| 摘要 |
A communication method using a common key by which the security of a cryptographic key against various kinds of attacks can be improved in a system which performs cryptographic communication between entities by using a common cryptographic key. When cryptographic communication is performed between entities (i) and (j), both entities (i) and (j) prepare a common cryptographic key by applying an identifier converting algorithm and secret personal keys distributed from the center in advance to the identifiers of the communication partners (Procedure 3). The transmitting side, in addition, prepares a telegraphic message for cryptographic communication by preparing one-time random number data for cryptographic communication and encoding the random number data by using the common cryptographic key and a correspondence by using the random number data, and then, combining the encoded data and correspondence together. The receiving side decodes the encoded random number data of the telegraphic message by using the common cryptographic key and the correspondence by using the decoded random number data.
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