We're going to need a way to enter this code into the BBB. This code is used to populate one of the TPM's PCRs that will be used to seal the GPG key. This keypad will be connected to the ATmega328p on the CryptoCape. While the BBB is more than capable of handling the I/O for the keypad, by using the ATmega328p, we take advantage of code reuse. For most hardware products in the SparkFun catalog, there exists at least an unofficial Arduino library. If the components aren't available at SparkFun, then you should be able to find similar parts from the product descriptions. In the case of the keypad, there is an official library. The hardware for this project is listed in the following table:

To build this Arduino library, you'll first need to install the Keypad library from the Arduino playground site: http://playground.arduino.cc/code/Keypad. Then...