ID-based Ring Signature and Proxy Ring Signature Schemes from Bilinear Pairings

In 2001, Rivest et al. firstly introduced the concept of ring signatures. A ring signature is a simplified group signature without any manager. It protects the anonymity of a signer. The first scheme proposed by Rivest et al. was based on RSA cryptosystem and certificate based public key setting. The first ring signature scheme based on DLP was proposed by Abe, Ohkubo, and Suzuki. Their scheme is also based on the general certificate-based public key setting too. In 2002, Zhang and Kim proposed a new ID-based ring signature scheme using pairings. Later Lin and Wu proposed a more efficient ID-based ring signature scheme. Both these schemes have some inconsistency in computational aspect. In this paper we propose a new ID-based ring signature scheme and a proxy ring signature scheme. Both the schemes are more efficient than existing one. These schemes also take care of the inconsistencies in above two schemes.Comment: Published with ePrint Archiv

A note on the Certificateless Multi-receiver Signcryption Scheme

Certificateless cryptography aims at combining the advantages of identity based and public key cryptography, so as to avoid the key escrow problem inherent in the identity based system and cumbersome certificate management in public key infrastructure. Signcryption achieves confidentiality and authentication simultaneously in an

Identity based cryptography from bilinear pairings

This report contains an overview of two related areas of research in cryptography which have been prolific in significant advances in recent years. The first of these areas is pairing based cryptography. Bilinear pairings over elliptic curves were initially used as formal mathematical tools and later as cryptanalysis tools that rendered supersingular curves insecure. In recent years, bilinear pairings have been used to construct many cryptographic schemes. The second area covered by this report is identity based cryptography. Digital certificates are a fundamental part of public key cryptography, as one needs a secure way of associating an agent’s identity with a random (meaningless) public key. In identity based cryptography, public keys can be arbitrary bit strings, including readable representations of one’s identity.Fundação para a Ci~Encia e Tecnologia - SFRH/BPD/20528/2004

The Insecurity of Two Proxy Signcryption Schemes: Proxy Credential Forgery Attack and How to Prevent It

Securing different online e-business activities usually requires applying different cryptographic algorithms. The proxy signcryption algorithms are designed for applications such as online proxy auction or online proxy signatures on business contracts, which require a proxy agent to sign on confidential messages. This paper proposes a proxy credential forgery attack to two recent proxy signcryption schemes in the literature. Using the attack, a malicious proxy signer can create a fake proxy credential from his original credential to extend his signing power. Simple modifications to these two schemes are also provided in this paper to prevent the attack without adding too much computational complexity. In addition to the contribution of introducing a new type of attacks to signcryption schemes, the paper also points out that, while designing a secure proxy signcryption scheme, not only the unforgeability of proxy signatures is important, but also that of proxy credentials as well

Anonymous ID Based Signcryption Scheme for Multiple Receivers

Anonymous signcryption is synonyms of ring signcryption which provides anonymity of the sender along with the advantages of signcryption. Multi receiver signcryption is suited for situation where a sender wants to send a message to multiple receivers in the confidential and authenticated way. This paper proposes an identity based anonymous signcryption scheme in multi-receiver setting. It also provides proofs of provable security of the proposed scheme under some computationally difficult problems

Identity Based Public Verifiable Signcryption Scheme

Signcryption as a single cryptographic primitive offers both confidentiality and authentication simultaneously. Generally in signcryption schemes, the message is hidden and thus the validity of the ciphertext can be verified only after unsigncrypting the ciphertext. Thus, a third party will not be able to verify whether the ciphertext is valid or not. Signcryption schemes that allow any user to verify the validity of the ciphertext without the knowledge of the message are called public verifiable signcryption schemes. Third Party verifiable signcryption schemes allow the receiver to convince a third party, by providing some additional information along with the signcryption other than his private key with/without exposing the message. In this paper, we show the security weaknesses in three existing schemes \cite{BaoD98}, \cite{TsoOO08} and \cite{ChowYHC03}. The schemes in \cite{BaoD98} and \cite{TsoOO08} are in the Public Key Infrastructure (PKI) setting and the scheme in \cite{ChowYHC03} is in the identity based setting. More specifically, \cite{TsoOO08} is based on elliptic curve digital signature algorithm (ECDSA). We also, provide a new identity based signcryption scheme that provides public verifiability and third party verification. We formally prove the security of the newly proposed scheme in the random oracle model

Identity based signcryption schemes without random oracles

Signcryption is a cryptographic primitive which performs encryption and signature in a single logical step with the cost lower than signature-then-encryption approach.. In this paper we gave attacks on confidentiality and unforgeability of two identity based signcryption schemes without random oracles. Further we proposed an improved identity based signcryption scheme without random oracles. We also proposed an identity based public verifiable signcryption scheme with third party verification without random oracles