Chapter 2Fundamentals of Image Encryption for Wireless Communications
2.1 Introduction
Fifty years ago, Claude Shannon pointed out that the fundamental techniques to encrypt a block of symbols are confusion and diffusion. Confusion can obscure the relationship between the plaintext and the ciphertext, and diffusion can spread the changes throughout the whole ciphertext. Substitution is the simplest method of confusion, and permutation is the simplest method of diffusion. Substitution replaces a symbol with another one, while permutation changes the sequence of the symbols in the block to make them unreadable. If applied independently, neither substitution nor permutation works very well [8].
These two techniques are still the foundations of ...
