Paper 2008/074

On the Chikazawa-Inoue ID based key system

Bae Eun Jung and Hee Jean Kim


In this paper, we show that Chikazawa-Inoue ID-based key system is insecure by collusion, where Chikazawa-Inoue ID-based key system means the key parameters established during the initiation phase. We describe an algorithm factorizing a public key of Trust Center. Since our attack is based on only the key system and has no relation with specific key sharing protocols, it can be applied to all variant protocols of Chikazawa-Inoue ID based key sharing protocol. From this analysis, we obtain conclusions that Chikazawa-Inoue ID-based key system cannot be used any more for any application protocols.

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Publication info
Published elsewhere. Integer factorization, collusion attack, Chikazawa-Inoue ID key system
public keyinteger factorizationcollusion attackChikazawa-Inoue ID based key system
Contact author(s)
be jung @ samsung com
2008-02-19: last of 2 revisions
2008-02-18: received
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      author = {Bae Eun Jung and Hee Jean Kim},
      title = {On the Chikazawa-Inoue ID based key system},
      howpublished = {Cryptology ePrint Archive, Paper 2008/074},
      year = {2008},
      note = {\url{}},
      url = {}
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