Key distribution method and system in secure broadcast communication

A cipher communication system, comprising:

• a broadcasting station;
• a server;
• and
• a plurality of receiver units connected to said server, each configured to decode an encrypted data broadcasted from said broadcasting station by obtaining permission information from said server,
• wherein said server comprises:
• a unit for storing individual information per receiver unit transmitted from a broadcasting station;
• a unit for receiving authentication data from a receiver unit and performing authentication;
• and
• a unit for transmitting said individual information to a corresponding receiver unit when authentication is made,
• wherein said receiver units each comprises:
• a unit for transmitting authentication data to said server;
• and
• a unit for decoding said encrypted data on a basis of said individual information transmitted from said server and key information transmitted from said broadcasting station.

A cipher communication method including a server, a plurality of receiver units connected to said server, a broadcasting station which performs communications with designated receiver units, comprising:

• generating, at said broadcasting station, confidential key information and preliminarily distributing said confidential key information to said plurality of receiver units;
• generating, at said broadcasting station, encrypted text (C) by encrypting data (P) to be transmitted with encrypting common key (K), and generating key distribution data (W) necessary for calculation of said common key (K);
• broadcasting, at said broadcasting station, said encrypted text (C) and said key distribution data (W);
• generating, at said broadcasting station, individual information per individual receiver unit to be transmitted to said designated receiver units, and transmitting said individual information to said server;
• receiving, at said server, said individual information transmitted from said broadcasting station;
• receiving, at said server, authentication data from a receiver unit and performing authentication;
• and
• transmitting, at said server, said individual information to a corresponding receiver unit when authentication is made;
• transmitting, at said receiver unit, said authentication data to said server;
• and
• calculating, at said receiver unit, said common key (K) on a basis of said individual information transmitted from said server, said confidential key information preliminarily distributed from said broadcasting station and said key distribution data (W) broadcasted from said broadcasting station, and decoding said data (P) from said encrypted text (C).

A cipher communication method including a broadcasting station, a server and a plurality of receiver units connected to said server, each adapted to decode an encrypted data broadcasted from said broadcasting station by obtaining permission information from said server, comprising:

• storing, at said server, individual information per receiver unit transmitted from said broadcasting station;
• receiving, at said server, authentication data from a receiver unit for performing authentication;
• transmitting, at said server, said individual information to a corresponding receiver unit when authentication is made;
• transmitting, at said receiver unit, authentication data to said server;
• and
• decoding, at said receiver unit, said encrypted data on a basis of said individual information transmitted from said server and key information transmitted from said broadcasting station.