In this slim but overly packed volume, visual cryptography is reviewed along with its fundamental concepts in theory and practice. The area is absolutely critical at this time for counter-terrorism, corporate security, and in international relations; thus, the topic is of extraordinary interest in a wide variety of fields. One huge advantage of visual cryptography is that it is “a secret sharing technique which allows encryption of an image without requiring any complex computation or knowledge of cryptography.” It should be obvious from the description that this area will be an issue of profound interest and debate as a result. “The design, construction, analysis, and application of visual cryptography schemes (VCSs) are discussed in detail,” according to the publisher’s description of the book.
The authors, from China and Australia, present research on VCS and on aspects of the practice insofar as the ideas of probabilistic, size invariant, threshold, concolorous, and cheating immune components are concerned. Since this is such a highly technical volume, and to ensure a basic comprehension of the key components (probabilistic, size invariant, concolorous, and cheating immune), the definitions should be clear and presented early. Instead, definitions appear scattered and throughout the volume: probabilistic (pp. 14, 41, 83); size invariant (pp. 83, 96); and cheating immune (p. 53). Concolorous is not clearly defined in regard to VCS. The glossary is sparse, but there are basic definitions found there. The index might be referenced as a further aid, but it is very short and not helpful for these basic aspects of VCS.
Nonetheless, VCS is a technique that allows visual information (pictures, text, and so on) to be encrypted in such a way that decryption becomes a mechanical operation that does not require a computer. The authors note that one of the best-known VCS techniques has been credited to Moni Naor and Adi Shamir (1994). It can be clearly understood that there are antecedents of visual cryptography in patents from the 1960s, as well as other antecedents in works on perception and secure communication. Secure communication is of primary interest to the authors in this volume. Finally, and perhaps most importantly, VCS can be used to protect biometric templates in which decryption does not require any complex computations. VCS is readily available to any neophyte.
In spite of the importance of the topic, the editors at Springer should have reviewed the volume more closely before publication. There are a number of troubling editorial issues that appear early in the text and are too numerous to document. A few examples should suffice to make the point: “Evidences shows” (p. v) should agree in subject and verb; a word needs to be supplied, as in “[a] one pad” (p. 1); “complicate” (p. 1) should be complicated; “the information range is much wide” [sic]; and “We notice that, [the] final goal” (p. 23), in which an article should be added.
There are helpful aspects of the text. At the end of each chapter, there are questions and exercises, which may assist the reader in grasping the importance of the material presented. In addition, there are voluminous references that supplement each chapter. There is no bibliography, though, which would have been an important supplement to add.
There are sound references on visual cryptography that interested readers may find more reliable [1,2,3,4,5].