Why trust gpg4win?

[Jan]

On 10/9/2013 14:19, Werner Koch wrote :
>However, [USB] is implemented by computers at boths ends and the software
>there may have backdoors or explotable code which coult be used for all
>kind of tricks [...]

I am shocked! Why was USB constructed that insecure?!

On 10/9/2013 14:19, Werner Koch wrote :
>So what about using that free USB stack for AVR's to implement a flash
>device?  You would be able to audit about everything; flylogic even has
>these nice pictures of the ATmega88 masks...

I don't understand this, what does AVR etc. mean? Is there a substituion for 
USB? I'd be grateful for an explanation.

Kind regards,
Jan