Certificateless Public Key Cryptography

Abstract

Abstract. This paper introduces and makes concrete the concept of certificateless public key cryptography (CL-PKC), a model for the use of public key cryptography which avoids the inherent escrow of identitybased cryptography and yet which does not require certificates to guarantee the authenticity of public keys. The lack of certificates and the presence of an adversary who has access to a master key necessitates the careful development of a new security model. We focus on certificateless public key encryption (CL-PKE), showing that a concrete pairing-based CL-PKE scheme is secure provided that an underlying problem closely related to the Bilinear Diffie-Hellman Problem is hard.

On Constructing Certificateless Cryptosystems from Identity Based Encryption

“…In 2003, Al-Riyami and Paterson [2] invented a paradigm called certificateless public key cryptography (CL-PKC) which is intermediate between identitybased [27,12] and traditional PKI-supported cryptography. The concept was introduced to suppress the inherent key-escrow property of identity-based cryptosystems (ID-PKC) without losing their most attractive advantage which is the absence of digital certificates and their important management overhead.…”

“…Independently of [2] and a bit earlier, Gentry [22] introduced a different but related concept named certificate based encryption (CBE) for which a signature analogue was studied in [24]. This approach is closer to the context of a traditional PKI model as it involves a certification authority (CA) providing an efficient implicit certification service for clients' public keys.…”

“…Although very different at first glance, the CBE and CLE concepts were first argued [2] to be closely related and both constructions of [2,22] use the properties of pairings. A subsequent work of Yum and Lee considered the relations between identity-based (IBE), certificate based (CBE) and certificateless encryption schemes (CLE) and established a result of essential equivalence [31] between the three primitives but this result does not hold for the strongest security model developed in [2] for CLE schemes.…”

“…A subsequent work of Yum and Lee considered the relations between identity-based (IBE), certificate based (CBE) and certificateless encryption schemes (CLE) and established a result of essential equivalence [31] between the three primitives but this result does not hold for the strongest security model developed in [2] for CLE schemes. The same authors also proposed generic constructions of certificateless signatures [30] and encryption schemes [29] but only established the security of their designs in security models that are seemingly undermined w.r.t.…”

“…The same authors also proposed generic constructions of certificateless signatures [30] and encryption schemes [29] but only established the security of their designs in security models that are seemingly undermined w.r.t. the original model considered in [2] for the public key encryption case.…”