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Abstract

A method and a system for cipher key distribution realizing an effective prevention of the illegitimate use and the illegitimate charging. A key request signal containing a first random number generated at each user terminal is transmitted from each user terminal to the key center, so as to indicate the cipher key required at each user terminal to the key center, and a terminal check signal containing a second random number generated at the key center is transmitted from the key center to each user terminal. Then, a terminal response signal containing the second random number and a value based on the first random number obtained according to the first random number generated at each user terminal and the second random number contained in the terminal check signal is transmitted from each user terminal to the key center, and the second random number and the value based on the first random number contained in the terminal response signal are checked at the key center, according to the second random number generated at the key center and the first random number contained in the key request signal, so as to confirm a legitimacy of an access from each user terminal. Then, a key distribution signal containing the cipher key requested by the key request signal is transmitted from the key center to each user terminal, only when the legitimacy of the access from each user terminal is confirmed.

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First Claim