Cipher-key distribution system

• US 5,029,208 A
• Filed: 03/05/1990
• Issued: 07/02/1991
• Est. Priority Date: 03/03/1989
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Tanaka, Kazue
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Cain, David
• Application Number:
  US07/488,952
• Time in Patent Office: 484 Days
• Field of Search: 380/21, 380/30, 380/46
• US Class Current: 380/279
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0844 with user authentication or key authentication, e.g. ElGamal, MTI, MQV-Menezes-Qu-Vanstone protocol or Diffie-Hellman protocols using implicitly-certified keys

Abstract

A cipher-key distribution system used in a one-way communication from a first party to a second party. The cipher-key distribution system is composed of a first subsystem, a second subsystem, and a common file which stores information publically accessible by the first and second subsystems. The first subsystem generates a cipher-key based on a constant, receiving party identifying information, a random number, and public information from the common file. The first subsystem also generates a key distributing code based on a constant, a random number and a first secret information and transfers the key distributing code to a second subsystem. The second subsystem receives the key distributing code and information for identifying the first party and generates a second cipher-key identical to the cipher-key generated by the first subsystem. The second cipher-key is created from the information for identifying the first party, a second secret information, and the key distributing code. The first subsystem, instead of generating and transmitting a key distributing code, may simply transmit information for identifying the first communicating party to the second subsystem.

Claims

1. A cipher-key distribution system for distributing a cipher key for use in cipher communication by a first communicating party with a second communicating party, provided with:

a common file for storing public information in a position indicated by receiving party identifying information, and first and second subsystems, wherein;

said first subsystem comprises;

reading means for reading said public information out of said common file;

random number generating means for generating random numbers;

first cipher-key generating means for generating a cipher key based on a constant, said receiving party identifying information, a random number generated by said random number generating means and the public information read out by said reading means;

first secret information holding means for holding a first secret information of said first communicating party using said first subsystem, said first secret information not accessible to said second communicating party;

key distributing code generating means for generating a key distributing code based on said constant, said random number and the first secret information given from said first secret information holding means; and

transmitting means for transmitting the key distributing code generated by the key distributing code generating means and information for identifying the first communicating party, and

said second subsystem comprises;

receiving means for receiving the key distributing code and the information for identifying the first communicating party from said transmitting means of the first subsystem;

constant holding means for holding the constant;

second secret information holding means for holding the second secret information of said second communicating party using said second subsystem, said second secret information accessible only to said second communicating party; and

second cipher-key generating means for generating a cipher key, which is identical with the cipher-key generated by said first cipher-key generating means, based on the key distributing code and information for identifying the first communicating party from said receiving means, the constant from said constant holding means and the second secret information from said second secret information holding means.

3. The cipher-key distribution system for distributing a cipher key for use in cipher communication by a first communicating party with a second communicating party, as claimed in claim 1, wherein the first subsystem further has a personal file for storing part of the public information stored in the common file.

4. The cipher-key distribution system for distributing a cipher key for use in cipher communication by a first communicating party with a second communicating party, as claimed in claims 1, 2 or 3, wherein the first subsystem further has verifying means for verifying the public information read out of the common file.

5. The cipher-key distribution system for distributing a cipher key for use in cipher communication by a first communicating party with a second communicating party, as claimed in claims 1 or 3, wherein the second subsystem further has verifying means for verifying the information received from said first subsystem.

2. A cipher-key distribution system for distributing a cipher key for use in cipher communication by a first communicating party with a second communicating party, provided with:

common file means for storing public information in a position indicated by receiving party identifying information, and first and second subsystems, wherein;

said first subsystem comprises;

first reading means for reading said public information out of said common file means;

first secret information holding means for holding a first secret information of said first communication party using said first subsystem said first secret information not accessible to said second communicating party;

first cipher-key generating means for generating a cipher key based on a constant, receiving party identifying information, the public information read out by said first reading means and the first secret information from said first secret information holding means; and

transmitting means for transmitting information for identifying the first communicating party using this subsystem, and

said second subsystem comprises;

receiving means for receiving the information for identifying the first communicating party given from said transmitting means;

second reading means for reading said public information out of said common file means;

constant holding means for holding the constant;

second secret information holding means for holding the second secret information of said second communicating party using said second subsystem said second secret information accessible only to said second communicating party; and

second cipher-key generating means for generating a cipher key, which is identical with the cipher-key generated by said first cipher-key generating means, based on the constant from said constant holding means, the second secret information from said second secret information holding means, the public information given from said second reading means, and said information for identifying the first communicating party from said receiving means.