6 ms·

At least in my mind, the defining attribute of an HSM is protection against physical compromise of the device. Maybe we disagree on that definition: I guess it

At least in my mind, the defining attribute of an HSM is protection against physical compromise of the device. Maybe we disagree on that definition: I guess it is hardware, and it exists for security, and it's a module. I admit it's unfair to compare this with a $10,000 HSM from Thales or Safenet, of course. But it seems like a smartcard based solution might be better on that front, as they're designed to withstand physical attacks. You can defend against some side channels (timing from the host, for example) but I was thinking more like EM/RF emissions. I want to be clear that I think this is still a great project, and I commend your work so far!

lisper 10y ago
> smartcard Those are not at all secure against compromised hosts. > EM/RF emissions You probably don't want to use this to secure the nuclear launch codes. But I think you'd have to work pretty damn hard to get anything out of it. There are no external parts here, it's all one SoC, one that is specifically designed to keep proprietary code out of the hands of Chinese hackers. If it were easy to attack it would lose most of its market. > I commend your work so far! Thanks!
- mSparks 10y ago
  just thinking out loud. definately not disagreeing with your hardware choice. a good idea for a pi zero?
  - lisper 10y ago
    You could certainly do something like this with a pi. But it would be bulkier and probably less secure. But my initial prototyping was done with a Teensy3. It all depends on your threat model.
    - mSparks 10y ago
      its great that we are getting access to so many tiny sweet tiny boards. just in case - pi zero: https://www.raspberrypi.org/products/pi-zero/ https://www.raspberrypi.org/products/pi-zero/ i was thinking more feature set than threat model. Namely Secure at rest storage and password generator for secure comms. i believe the pi has a hwrnd which is probably the most essential thing for such devices.
- amluto 10y ago
  >> smartcard > Those are not at all secure against compromised hosts. How so? Certainly there are poorly designed applications on smartcards that are vulnerable, but the smartcard itself should be fine.
  - lisper 10y ago
    If an attacker pwns your host they can do anything you can do. If you can access the smartcard, then the attacker can too. As soon as you plug the card in, the card is just as compromised as the host. This is the reason that the SC4-HSM has a built-in display and user inputs. These serve the same purpose as the display on a PoS terminal, except that because they are a part of the HSM itself, they can't be compromised by an attacker who pwns the host that the HSM is plugged in to. An attacker can still attempt a phishing attack, but this will be much, much harder. And for really mission-critical applications, an attacker would have to control every possible means of computing a secure hash on the host machine. I should probably write a paper about this.
    - Karunamon 10y ago
      I thought that the whole point of a smartcard is that your keys, once loaded, can never be extracted again, even by the host. Rather than passing secrets to the host directly, there's a miniature PKI that does request/signature, secured by a password, using a hardware pinpad if you're very serious. Little window for error too, since screwing up the password some small number of times results in the card being blocked, and in some cases, destroyed. Even if the host is running hostile code, the worst it could do is forge signing requests?
      - lisper 10y ago
        > screwing up the password If the host machine is pwned then it's not hard to steal your password. > the worst it could do is forge signing requests Well yeah, that's true. But if the card is protecting a really sensitive asset (like your bitcoin account) then a single forged request can do an awful lot of damage.
brians 10y ago
We disagree on that definition. The defining attribute of an HSM is protection against software compromise of the main computer. Having provided near-perfect defense against a software-only adversary, many HSM vendors then add layers and layers of protection for the hardware. But the real key is ensuring that someone who gets root on your server can use your keys but not copy them.
zimmerfrei 10y ago
>> At least in my mind, the defining attribute of an HSM is protection against physical compromise of the device. FIPS definitions help a bit here. A hardware FIPS 140 Level 2 cryptographic module (HSM) is only required to show evidence of tampering. A $5 broken seal if often the solution. Note that applying a seal to the module in the link is not sufficient because I can compromise the thing without opening it (just press the button and reflash with non-signed images). Level 3 is a step up in that you must have some degree of tamper resistance, but in several cases, most of this security behemoths just drop a layer of epoxy on the board and call it a day. Then they sell it to you for $10.000. With Level 4 things get serious, but then you can count your suppliers in on hand and pay accordingly (and Safenet is not one of them). I agree that smartcard-based solution would be ideal, but specs and native firmware and SDK are never open, so you cannot build an open-source product with them.
- serendipitous 10y ago
  > because I can compromise the thing without opening it (just press the button and reflash with non-signed images). I don't think so. With RDP enabled the only thing the bootloader lets you do is erase all flash. After that RDP is disabled and you can write your own image but at that point the keys are already gone.

lisper 10y ago

> smartcard Those are not at all secure against compromised hosts. > EM/RF emissions You probably don't want to use this to secure the nuclear launch codes. But I think you'd have to work pretty damn hard to get anything out of it. There are no external parts here, it's all one SoC, one that is specifically designed to keep proprietary code out of the hands of Chinese hackers. If it were easy to attack it would lose most of its market. > I commend your work so far! Thanks!

mSparks 10y ago
just thinking out loud. definately not disagreeing with your hardware choice. a good idea for a pi zero?
- lisper 10y ago
  You could certainly do something like this with a pi. But it would be bulkier and probably less secure. But my initial prototyping was done with a Teensy3. It all depends on your threat model.
  - mSparks 10y ago
    its great that we are getting access to so many tiny sweet tiny boards. just in case - pi zero: https://www.raspberrypi.org/products/pi-zero/ https://www.raspberrypi.org/products/pi-zero/ i was thinking more feature set than threat model. Namely Secure at rest storage and password generator for secure comms. i believe the pi has a hwrnd which is probably the most essential thing for such devices.
amluto 10y ago
>> smartcard > Those are not at all secure against compromised hosts. How so? Certainly there are poorly designed applications on smartcards that are vulnerable, but the smartcard itself should be fine.
- lisper 10y ago
  If an attacker pwns your host they can do anything you can do. If you can access the smartcard, then the attacker can too. As soon as you plug the card in, the card is just as compromised as the host. This is the reason that the SC4-HSM has a built-in display and user inputs. These serve the same purpose as the display on a PoS terminal, except that because they are a part of the HSM itself, they can't be compromised by an attacker who pwns the host that the HSM is plugged in to. An attacker can still attempt a phishing attack, but this will be much, much harder. And for really mission-critical applications, an attacker would have to control every possible means of computing a secure hash on the host machine. I should probably write a paper about this.
  - Karunamon 10y ago
    I thought that the whole point of a smartcard is that your keys, once loaded, can never be extracted again, even by the host. Rather than passing secrets to the host directly, there's a miniature PKI that does request/signature, secured by a password, using a hardware pinpad if you're very serious. Little window for error too, since screwing up the password some small number of times results in the card being blocked, and in some cases, destroyed. Even if the host is running hostile code, the worst it could do is forge signing requests?
    - lisper 10y ago
      > screwing up the password If the host machine is pwned then it's not hard to steal your password. > the worst it could do is forge signing requests Well yeah, that's true. But if the card is protecting a really sensitive asset (like your bitcoin account) then a single forged request can do an awful lot of damage.

brians 10y ago

We disagree on that definition. The defining attribute of an HSM is protection against software compromise of the main computer. Having provided near-perfect defense against a software-only adversary, many HSM vendors then add layers and layers of protection for the hardware. But the real key is ensuring that someone who gets root on your server can use your keys but not copy them.

zimmerfrei 10y ago

>> At least in my mind, the defining attribute of an HSM is protection against physical compromise of the device. FIPS definitions help a bit here. A hardware FIPS 140 Level 2 cryptographic module (HSM) is only required to show evidence of tampering. A $5 broken seal if often the solution. Note that applying a seal to the module in the link is not sufficient because I can compromise the thing without opening it (just press the button and reflash with non-signed images). Level 3 is a step up in that you must have some degree of tamper resistance, but in several cases, most of this security behemoths just drop a layer of epoxy on the board and call it a day. Then they sell it to you for $10.000. With Level 4 things get serious, but then you can count your suppliers in on hand and pay accordingly (and Safenet is not one of them). I agree that smartcard-based solution would be ideal, but specs and native firmware and SDK are never open, so you cannot build an open-source product with them.

serendipitous 10y ago
> because I can compromise the thing without opening it (just press the button and reflash with non-signed images). I don't think so. With RDP enabled the only thing the bootloader lets you do is erase all flash. After that RDP is disabled and you can write your own image but at that point the keys are already gone.