, Yubico is a private company with offices in Palo Alto, Seattle, and Stockholm. Yubico CTO, Jakob Ehrensvärd, is the lead author of the original strong authentication specification that became known as Universal 2nd Factor.
Yubikey released the Yubikey 5 series in 2018 which adds support for FIDO2.
History
Yubico was founded in 2007 and began offering a Pilot Box for developers in November of that year. The original YubiKey product was shown at the annual RSA Conference in April 2008, and a more robust YubiKey II model was launched in 2009.YubiKey II and later models have two "slots" available, for storing two distinct configurations with separate AES secrets and other settings. When authenticating the first slot is used by only briefly pressing the button on the device, while the second slot gets used when holding the button for 2 to 5 seconds.
In 2010, Yubico began offering the YubiKey OATH and YubiKey RFID models. The YubiKey OATH added the ability to generate 6- and 8-character one-time passwords using protocols from the Initiative for Open Authentication, in addition to the 32-character passwords used by Yubico's own OTP authentication scheme. The Yubikey RFID model included the OATH capability plus also included a MIFARE Classic 1k radio-frequency identification chip, though that was a separate device within the package that could not be configured with the normal Yubico software over a USB connection.
Yubico announced the YubiKey Nano in February 2012, a miniaturized version of the standard YubiKey which was designed so it would fit almost entirely inside a USB port and only expose a small touch pad for the button. Most later models of the YubiKey have also been available in both standard and "nano" sizes.
2012 also saw the introduction of the YubiKey Neo, which improved upon the previous YubiKey RFID product by implementing near-field communication technology and integrating it with the USB side of the device. The YubiKey Neo are able to transmit one-time passwords to NFC readers as part of a configurable URL contained in a NFC Data Exchange Format message. The Neo is also able to communicate using the CCID smart-card protocol in addition to USB HID keyboard emulation. The CCID mode is used for PIV smart card and OpenPGP support, while USB HID is used for the one-time password authentication schemes.
In 2014, the YubiKey Neo was updated with FIDO Universal 2nd Factor support. Later that year, Yubico released the FIDO U2F Security Key, which specifically included U2F support but none of the other one-time password, static password, smart card, or NFC features of previous YubiKeys. At launch, it was correspondingly sold at a lower price point of just $18, compared to $25 for the YubiKey Standard, and $50 for the YubiKey Neo. Some of the pre-release devices issued by Google during FIDO/U2F development reported themselves as "Yubico WinUSB Gnubby ".
In April 2015, the company launched the YubiKey Edge in both standard and nano form factors. This slotted in between the Neo and FIDO U2F products feature-wise, as it was designed to handle OTP and U2F authentication, but did not include smart card or NFC support.
The YubiKey 4 family of devices was first launched in November 2015, with USB-A models in both standard and nano sizes. The YubiKey 4 includes most features of the YubiKey Neo, including increasing the allowed OpenPGP key size to 4096 bits, but dropped the NFC capability of the Neo.
At CES 2017, Yubico announced an expansion of the YubiKey 4 series to support a new USB-C design. The YubiKey 4C was released on February 13, 2017. On Android OS over the USB-C connection, only the one-time password feature is supported by the Android OS and YubiKey, with other features not currently supported including Universal 2nd Factor. A 4C Nano version became available in September 2017.
In April 2018, the company brought out the Security Key by Yubico, their first device to implement the new FIDO2 authentication protocols, WebAuthn and Client to Authenticator Protocol. At launch, the device is only available in the "standard" form factor with a USB-A connector. Like the previous FIDO U2F Security Key, it is blue in color and uses a key icon on its button. It is distinguished by a number "2" etched into the plastic between the button and the keyring hole. It is also less expensive than the YubiKey Neo and YubiKey 4 models, costing $20 per unit at launch because it lacks the OTP and smart card features of those previous devices, though it retains FIDO U2F capability.
ModHex
When being used for one-time passwords and stored static passwords, the YubiKey emits characters using a modified hexadecimal alphabet which is intended to be as independent of system keyboard settings as possible. This alphabet, referred to as ModHex or Modified Hexadecimal, consists of the characters "cbdefghijklnrtuv", corresponding to the hexadecimal digits "0123456789abcdef". Due to YubiKeys using raw keyboard scan codes in USB HID mode, there can be problems when using the devices on computers that are set up with different keyboard layouts, such as Dvorak. It is recommended to either use operating system features to temporarily switch to a standard US keyboard layout when using one-time passwords, although YubiKey Neo and later devices can be configured with alternate scan codes to match layouts that aren't compatible with the ModHex character set.U2F authentication in YubiKeys and Security Keys bypasses this problem by using the alternate U2FHID protocol, which sends and receives raw binary messages instead of keyboard scan codes. CCID mode acts as a smart card reader, which does not use HID protocols at all.
Security issues
YubiKey 4 closed-sourcing concerns
In an example of security through obscurity, Yubico replaced all open-source components in YubiKey 4 with closed-source code, which can no longer be independently reviewed for security flaws. Yubikey NEOs still use open-source code.On May 16, 2016, Yubico CTO Jakob Ehrensvärd responded to the open-source community's concerns with a blog post saying that "we, as a product company, have taken a clear stand against implementations based on off-the-shelf components and further believe that something like a commercial-grade AVR or ARM controller is unfit to be used in a security product."
Techdirt founder Mike Masnick strongly criticized this decision, saying "Encryption is tricky. There are almost always vulnerabilities and bugs -- a point we've been making a lot lately. But the best way to fix those tends to be getting as many knowledgeable eyes on the code as possible. And that's not possible when it's closed source."
These decisions involved the use of highly specialized silicon that comes from only a few sources, whose firmware is designed using manufacturer-provided emulators. Both the specialized silicon itself, and the emulators and other tools required to program it, are invariably covered by non disclosure agreements by their suppliers and unavailable to the public or other non-recognized customers.
Accordingly, the keys contain firmware that even an end user cannot read. Further, if the firmware could be read, the end user would still lack access to the supplier's emulators and other tools required to change or validate it using a toolchain. They could also not rewrite an existing or modified firmware to their key nor obtain blank silicon to program "from clean", to test it in situ.