5 ms·

Whoever cloned the hardware would need to know the private key Yubico embed in it, and those aren't east to extract, although presumably feasible for cutting ed

Whoever cloned the hardware would need to know the private key Yubico embed in it, and those aren't east to extract, although presumably feasible for cutting edge chip reverse engineering labs.

amelius 5y ago
Or whoever manufactured the Yubico chip in the first place.
- GekkePrutser 5y ago
  That's infineon for the latest generation: http://www.hexview.com/~scl/neo5/ http://www.hexview.com/~scl/neo5/
- yjftsjthsd-h 5y ago
  I wonder if you could mitigate that by manufacturing them without a private key and then have Yubico themselves program the keys (in one-time programmable memory) before shipping to the customer.
cromd 5y ago
Here's an example from 2018 of someone trying to extract secrets from a Yubikey. https://duo.com/labs/research/microcontroller-firmware-recovery-using-invasive-analysis https://duo.com/labs/research/microcontroller-firmware-recov.... Seems they don't get very far. Or it's at least very laborious. But as you say, who knows what a cutting edge lab can do. Skimming the web, it seems like people have had more success with things like Google Titan keys.
- GekkePrutser 5y ago
  That's not a yubikey but a standard pic microcontroller not designed for security applications. And as far as I understand he's now describing his methods there rather than particular attempts?
  - drdaeman 5y ago
    There's a bit about Yubikey at the very end of the article.
- jsmith99 5y ago
  If you are interested in this topic, the physical security chapter of Ross Anderson's Security Engineering has a nice intro. The second edition is free online https://www.cl.cam.ac.uk/~rja14/book.html https://www.cl.cam.ac.uk/~rja14/book.html
Nextgrid 5y ago
Out of curiosity, why are keys not generated upon first run? Why is there something to extract out of a brand new YubiKey to begin with?
- tialaramex 5y ago
  For FIDO, which was the main topic of the original post, the Yubikey has a symmetric key inside it. Choosing a random new key invalidates all your existing credentials enrolled with that Yubikey, since your Yubikey will no longer be able to decrypt the identifier provided and sign proof that it knows the associated private key (in practice what it decrypted was your private key for that account, and now it can't do that) This "reset" operation is supported on Yubikeys, and you perhaps should do it when you get the key (Don't do it now! It invalidates your credentials as I described!), although most users probably don't. However, even if you do this if your key is fake why would the initialisation actually work? The same adversary could modify it to just ignore this reset attempt and use a symmetric key they know. So there is no benefit from hypothetically requiring you to perform this initialisation step, nor from having the device do it when first used.
- deleted 5y ago
  [deleted]
tialaramex 5y ago
To do FIDO the Yubikey has a symmetric (typically called "secret" but here it isn't really functioning as a secret since nobody else knows what it is) key but not a private key baked inside it. Hiding such symmetric keys (typically AES) from adversaries with fairly large budgets who have physical access to your device is already a thing. Would I bet my life on it if I was Edward Snowden? Maybe not. Am I comfortable with this for securing a bank account with my life savings in it? Yes.

Whoever cloned the hardware would need to know the private key Yubico embed in it, and those aren't east to extract, although presumably feasible for cutting edge chip reverse engineering labs.

amelius 5y ago

Or whoever manufactured the Yubico chip in the first place.

GekkePrutser 5y ago
That's infineon for the latest generation: http://www.hexview.com/~scl/neo5/ http://www.hexview.com/~scl/neo5/
yjftsjthsd-h 5y ago
I wonder if you could mitigate that by manufacturing them without a private key and then have Yubico themselves program the keys (in one-time programmable memory) before shipping to the customer.

cromd 5y ago

Here's an example from 2018 of someone trying to extract secrets from a Yubikey. https://duo.com/labs/research/microcontroller-firmware-recovery-using-invasive-analysis https://duo.com/labs/research/microcontroller-firmware-recov.... Seems they don't get very far. Or it's at least very laborious. But as you say, who knows what a cutting edge lab can do. Skimming the web, it seems like people have had more success with things like Google Titan keys.

GekkePrutser 5y ago
That's not a yubikey but a standard pic microcontroller not designed for security applications. And as far as I understand he's now describing his methods there rather than particular attempts?
- drdaeman 5y ago
  There's a bit about Yubikey at the very end of the article.
jsmith99 5y ago
If you are interested in this topic, the physical security chapter of Ross Anderson's Security Engineering has a nice intro. The second edition is free online https://www.cl.cam.ac.uk/~rja14/book.html https://www.cl.cam.ac.uk/~rja14/book.html

Nextgrid 5y ago

Out of curiosity, why are keys not generated upon first run? Why is there something to extract out of a brand new YubiKey to begin with?

tialaramex 5y ago
For FIDO, which was the main topic of the original post, the Yubikey has a symmetric key inside it. Choosing a random new key invalidates all your existing credentials enrolled with that Yubikey, since your Yubikey will no longer be able to decrypt the identifier provided and sign proof that it knows the associated private key (in practice what it decrypted was your private key for that account, and now it can't do that) This "reset" operation is supported on Yubikeys, and you perhaps should do it when you get the key (Don't do it now! It invalidates your credentials as I described!), although most users probably don't. However, even if you do this if your key is fake why would the initialisation actually work? The same adversary could modify it to just ignore this reset attempt and use a symmetric key they know. So there is no benefit from hypothetically requiring you to perform this initialisation step, nor from having the device do it when first used.
deleted 5y ago
[deleted]

tialaramex 5y ago

To do FIDO the Yubikey has a symmetric (typically called "secret" but here it isn't really functioning as a secret since nobody else knows what it is) key but not a private key baked inside it. Hiding such symmetric keys (typically AES) from adversaries with fairly large budgets who have physical access to your device is already a thing. Would I bet my life on it if I was Edward Snowden? Maybe not. Am I comfortable with this for securing a bank account with my life savings in it? Yes.