KEY EXCHANGE SYSTEM, INFORMATION PROCESSOR, KEY EXCHANGE METHOD AND PROGRAM

• Main Authors: MURAKAMI KEIZO, OKANO HIROKI, KOBAYASHI TETSUTARO, YONEYAMA KAZUKI, NAKABAYASHI MISATO
• Format: Patent
• Language: English; Japanese
• Published: 02.08.2021
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHICCOMMUNICATION

To provide an asynchronous ID-basis multi party key exchange protocol.SOLUTION: A key exchange system 1 includes: a first terminal 11; one or more second terminals 121 to 12n belonging to the same group; and an auxiliary server 20 for supporting a group key exchange between the first terminal and the second terminal. The first terminal comprises: first generation means which uses a public key generated in the auxiliary server to generate a group key generation key and a cryptogram to which the generation key is encrypted; second generation means for generating a group key by using a generating key; and third generation means which encrypts a cryptogram or generates signcryption information. The auxiliary server has forth generation means for generating information to which the information generated by the third generation means is re-encrypted by using a pre-calculation key of a first terminal generation. The second terminal comprises: fifth generation means for generating a cryptogram by decrypting the information generated by the fourth generation means; and sixth generation means for generating a group key by using a generation key which is obtained by decrypting the cryptogram in the auxiliary server.SELECTED DRAWING: Figure 1 【課題】非同期型のＩＤベース多者間鍵交換プロトコルを提供する。【解決手段】第１端末１１と、同一グループに属する１以上の第２端末１２１〜１２ｎと、第１端末と第２端末間でグループ鍵交換を補助する補助サーバ２０と、を含む鍵交換システム１であって、第１端末は、補助サーバで生成の公開鍵を用い、グループ鍵生成の生成鍵と該生成鍵を暗号化した暗号文とを生成の第１生成手段と、生成鍵を用いグループ鍵生成の第２生成手段と、暗号文を暗号化又はサインクリプション情報を生成する第３生成手段とを有する。補助サーバは、第１端末生成の事前計算鍵を用い、第３生成手段生成の情報を再暗号化した情報を生成する第４生成手段を有する。第２端末は、第４生成手段で生成の情報を復号して暗号文を生成する第５生成手段と、暗号文を補助サーバで復号して得た生成鍵を用い、グループ鍵を生成する第６生成手段とを有する。【選択図】図１