Patent ID: 6272221
Filing Date: 2001-08-07
Classification: H04L

Abstract:
An encryption apparatus for producing a ciphertext string corresponding to a plaintext string based on an encryption key, said apparatus comprising:at least one conversion means for performing linear or non-linear conversion of a bit string;an intermediate-key generating means for generating an initial-value of an intermediate-key by performing linear or non-linear bit-string conversion for an inputted intermediate-key; andan intermediate-key memory means for updating and storing the intermediate-key using an intermediate-key update-information;wherein at least one of said conversion means forming a pair with said intermediate-key memory means, at least one of said paired conversion means is subjected to control of an intermediate-key stored in said intermediate-key memory means and generates an intermediate-key update-information for updating the intermediate-key whenever the bit string conversion is performed and transmits said intermediate-key update-information to said intermediate-key memory means forming a pair with said conversion means;said intermediate-key memory means further comprises an initial value memory for storing a predetermined number of the initial-values which are delivered from said intermediate-key generating means;and said apparatus further comprises a selecting means for selecting at least one initial-value among initial-values stored in said intermediate-key memory means whenever the bit string conversion is performed, controlling the conversion means in a pair and updating the intermediate-key based on said intermediate-key update-information.