Finding additional background information
The projects in the book are, for the most part, self-contained. However, they do assume that you have some background knowledge in working with a GNU/Linux system, electronics, and some cryptographic concepts. The following sections list some resources in each area for those who want to seek further information.
Finding additional cryptography resources
The projects in this book all use some sort of cryptography. If you are familiar with terms such as asymmetric cryptography, digital signatures, and message authentication codes, then you should be OK. If not, you will still be able to complete the projects but you may not appreciate the theory behind them.
As this is not a book on cryptography, a primer here will not provide enough detail for a beginner and will be woefully inadequate for someone familiar with the material. If cryptography is new to you, you can still proceed with the book. In the beginning of each chapter, there is some tailored background to explain the material, which should be enough for you to understand what the project is trying to accomplish. Once complete, hopefully, you'll be interested in cryptography and you can get more information from the following resources.
For a gentle introduction to the topic, Cryptography: A Very Short Introduction by Fred Piper and Sean Murphy, Oxford University Press, 2002, is good starting point. However, as the title suggests, it lacks technical depth. Understanding Cryptography: A Textbook for Students and Practitioners by Christof Paar et. al., Springer, 2010, is a more detailed introduction. For the more inquisitive readers, Introduction to Modern Cryptography by Jonathan Katz and Yehuda Lindell, Chapman and Hall/CRC, 2007, is a good up-to-date reference.
If lectures better suit you, you are in luck. Khan Academy has some interesting and free mini-lectures covering ancient cryptography up to RSA (https://www.khanacademy.org/computing/computer-science/cryptography). Another free resource is Coursera, which has three cryptography classes, Cryptography I and II taught by Standford Professor Dan Boneh, and a Cryptography class on modern cryptography taught by Jonathan Katz. The links for these classes are https://www.coursera.org/course/crypto, https://www.coursera.org/course/crypto2, and https://www.coursera.org/course/cryptography, respectively.
Finding additional electronics resources
Similarly, this book assumes some basic electronics knowledge. If you are looking for a book, Practical Electronics for Inventors, Third Edition by Paul Scherz and Simon Monk, Tab Books, 2013, is a solid and approachable reference. Khan Academy has a series on basic concepts in electricity and magnetism as well (https://www.khanacademy.org/science/physics/electricity-and-magnetism). Dave Jones EEVBlog is an entertaining and informative video blog that covers many areas of electronics and should be of interest to hobbyists in electronics (http://www.eevblog.com/).
Finding additional Debian resources
For those new to Debian, there is an comprehensive and free handbook available online called The Debian Administrator's Handbook by Raphaël Hertzog and Roland Mas, Freexian SARL, 2014, at http://debian-handbook.info/browse/stable/. At a minimum, you should read Chapter 6, Maintenance and Updates: The APT Tools, of this book, which details how to use the apt set of tools for package management. There is also a free class offered by the Linux Foundation and edX called Introduction to Linux (https://www.edx.org/course/linuxfoundationx/linuxfoundationx-lfs101x-introduction-1621). The class is fairly recent and it does not appear to use the Debian distribution, but it does seem like a representative course on generic Linux information. Lastly, there are several Debian IRC channels on the OFTC IRC network. Most of the channels start with #debian and you should be able to ask specific questions there. The BeagleBoard channel is #beagle on Freenode, and there will be people there who can help answer your questions as well.
