Encrypting conversion apparatus, decrypting conversion apparatus, cryptographic communication system, and electronic toll collection apparatus

Abstract

An encrypting conversion apparatus, a decrypting conversion apparatus, a cryptographic communication system and an electronic toll collection apparatus are provided which are capable of changing algorithms of cryptographic conversion to hide the algorithm in use from a third party so that the apparatuses and system are resistant against a cryptographic attack from the third party and can operate at high speed. In the cryptographic communication system.

Description

[0001] This application relates to an application U.S. Ser. No. 09 / 130,529 filed on Aug. 4, 1998 by Makoto Aikawa et al entitled "DATA ENCRYPTING / DECRYPTING CONVERSION METHODS AND APPARATUSES AND DATA COMMUNICATION SYSTEM ADOPTING THE SAME" and assigned to the present assignee. The disclosure of that application is hereby incorporated by reference into the disclosure of this application.[0002] 1. Field of the Invention[0003] The present invention relates to techniques for encrypting / decrypting digital data transferred among computers, household information processing appliances, and electronic toll collection apparatuses.[0004] 2. Description of the Related Art[0005] Enciphering techniques for preventing an illegal copy of digital data are essential for digital household information processing appliances. For example, if digital visual data received by a digital broadcasting receiver is digitally recorded in a digital video recorder and the digital visual data has a copyright, both ...

AI Technical Summary

Problems solved by technology

For example, a cryptographic attack can be made difficult by increasing the number of repetitions of simple conversions to further disturb statistical characteristics of cipher texts.

However, if the number of conversion repetitions is increased, the processing time required for cryptographic conversion becomes long.

Therefore, a security reinforcing countermeasure through an increase in the number of repetitions of simple conversions is not suitable for real time cryptograph in the copyright protection system.

In an electronic toll collection system (ETC) of a toll speed-way which has lately attracted attention, a real-time cryptographic processing is required, so that the problem as mentioned above arises.

Images