by Bob Bruen, Cipher Book Review Editor
This a short book because the actual text stops at page 212, the next 65 pages are source code and an example of a grammar, so it's a quick read. It is listed as intermediate/advanced, but most of it is straight forward and clearly written. The biggest hurdles are knowing what steganography is, getting through a little bit of math (mostly Huffman encoding and RSA), and understanding Noam Chomsky's view of grammar. Enough of Chomsky's context-free grammar is presented to understand the chapter.
Steganography seems to have two main audiences, those who know about and those who don't. Of those that do know about, there are two groups, those that like it and those that feel that security through obfuscation is not a good idea. Whether it is the best or even a reasonable option is not important to me, but instead it is more important to understand the idea. The basic concept is to hide information. In today's world we think of using unimportant bits in a high resolution digital image, so that the image is not altered such that it is perceptible, but if you know that those bits have meaning, you could collect together to find the message. In the old days a message could be hidden in a secret compartment which would also be a version of steganography. Wayner uses the phrase disappearing cryptography to mean steganography.
The book has four parts to it, an introduction to the concept, a general explanation, and the third is information that is intended to help if you want to implement some of the algorithms. The fourth is the source code. Each chapter is structured the same way, with an allegorical story for the introduction followed by the general information and then the technical details, but there is no source code. The stories are cute, but not as useful the rest of the book, unless I missed the hidden messages.
The discussion of mimicry and grammars to produce written passages with hidden messages is interesting. The choices of words of particular parts of speech in a sentence represent bits, so if "Joe" is 0 and "Fred" is 1, "is" and "here" each represent 0 and "was" and "there" were 1, then "Joe is here" would be 000, "Fred is here" would be 100, etc. The grammars and code to run them can quite complex if one tries to mimic a reasonable paragraph or essay that a human would write. The challenge is to have a sentence that looks reasonable that is generated on the fly, not something simple minded like my example.
Wayner has a nice presentation of remailers that is good for anyone not familiar with them. He also gives clear explanations for Turing machines (and reversing them), white noise and basic encryption. Disappearing Cryptography is solid introduction to steganography that is both inexpensive and readable.
A real plus for the book are the sixty photographs. They are helpful to round out the discussions and some are quite unique. There is a photo of J. Edgar Hoover with the child Shirley Temple looking through a microscope accompanying more than two pages of his personal history. Another interesting photo is Allan Pinkerton with President Abraham Lincoln out in the field. The pictures of the SR-71 Blackbird and U2 in the air are striking. On the water the Liberty (hit by Israel in 1967) and the Pueblo (captured by Korea in 1968) are also interesting supplements to the description of the events that made them famous.
The spies are both real and fictional with entries for Harold Philby and James Bond. The fictional characters are listed by first name with an [F] following their name to avoid confusion. Pseudonyms are also designated with a [P]. Several authors such as Ian Fleming and John le Carre (David Cornwall) have entries since their work is mainly about espionage. The movies and literary spies are entries that cover the fictional entertainment world in the broader sense.
In the real world of spies, one finds good coverage of Mossad (Israel), MI5 and MI6 (Britain), the CIA and the FBI, German Japan, France, China, and of course China. The historical work is enhanced by current events. One has wonder about the psychic work down by the DIA (Defense Intelligence Agency) for about $20 million from the mid-80s to 1995 in project Stargate, but the Soviets and the French also thought it worth investigating. The CIA took over the project and quietly closed it down. Each of the US military branches has several organizations or groups related to espionage and communications which are well covered.
Individuals both famous and obscure are given detailed treatment. One of few known spies for Japan in the US was Velvalee Dickinson and her husband Lee. She used her doll shop in New York as a cover sending letters with code phrases to a Japanese agent with return addresses belonging to her customers. When the Japanese agent moved, the letters were properly returned the customers who could not understand what happened. Eventually Velvalee was arrested and convicted.
The Dickinson case is in the company of articles like the one covering the now famous Enigma machine. A great picture of some German soldiers trying to troubleshoot one in a field vehicle is included.
If you are unaware of the Soviet historical figures or the current Chinese status, Spy Book is a good source. This book is next to my copy of Kahn's Codebreakers as reference material worth reading.