The invention is a cryptographic system using chaotic dynamics. A chaotic
system is used to generate a public key and an adjustable back door from
a private key. The public key is distributed and can be used in a public
key encryption system. The invention can also be used for authentication
purposes. The adjustable back door of the invention can be used in
conjunction with the public key to derive the private key. The degree of
difficulty involved in deriving the private key is dependent on the
adjustable back door. That is the value of the back door can be adjusted
to vary the difficulty involved in deriving the private key.