[Opensc-devel] Nitrokey HSM - Details of DKEK/key-wrapping algorithm, or key import

[Evan A. <EAn...@we...>]

I recently acquired a Nitrokey HSM for testing for one of my Customers. The 
feature-set of the SmartCard-HSM software appears to be quite good and a 
nearly perfect fit for my Customer's needs.

My Customer will be signing firmware for a series of embedded control 
devices w/ RSA keys. These devices have a planned 15-20 year lifetime in the 
field/market (embedded devices attached to very large, very expensive pieces 
of machinery with long service lifetimes). Losing access to the firmware 
signing key during the device's supported lifetime would be quite bad 
(physically recalling the devices and replacing secure SoC devices w/ public 
keys stored in on-chip fuse-protected bootloader flash).

While the built-in key backup/restore functionality in SmartCard-HSM looks 
quite good, I'm concerned that without details of the 
key-wrapping/unwrapping algorithm my Customer could find themselves, in the 
future, in a situation where SmartCard-HSM is no longer available for 
purchase. I am reticent to simply recommend assuming that the Customer 
purchase extra devices to hold in storage and hope that they will remain 
functional for 10+ years. My Customer is already accustomed to supporting 
devices in the field w/ 15+ year lifetimes, so this concern is a very real 
one to them.

Are there details of the DKEK key-wrapping/unwrapping algorithm available 
(under NDA and/or for a fee, if necessary) that would enable my Customer to 
have confidence that, even if the SmartCard-HSM product were discontinued 
and no longer available, they would be able to bring the DKEK shares and 
key-backup together to reconstruct their key to load into some new device?

As an alternative to understanding the DKEK key-wrapping/unwrapping 
algorithm, is there functionality to import an externally-generated key into 
the SmartCard-HSM product? I see a reference here 
<http://www.smartcard-hsm.com/features.html#keyimport> but I've reviewed all 
the materials I can find publicly, and on the CardContact Developer Network 
website, and I am not finding any examples or documentation showing how to 
perform this import. On this mailing list, as recently as October 2015 
(under the thread "Cannot delete imported private key from SmartCard-HSM") I 
am seeing statements that make me think that this import functionality may 
have difficulties.

Thank you,
Evan Anderson
Wellbury LLC
Troy, OH, US