Keyless Cryptography

Mar 27, 2002

Abstract

Key cryptography is a matter of common knowledge. It exploits the fact that legal users have either to share secrete keys initially (conventional cryptography) or to keep in secrete their decrypting keys and distribute publicly encrypting keys (public-key cryptography).But there may be differences between legal and illegal users other than the simple possession of secret keys. This approach offers a new variety of cryptography- so called "keyless" cryptography. Keyless cryptography is based on the distinctions between channels connecting legal users and "wire-tap channels" between legal and illegal users. The main distinction is that legal channels are less noisy sometimes than illegal ones. Next is that illegal users are passive sometimes. It means that they are able to receive the messages only but unable to intervene in this transmissions. The first paper devoted to keyless cryptography ("The wire-tap channel concept") was authored by A. Wyner in 1975. This direction was developing later by many authors: Massey, Huget, Bennet, Brassard, Crepeau, Maurer, speaker and others. In the current presentation we consider different applications of keyless cryptography: key-distribution problem based on wire-tap channel concept type I and type II and on passive eavesdropping (including the enhanced version of "Privacy Amplification Theorem"), anonymous channel, public discussion concept (channel and source models), authentication of users based on noisy channels, some cryptographic protocols (bit commitment,oblivious transfer,distance bounding) based on keyless cryptography. Quantum cryptography is demonstrated as an example of opportunity to create artificially more noisy channel for illegal users. A speculation about applications of wire-tap channel concept to nature and society is discussed also.