From a security perspective perhaps it's not that interesting-- although signing oracles are all too common access to one is already close enough to a total break even before getting to the padding restriction. (e.g. go ahead and sign post dated certificates too).
But the technique is interesting as an object of study, in a way that finding "beginner-levle crypto misuse" absolutely wouldn't be, so it makes it more relevant as an academic publication. It further clarifies just how fragile these constructs are.
Also from a security perspective I suspect this may be a total break on some blind signature token schemes that use RSA. I've seen some of those avoid using ECC on the basis of the complexity required to avoid one-more-signature attacks that require making a fair number of concurrent blind signatures. (and have a shape a lot like this attack!)
> How do you fix a "vulnerability" that doesn't exist?
Don't make a signing oracle (esp one that doesn't even do the padding itself) available!
For the last bit see my longish reply above. PKCS #11 when the vendor doesn't bother locking down their API, which the one in the paper didn't, gives you a whole string of ways to pull keys out of HSMs, which is why you put your HSM behind as many layers of access control as you can manage. Either that or buy an HSM which the vendor has locked down so attacks like the one in the paper just bounce off.
But really, never expose your HSM to outside access because for most of them the keys will be extractable one way or another.
But the technique is interesting as an object of study, in a way that finding "beginner-levle crypto misuse" absolutely wouldn't be, so it makes it more relevant as an academic publication. It further clarifies just how fragile these constructs are.
Also from a security perspective I suspect this may be a total break on some blind signature token schemes that use RSA. I've seen some of those avoid using ECC on the basis of the complexity required to avoid one-more-signature attacks that require making a fair number of concurrent blind signatures. (and have a shape a lot like this attack!)
> How do you fix a "vulnerability" that doesn't exist?
Don't make a signing oracle (esp one that doesn't even do the padding itself) available!