A New Double Security And Protection Schemes In Cloud Storage

The first article is his/her secret key stored in the computer. The second thing is a singleprivatesanctuary device which joins to the computer. It is terrible to decrypt the ciphertext wanting both pieces. Supplementarysignificantly, once the haven device is stolen or lost, this device is rescinded. It cannot be used to decrypt any ciphertext. This can be finished by the cloud server which will instantlyaccomplish some algorithms to revolution the existing cipher text to be un-decrypt able by this device. This route is utterlytranslucent to the sender. Likewise, the cloud server cannot decrypt any ciphertext at any time. The safekeeping and efficiency enquiry show that our system is not only sheltered but also useful

An Efficient Certificate-Based Designated Verifier Signature Scheme

Certificate-based public key cryptography not only solves certificate revocation problem in traditional PKI but also overcomes key escrow problem inherent in identity-based cryptosystems. This new primitive has become an attractive cryptographic paradigm. In this paper, we propose the notion and the security model of certificate-based designated verifier signatures (CBDVS). We provide the first construction of CBDVS and prove that our scheme is existentially unforgeable against adaptive chosen message attacks in the random oracle model. Our scheme only needs two pairing operations, and the signature is only one element in the bilinear group G1. To the best of our knowledge, our scheme enjoys shortest signature length with less operation cost

A Provably Secure Certificate Based Ring Signature Without Pairing

Abstract In Eurocrypt 2003, Gentry introduced the notion of certificate-based encryption. The merit of certificatebased encryption lies in implicit certificate and no private key escrow. This feature is desirable especially for the efficiency and the real spontaneity of ring signature, which involve a large number of public keys in each execution. In this paper, we propose an efficient certificatebased ring signature scheme which does not require any pairing computation. Furthermore, this scheme is proven secure under the Discrete Logarithm assumption in the random oracle model. To the best of authors' knowledge, this is the first construction of certificate-based ring signature scheme in the literature that has such kind of feature

Cryptanalysis of Three Certificate-Based Authenticated Key Agreement Protocols and a Secure Construction

Certificate-based cryptography is a new public-key cryptographic paradigm that has very appealing features, namely it simplifies the certificate management problem in traditional public key cryptography while eliminating the key escrow problem in identity-based cryptography. So far, three authenticated key agreement (AKA) protocols in the setting of certificate-based cryptography have been proposed in the literature. Unfortunately, none of them are secure under the public key replacement (PKR) attack. In this paper, we first present a security model for certificate-based AKA protocols that covers the PKR attacks. We then explore the existing three certificate-based AKA protocols and show the concrete attacks against them respectively. To overcome the weaknesses in these protocols, we propose a new certificate-based AKA protocol and prove its security strictly in the random oracle model. Performance comparison shows that the proposed protocol outperforms all the previous certificate-based AKA protocols

Certificate-Based Signcryption: Security Model and Efficient Construction

Signcryption is an important cryptographic primitive that simultaneously achieves confidentiality and authentication in an efficient manner. In 2008, Luo et al. introduced the notion of certificate-based signcryption and proposed the first construction of certificate-based signcryption. However, their scheme is insecure under the key replacement attack and also does not provide insider security. To overcome these disadvantages, we introduce a strengthened security model of certificate-based signcryption in this paper. The new security model accurately models insider security and the key replacement attacks that might be attempted by an adversary in a real certificate-based signcryption system. We also propose a new certificate-based signcryption scheme that reaches insider security and resists key replacement attacks. We show that this scheme is both chosen-ciphertext secure and existentially unforgeable in the random oracle model. Furthermore, performance analysis shows that the proposed scheme is efficient and practical

RingCT 2.0: A Compact Accumulator-Based (Linkable Ring Signature) Protocol for Blockchain Cryptocurrency Monero

In this work, we initially study the necessary properties and security requirements of Ring Confidential Transaction (RingCT) protocol deployed in the popular anonymous cryptocurrency Monero. Firstly, we formalize the syntax of RingCT protocol and present several formal security definitions according to its application in Monero. Based on our observations on the underlying (linkable) ring signature and commitment schemes, we then put forward a new efficient RingCT protocol (RingCT 2.0), which is built upon the well-known Pedersen commitment, accumulator with one-way domain and signature of knowledge (which altogether perform the functions of a linkable ring signature). Besides, we show that it satisfies the security requirements if the underlying building blocks are secure in the random oracle model. In comparison with the original RingCT protocol, our RingCT 2.0 protocol presents a significant space saving, namely, the transaction size is independent of the number of groups of input accounts included in the generalized ring while the original RingCT suffers a linear growth with the number of groups, which would allow each block to process more transactions

Certificate based (linkable) ring signature

In this paper, we propose a new notion called Certificate Based Ring Signature (CBRS) that follows the idea of Certificate Based Encryption (CBE) presented by Gentry in EuroCrypt 2003. It preserves the advantages of CBE such as implicit certificate and no private key escrow. At the same time it inherits the properties of normal ring signature such as anonymity and spontaneity. We provide its security model and a concrete implementation. In addition, we also propose a variant of CBRS, called Certificate Based Linkable Ring Signature (CBLRS). It is similar to CBRS, except with linkability. That is, it allows the public to verify whether two given signatures are generated by the same signer, yet preserves the anonymity of this user. It can be seen as the Certificate Based version of normal linkable ring signature