What is kleptography?
The notion of an asymmetric backdoor was introduced in [YY96b]. A kleptographic attack is an attack in which a malicious designer deploys an asymmetric backdoor. In a kleptographic attack, there is an explicit distinction between confidentiality of the messages (e.g., the private keys of the users) and awareness that the attack is taking place. A secure kleptographic attack is undetectable as long as the cryptosystem is a black-box. Also, if the black-box is opened, it may be evident that a kleptographic attack is underway, but confidentiality is preserved. In other words, a kleptographic attack is an asymmetric backdoor that can only be used by the designer that carries out the attack. This subject of research is called Kleptography: the study of stealing information securely and subliminally (see also [YY97b,WL02,CS03]). Kleptography is a natural extension of the theory of subliminal channels. Prior to the advent of asymmetric backdoors, scientific research on backdoors in cryptosyst
