Extending a PCR

We'll need to extend a PCR so that we can encrypt our GPG key. We'll arbitrarily choose PCR number 9. First let's view the PCR status to be sure that it is blank:

cat /sys/class/misc/tpm0/device/pcrs | grep PCR-09

This should return the current state of the PCR, which without using secure boot is:

PCR-09:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Now, run the getgpgpin program from the following section. You should see the LED turn green on the CryptoCape and you have 10 seconds to enter a five-digit pin. Each time you press a key, the LED should briefly flash and when five digits have been entered, the LED will turn off. After 10 seconds, the getgpgpin program will silently exit. If you compiled the program with #define DEBUG set to 1, you should see something like this:

54321
(Line 53, extend_pcr)  Create a Context
 returned 0x00000000. Success.
(Line 55, extend_pcr)  Connect to TPM
 returned 0x00000000. Success.
(Line 59, extend_pcr)  GetTPM...