| 摘要 |
According to the present invention, a secret key cryptosystem and tamper-proof hardware are used to realize a pseudo public key cryptosystem at a low cost. A trap-door one-way function is substantially realized with the use of tamper-proof hardware. Each user performs communication using equipment provided with hardware having the same capabilities described below. Such hardware retains association between an ID and a key. In response to a request from a user, the hardware issues and stores an ID, and it can perform decryption and generation of a MAC (message authentication code) with a key associated with the ID. A user publishes his ID. When performing encryption, a message sender encrypts a message using the published ID. A third person can perform decryption with the ID only by analyzing the mechanism in the hardware. However, the hardware has a capability of destroying itself when such an act is attempted.
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