YubiKeys Are a Security Gold Standard—but They Can Be Cloned

The YubiKey 5, the astir wide utilized hardware token for two-factor authentication based connected the FIDO standard, contains a cryptographic flaw that makes the finger-sized instrumentality susceptible to cloning erstwhile an attacker gains impermanent carnal entree to it, researchers said Tuesday.

The cryptographic flaw, known arsenic a side channel, resides successful a tiny microcontroller utilized successful a ample fig of different authentication devices, including smartcards utilized successful banking, physics passports, and the accessing of unafraid areas. While the researchers person confirmed each YubiKey 5 bid models tin beryllium cloned, they haven’t tested different devices utilizing the microcontroller, specified arsenic the SLE78 made by Infineon and successor microcontrollers known arsenic the Infineon Optiga Trust M and the Infineon Optiga TPM. The researchers fishy that immoderate instrumentality utilizing immoderate of these 3 microcontrollers and the Infineon cryptographic room contains the aforesaid vulnerability.

Patching Not Possible

YubiKey shaper Yubico issued an advisory successful coordination with a detailed disclosure report from NinjaLab, the information steadfast that reverse engineered the YubiKey 5 bid and devised the cloning attack. All YubiKeys moving firmware anterior to mentation 5.7—which was released successful May and replaces the Infineon cryptolibrary with a customized one—are vulnerable. Updating cardinal firmware connected the YubiKey isn’t possible. That leaves each affected YubiKeys permanently vulnerable.

“An attacker could exploit this contented arsenic portion of a blase and targeted onslaught to retrieve affected backstage keys,” the advisory confirmed. “The attacker would request carnal possession of the YubiKey, Security Key, oregon YubiHSM; cognition of the accounts they privation to target; and specialized instrumentality to execute the indispensable attack. Depending connected the usage case, the attacker whitethorn besides necessitate further knowledge, including username, PIN, relationship password, oregon authentication key.”

Side channels are the effect of clues near successful carnal manifestations specified arsenic electromagnetic emanations, information caches, oregon the clip required to implicit a task that leaks cryptographic secrets. In this case, the broadside transmission is the magnitude of clip taken during a mathematical calculation known arsenic a modular inversion. The Infineon cryptolibrary failed to instrumentality a communal side-channel defence known arsenic changeless clip arsenic it performs modular inversion operations involving the Elliptic Curve Digital Signature Algorithm. Constant clip ensures the time-sensitive cryptographic operations execute is azygous alternatively than adaptable depending connected the circumstantial keys.

More precisely, the broadside transmission is located successful the Infineon implementation of the Extended Euclidean Algorithm, a method for, among different things, computing the modular inverse. By utilizing an oscilloscope to measurement the electromagnetic radiation portion the token is authenticating itself, the researchers tin observe tiny execution clip differences that uncover a token’s ephemeral ECDSA key, besides known arsenic a nonce. Further investigation allows the researchers to extract the concealed ECDSA cardinal that underpins the full information of the token.

In Tuesday’s report, NinjaLab cofounder Thomas Roche wrote: