We have decided to halt development of new features related to the original Signet's firmware to focus on stabilizing and freezing the firmware. Significant new features such as FIDO U2F that we had previously hoped to implement take up too much flash storage space to implement without drastically shrinking the personal information database. We will still fix bugs and work on client-level enhancements for Signet however.
The Signet HC can support new features such file encryption and SSH authtenication (via a GPG integration), FIDO2 U2F, and mass storage support for both encrypted and unencrypted volumes. These features are made possible thanks to its much larger microcontroller flash storage capacity, much faster processor, 32 GB of eMMC flash, and the presence of a cryptographic accelerator. See the campaign page page and read the campaign updates for more information.
Another of Signet HC's major improvements is that it does not tend to disconnect during button presses the way some of the original Signets tended to when the contacts became dirty. This improvement is due to a combination of a better USB connector and a better voltage regulator to make the power signal robust.