This chapter provided a close look at BeagleBone capes and the CryptoCape. We introduced the idea of trusted computing and built a biometric authentication system. We've shown the normal use case for I2C devices and illustrated how one rogue device can corrupt the entire bus.

In the next chapter, we'll use the BBB to protect e-mail encryption and signing keys for Pretty Good Privacy (PGP) and its free software implementation: GPG.