In Little Brother, the main character Marcus Yarrow repeatedly uses cryptography to spread information without the DHS's knowledge while disguising it in the chaos of data. Though the characters are only teenagers, they certainly have moved past childish cryptography methods such as caesar ciphers or even vigenére ciphers.
To spread secret messages, the characters need an unbreakable cipher and a way to hide their communication. Instead of creating their own enciphering method, they use public keys that everyone can access. Though this seems counterintuitive, the method of using public keys is actually much safer than the best cipher someone could create on their own. Public keys have been tested and tried, while a secret key can either be discovered by a spy or cracked if weak enciphering methods are used. With public keys, you are more certain your cipher hasn't been compromised because everyone else would be compromised too. If you try to hide your key, you have no idea as to the strength of the key because no one has ever tried to crack it yet. The "so public it's private" double layering of information seems as though it would be easy to spot, but as Little Brother shows, the amount of data humans now have to process means it is becoming easier and easier to simply blend in with the noise.
Throughout the novel, instead of looking suspicious, the characters try to either make their patterns look as normal as possible or create so many false positives that odd behavior becomes ordinary. This disguising of information combined with a public, computer encrypted cipher system allowed the characters to easily pass along information without getting the attention of the DHS.
Though this seemingly contradictory approach to secrecy may seem unique to this novel, it has become the standard practice in the world today. Before and during WWII, secrecy of keys was of primary importance, but they were still either discovered or cracked. Today, the rise of computers has made it almost impossible to send messages the old way because computers can do thousands more calculations to decipher almost anything. By using tested public and private key combinations and by disguising the true message within the flood of data, as in Little Brother, messages can be easily sent and received without being compromised or even detected.