[fprint] About DigitalPersona U.are.U 4500

[Daniel Drake]

Jeff Yang wrote:
> I did compare the USB traces between 4000B and 4500 with 1.3.0 SDK. Like 
> I mentioned in my previous email, the driver does NOT send any 
> “firmware” data blob to 4500. It DOES send “firmware” data blob to 
> 4000B. Now I don’t know where to start to figure out how to disable 
> hardware encryption since we don’t know what’s in the “firmware” (data 
> chunk? or compiled binary code? and what the compiler is?).

For the 4000B, we did not need to understand the firmware (or even have 
a filesystem copy of it, in the end) in order to disable encryption. The 
same could possibly be true for the 4500.

> I think 
> DigitalPersona uses Windows Crypto API for the encryption. I need to do 
> more study to see if it’s possible to decrypt the image. An interesting 
> thought is how they decrypt the image under Linux? They write some 
> compatible library to simulate the windows Crypto API?

Encryption happens on the device, not on the computer. I am pretty sure 
that the DigitalPersona device does not run Windows. Therefore they do 
not use the Windows Crypto API for encryption. And even if they did, I 
don't think that says anything about the actual encryption scheme being 
used.

Daniel