Ic Card for Encryption or Decryption Process and Encrypted Communication System and Encrypted Communication Method Using the Same

Abstract

It is possible to perform encrypted communication between members of a group while assuring a sufficient security compatible with a change of the members. An IC card having the same fixed code F(a) is distributed to all the staffs of company A. When communication is performed between a staff α and a staff β belonging to the same project group, α of the transmission side writes an arbitrary variable code V(1) in the IC card (100a) so as to generate encryption key information K(a1) according to F(a) and V(1) in the IC card and encrypt data D1 by using K(a1). β of the reception side writes the variable code V(1) received from a in the IC card (100b) so as to generate encryption key information K(a1). By using this K(a1), the encrypted data D2 received is decrypted to obtain data D3. The fixed code F(a) is different for each of the companies and rewrite-disabled so as to assure security.

Description

TECHNICAL FIELD [0001] The present invention relates to an encrypted communication system and an encrypted communication method, and particularly relates to arts of performing encrypted communication using an IC card which executes an encryption or a decryption process. BACKGROUND ART [0002] With the spread of computer networks in recent years, encrypted communication arts have become extremely important and essential. In a general encrypted communication method, data to be subject to transmission is encrypted at a transmitter side and transmitted as encrypted text data to a receiver side, and at the receiver side, the transmitted encrypted text data is decrypted to obtain the original data subject to transmission. Thus to perform encrypted communication between the two sides, in addition to providing means for sending and receiving data, a means for executing an encryption process must be provided at the transmitter side and a means for executing a decryption process must be provid...

AI Technical Summary

Benefits of technology

[0033] According to the present invention, the encryption key information necessary for the encryption process or the decryption process is generated inside the IC card by a computation process based on the two codes of the fixed code and the variable code that are stored inside the IC card. Here, the fixed code is data that has been written into the IC card in advance and is arranged to be non-rewritable. Thus for example, by writing, into IC cards to be issued to a specific company, the same fixed code unique to the company, the fixed code becomes data stored only in the IC cards owned by company staff of the company and sufficient security measures can thus be taken against an unspecified number of persons outside the company. Meanwhile, since the variable code is a code that can be rewritten freely, flexible accommodation is enabled by rewriting the variable code anew each time a change of member of a project team occurs.

Problems solved by technology

That is, the decryption cannot be performed as long as the secret encryption key information is not provided.

Obviously in such a case, conventional encrypted communication arts enable encrypted communication of a mode such that deciphering cannot be performed by company staff not involved in the specific project.

However, a project team in a company is liable to undergo a change of members frequently through dissolution, joining of groups, addition of new members, leaving of existing members, etc.

However, flexibility and security are generally conflicting elements and if flexibility is provided, security is inevitably compromised accordingly.

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