In Cory Doctorow's novel "Little Brother", the passage which resonated with me the most was the one on page 57 where Marcus had just given up his phone password to Carrie Johnstone. In this passage, he begins to explain the essence of cryptography and the reason why it stood out the most was that in that one short passage, he went over almost everything that we have done in historical aspect of our cryptography class.
Firstly, he touches upon the fact that cryptography used by the common man is just as strong as the one used by the National Security Agency. This is representative of the progress we've made as compared to the cryptography used by Mary Queen of Scots, a topic we discussed in detail as the first chapter of Simon Singh's "The Code Book". In that chapter, we see how niche cryptography was and more so cryptanalysis whereas now it is a ubiquitous phenomenon, very often taken for granted.
Secondly, Marcus talks about how his privacy was in question, again something we have deliberated on as we weighed out the balance between public safety and privacy. Reading between the lines, it is also seen that when it comes to cryptography, having enough resources can always crack the code, regardless of the ethics of the means you use to do so. Just like in the San Bernardino's case, the FBI found a way to get past the encryption, the DHS were able to pressure Marcus into giving up his own privacy, which begs the question that in an absolute sense, can anything ever be kept completely secret?
Finally, Marcus asserts that the best means of measuring the efficacy of an encryption is its prevalence. This argument runs parallel to the ideas of Joseph Bramah's challenge as explained in "Perfect Security-99 Percent Invisible" where he explains the mechanism behind it and still exacts the public to try and open it. The fact that his lock was not picked for a substantial period of time reinforces the level of security it provided to its user.