Malicious KGC attacks in certificateless cryptography

Man Ho Au, Yi Mu, Jing Chen, Duncan S. Wong, Joseph K. Liu, Guomin Yang

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206 Citations (Scopus)


Identity-based cryptosystems have an inherent key escrow issue, that is, the Key Generation Center (KGC) always knows user secret key. If the KGC is malicious, it can always impersonate the user. Certificateless cryptography, introduced by Al-Riyami and Paterson in 2003, is intended to solve this problem. However, in all the previously proposed certificateless schemes, it is always assumed that the malicious KGC starts launching attacks (so-called Type II attacks) only after it has generated a master public/secret key pair honestly. In this paper, we propose new security models that remove this assumption for both certificateless signature and encryption schemes. Under the new models, we show that a class of certificateless encryption and signature schemes proposed previously are insecure. These schemes still suffer from the key escrow problem. On the other side, we also give new proofs to show that there are two generic constructions, one for certificateless signature and the other for certificateless encryption, proposed recently that are secure under our new models.

Original languageEnglish
Title of host publicationProceedings of the 2nd ACM Symposium on Information, Computer and Communications Security, ASIACCS '07
Place of PublicationNew York NY USA
PublisherAssociation for Computing Machinery (ACM)
Number of pages10
ISBN (Print)1595935746, 9781595935748
Publication statusPublished - 2007
Externally publishedYes
EventACM Symposium on Information, Computer and Communications Security 2007 - Singapore, Singapore
Duration: 20 Mar 200722 Mar 2007
Conference number: 2nd


ConferenceACM Symposium on Information, Computer and Communications Security 2007
Abbreviated titleAsiaCCS 2007
Internet address

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