Thumbnail-preserving encryption by sum-preserving within blocks based on exponential chaotic mapping

In recent years, chaotic sequences have been widely used in image encryption. Wuqi proposed a new rule which one-dimensional discrete chaotic mapping should follow, based on which a noval one-dimensional chaotic mapping was created from the definition of Lyapunov exponent (LE), and this chaotic mapping was combined with a three-pixel thumbnail-preserved encryption (TPE). Diffrent from the existing TPE schemes, the scheme uses a three-pixel sum preserving encryption (SPE) scheme as an example and uses mathematical expressions to illustrate the encryption and decryption methods. The experimental results show that the proposed chaotic mapping has good chaotic properties. Based on this novel TPE scheme, the encrypted image has both high security and usability, which is also competitive with other schemes.