[Cryptography] [cryptography] Show Crypto: prototype USB HSM

[Ron Garret]

On Apr 13, 2016, at 2:22 PM, Bill Frantz <frantz at pwpconsult.com> wrote:

> On 4/13/16 at 10:14 AM, ron at flownet.com (Ron Garret) wrote:
> 
>> Here’s a photo of an earlier version of the HSM using a seven-segment display instead of the current 128x32 pixel OLED, next to the current version for size comparison:
> 
> I normally carry a USB flash drive in my pocket. With the connector retracted, it is a bit less than 3 US nickels (2.25 inches, 58mm) long. I would have no problem with either of the pictured devices.

The prototype SC4-HSM case is 57x21x9 mm.  The USB connector extends out 14mm beyond the edge of the case.  It’s bigger than some portable USB devices, smaller than others.  It’s almost exactly the same size as e.g. the MobileMate SD+ card reader:

http://www.amazon.com/Sandisk-Mobilemate-Plus-Memory-Reader/dp/B002PX99D4/ref=pd_sim_147_5

The case is 3-D printed plastic so a production version could probably shave a couple of mm off of that.  There is also quite a bit of extra length on the board to support the debug connector that will be be taken of in the final design.

I abandoned the smaller design because the seven-segment display turned out to be inadequate for security.  4x7 segments gives you 28 bits of output at most (and realistically only 16 bits under non-geek UI constraints), and that’s not enough.

rg