451 research outputs found
TOWARD CERTIFICATELESS SIGNCRYPTION SCHEME WITHOUT RANDOM ORACLES
Signcryption is a useful paradigm which simultaneously offers both the functions of encryption and signature in a single logic step. It would be interesting to make signcryption certificateless to ease the heavy burden of certificate management in traditional public key cryptography (PKC) and solve the key escrow problem in Identity-based public key cryptography (ID-PKC). Most certificateless signcryption (CL-SC) schemes are constructed in the random oracle model instead of the standard model. By exploiting Bellare and Shoup\u27s one-time signature, Hwang et al.\u27s certificateless encryption and Li et al.\u27s identity-based signcryption, this paper proposes a new CL-SC scheme secure in the standard model. It is proven that our CL-SC scheme satisfies semantic security and unforgeability against the outside adversary and malicious-but-passive key generation center (KGC) assuming the hardness of bilinear decision Diffie-Hellman (BDDH) and computational Diffie-Hellman (CDH) problems. Our security proofs do not depend on random oracles
Provably Secure Generic Construction of Certificate Based Signature from Certificateless Signature in Standard Model
Both certificateless cryptography (CLC) and certificate-based cryptography (CBC) are two novel public key paradigms which combine the merits of traditional public key cryptography (PKC) and
identity-based cryptography (IBC). They succeed in avoiding the key escrow problem in IBC and reducing the public key management overhead in traditional PKC. This paper deals with the generic construction of certificate based signature (CBS) from certificateless signature (CLS). Wu et al. proposed the first generic conversion from CLS to CBS provably secure in the random oracle model.
This paper proposes an intuitive, simple and provably secure generic conversion from CLS to CBS. The security for this conversion is proved in the standard model. To develope the security proof of this conversion, we put forth one novel security model which introduces a previously neglected notrivial attack and better captures the CLS security notion. Following this generic conversion, a provably secure CLS scheme is constructed as an example
Practical Certificateless Aggregate Signatures From Bilinear Maps
Aggregate signature is a digital signature with a striking property that anyone can aggregate n individual signatures on n different messages which are signed by n distinct signers, into a single compact signature to reduce computational and storage costs. In this work, two practical certificateless aggregate signature schemes are proposed from bilinear maps. The first scheme CAS-1 reduces the costs of communication and signer-side computation but trades off the storage, while CAS-2 minimizes the storage but sacrifices the communication costs. One can choose either of the schemes by consideration of the application requirement. Compare with ID-based schemes, our schemes do not entail public key certificates as well and achieve the trust level 3, which imply the frauds of the authority are detectable. Both of the schemes are proven secure in the random oracle model by assuming the intractability of the computational Diffie-Hellman problem over the groups with bilinear maps, where the forking lemma technique is avoided
Certificateless KEM and Hybrid Signcryption Schemes Revisited
Often authentication and confidentiality are required as simultaneous key requirements in many cryptographic applications. The cryptographic primitive called signcryption effectively implements the same and while most of the public key based systems are appropriate for small messages, hybrid encryption (KEM-DEM) provides an efficient and practical way to securely communicate very large messages. Recently, Lippold et al. \cite{GCJ09} proposed a certificateless KEM in the standard model and the first certificateless hybrid signcryption scheme was proposed by Fagen Li et al. \cite{LST09}. The concept of certificateless hybrid signcryption has evolved by combining the ideas of signcryption based on tag-KEM and certificateless cryptography. In this paper, we show that \cite{GCJ09} is not Type-I CCA secure and \cite{LST09} is existentially forgeable. We also propose an improved certificateless hybrid signcryption scheme and formally prove the security of the improved scheme against both adaptive chosen ciphertext attack and existential forgery in the appropriate security models for certificateless hybrid signcryption
An efficient certificateless authenticated key agreement protocol without bilinear pairings
Certificateless public key cryptography simplifies the complex certificate
management in the traditional public key cryptography and resolves the key
escrow problem in identity-based cryptography. Many certificateless
authenticated key agreement protocols using bilinear pairings have been
proposed. But the relative computation cost of the pairing is approximately
twenty times higher than that of the scalar multiplication over elliptic curve
group. Recently, several certificateless authenticated key agreement protocols
without pairings were proposed to improve the performance. In this paper, we
propose a new certificateless authenticated key agreement protocol without
pairing. The user in our just needs to compute five scale multiplication to
finish the key agreement. We also show the proposed protocol is secure in the
random oracle model
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