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How easy is it for somebody to get your PGP key off a yubikey if they stole it? In particular since physical devices can be fuzzed, etc, it might be worse than
by Torgo 11y ago
How easy is it for somebody to get your PGP key off a yubikey if they stole it? In particular since physical devices can be fuzzed, etc, it might be worse than an encrypted keychain on device for some people?
- w8rbt 11y agoI don't know how difficult it would be to obtain the key from the device. However, if you have a strong passphrase on the key itself, then even if an attacker obtained the key, there would not be a lot to worry about. Just revoke it and move on. They'll likely never guess the passphrase.
- e12e 11y agoIf you're that confident in your pass-phrase, you could just push your private key to github. Might want to consider that there is some overlap between being able to steal your yubi-key, and being able to install a hardware (or software) key logger...
- mrsteveman1 11y agoThe passphrase you set on a GPG private key only applies to keys stored on-disk in the keychain or exported from the keychain. Once you import one into a Yubikey or other OpenPGPCard device, there is no passphrase anymore, you're relying on the card itself to protect it against side-channel attacks, prevent unauthorized or insecure export of the key (Yubikeys don't allow this at all though), and authorize the use of it via the PIN code.
- w8rbt 11y agoThanks for that explanation. I've never placed any of my GPG keys on a Yubikey. I just assumed that the key password remained.
- JuliaLang 11y agoAfter three pin attempts, the key is wiped.
- mrsteveman1 11y agoThe Yubikey NEO used the NXP a700x microcontroller family the last I checked (NEO-n might as well but I'm not sure). You can read about the security features of the chip at NXP's website[1] to get a sense for what they're designed to defend against, but despite the very real possibility of a successful key retrieval attack on the card, in general it would be MUCH easier for an attacker to obtain your on-disk keychain files and figure out the password. Particularly if they don't want you to be aware the key has been compromised. [1] http://www.nxp.com/products/identification_and_security/authentication/series/A700X_FAMILY.html http://www.nxp.com/products/identification_and_security/auth...
- AlyssaRowan 11y agoSmart cards/hardware tokens try to not make themselves easy targets, and many such microcontrollers have attempts (of varying success) to defend against limited degrees of physical access and make attacks evident. But in any case, given sufficient time and resources, the attacker will always win. Bottom line: It depends largely on who stole it and for how long - however, if someone knew enough to target stealing your hardware token/smart card, you are under targeted attack and your key's probably toast: revoke it. I would also gently caution that the elliptic curve routines provided by NXP should not be used over special prime fields (elliptic curves that are fast in software, i.e. just about everything except Brainpool) as they abuse the large (RSA) multiplier whose side-channel blinding was not designed for non-random fields. (Unless they've rewritten it since I last saw it?)