[Cryptography] [Crypto-practicum] Announcement: the SC4-HSM is now a FIDO U2F token

[Ron Garret]

On Oct 17, 2016, at 7:22 AM, Pavol Rusnak <stick at gk2.sk> wrote:

> On 17/10/16 04:28, grarpamp wrote:
>> Both of these processes should be enhanced to support bitcoin.
> 
> You might want to check https://trezor.io/ for Bitcoin HW token. Uses
> same hardware, has bigger display, is open-source. Also it supports U2F
> and GPG.

I don’t think this is what grarpamp was referring to, rather s/he was talking about accepting bitcoin to buy an SC4-HSM, and offering to pay bitcoin for code review and development.

I am familiar with the Trezor, and it is indeed very similar to the SC4-HSM, but with one very important difference: the Trezor does not give you access to DFU mode on the SoC, so you can’t actually re-flash the device, nor can you inspect the contents of the flash.  Yes, you can upload new firmware, but this is done through a bootloader that permanently installed on the device, and which is not user-inspectable.  The security of the Trezor is thus not verifiable by the user.  You have to trust Satoshi Labs.

The SC4-HSM is designed to be 100% open and auditable, at least in terms of the software.  You don’t have to trust me.  You can build *all* of the firmware and the tool chain from source, and you can access DFU mode so you have direct hardware-level access to the flash.  You still have to trust me that the chip on the board is indeed an STM32F405 (you can remove the display and see the markings on the chip) and you have to trust ST Micro to have not built a back-door into that chip, but that’s a much higher bar than trusting Satoshi Labs to not have a weakness, either intentional or otherwise, in their bootloader.

rg