ENCRYPTION METHOD AND APPARATUS WITH VARIABLE ENCRYPTION STRENGTH

摘要

An encryption method and apparatus in which a cryptographic encryption key (K) for use to encrypt or decrypt communications is first derived from a cryptographic key (K>d<) provided by a user. The derived encryption key is used to encrypt or decrypt communications at a selected level of encryption strength. The level of encryption strength is selected in accordance with whether or not the cryptographic key provided by the user has a particular property, such as including a particular sequence of bits, dividing exactly by a particular number, or whether a particular cryptographic check value (S) can be derived from it. A method and apparatus for generating suitable cryptogrpjhic keys are also described.