Certificate-based Encryption Scheme Research Articles

Improved Certificate-Based Encryption Scheme in the Big Data: Combining AES and (ECDSA – ECDH)

Big data usually running in large-scale and centralized key management systems. However, the centralized key management systems are increasing the problems such as single point of failure, exchanging a secret key over insecure channels, third-party query, and key escrow problem. To avoid these problems, we propose an improved certificate-based encryption scheme that ensures data confidentiality by combining symmetric and asymmetric cryptography schemes. The combination can be implemented by using the Advanced Encryption Standard (AES) and Elliptic Curve Diffie-Hellman (ECDH). The proposed scheme is an enhanced version of the Certificate-Based Encryption (CBE) scheme and preserves all its advantages. However, the key generation process in our scheme has been done without any intervention from the certificate issuer and avoiding the risk of compromised CA. The Elliptic Curve Digital Signature Algorithm (ECDSA) has been used with the ECDH to handle the authentication of the key exchange. The proposed scheme is demonstrated on a big dataset of social networks. The scheme is analyzed based on security criteria that have been compared with the previous schemes to evaluate its performance.

Certificate-Based Encryption Resilient to Continual Leakage in the Standard Model

The security for many certificate-based encryption schemes was considered under the ideal condition, where the attackers rarely have the secret state for the solutions. However, with a side-channel attack, attackers can obtain partial secret values of the schemes. In order to make the scheme more practical, the security model for the certificate-based encryption which is resilient to continual leakage is first formalized. The attackers in the security model are permitted to get some secret information continuously through the side-channel attack. Based on the certificate-based key encapsulation scheme, a novel certificate-based encryption scheme is proposed, which is resilient to the continual leakage. In the standard model, the new scheme we propose is proved to be secure under the decisional truncated q-augmented bilinear Diffie–Hellman exponent hard problem and the decisional 1-bilinear Diffie–Hellman inversion hard problem. Additionally, the new scheme can resist the chosen-ciphertext attack. Moreover, a comparison is performed with other related schemes, where the proposed solution further considers the continual leakage-resilient property and exhibits less computation cost.

Leakage-Resilient Certificate-based Key Encapsulation Scheme Resistant to Continual Leakage

In the past, the security of most public-key encryption or key encapsulation schemes is shown in an ideal model, where private keys, secret keys and random values are assumed to be absolutely secure to adversaries. However, this ideal model is not practical due to side-channel attacks in the sense that adversaries could gain partial information of these secret values involved in decryption operations by perceiving energy consumption or execution timing. In such a case, these schemes under the ideal model could suffer from side-channel attacks. Recently, leakage-resilient cryptography resistant to side-channel attacks is an emerging research topic. Certificate-based encryption (CBE) or certificate-based key encapsulation (CB-KE) schemes are a class of important public-key encryption. However, little work addresses the design of leakage-resilient CBE (LR-CBE) or leakage-resilient CB-KE (LR-CB-KE) schemes. In this paper, we present the first LR-CB-KE scheme with overall unbounded leakage property which permits adversaries to continuously gain partial information of the system secret key of a trusted certificate authority (CA), the private keys and certificates of users, and random values. In the generic bilinear group model, formal security analysis is made to prove that the proposed LR-CB-KE scheme is secure against chosen ciphertext attacks.

Secure Channel Free Certificate-Based Searchable Encryption Withstanding Outside and Inside Keyword Guessing Attacks

Searchable public key encryption (SPKE) is a useful public key cryptographic primitive that allows a user to perform keyword searches over publicly encrypted messages on an untrusted storage server while guaranteeing the privacy of the original messages as well as the search keywords. However, most of the previously proposed SPKE frameworks suffer from the security vulnerability caused by the keyword guessing attack and some other weaknesses. Inspired by the ideas of certificate-based cryptography and signcryption, we present a new SPKE framework called certificate-based searchable encryption. The new framework not only provides resistance to the existing known types of keyword guessing attacks, but also enjoys some appealing merits, such as implicit authentication, no key escrow and no secure channel. Under this new framework, we devise a concrete searchable certificate-based encryption scheme. In the random oracle model, it is proven to meet the keyword ciphertext indistinguishability, the keyword ciphertext unforgeability and the keyword trapdoor indistinguishability under the adaptive chosen-keyword attack. The comparisons indicate that it is secure and practicable.

Continuous Leakage-Resilient Certificate-Based Encryption Scheme Without Bilinear Pairings

Abstract Recently, much attention has been focused on designing provably secure cryptographic primitives in the presence of key leakage, even the continuous leakage attacks. However, several constructions on the (continuous) leakage-resilient certificate-based encryption (CBE) scheme were proposed based on the bilinear pairings, and the corresponding computational efficiency is lower. Also, the leakage on the master secret key is omitted in the previous constructions. In this paper, to further achieve the better performance, a new construction method of continuous leakage-resilient CBE scheme without bilinear pairings is proposed, and the chosen-ciphertext attacks security of designed scheme is proved based on the hardness of the classic decisional Diffie–Hellman assumption. The performance analysis shows that our method not only can obtain higher computational efficiency but also enjoys better security performances, such as the leakage parameter of secret key of user has the constant size, and an adversary cannot obtain any leakage on the secret key of user from the corresponding given ciphertext etc. The advantage is that our proposal allows leakage attacks of multiple keys, i.e. continuous leakage resilience of the secret key of user and bounded leakage resilience of the master secret key. Additionally, to provide the leakage resilience for the cloud computing, a novel data access control scheme for cloud storage service is proposed from our continuous leakage-resilient CBE scheme, which can keep its claimed security in the leakage seting.

Efficient certificate-based encryption and hierarchical certificate-based encryption schemes in the standard model

Efficient certificate-based encryption and hierarchical certificate-based encryption schemes in the standard model

Notes on a provably-secure certificate-based encryption against malicious CA attacks

Certificate-based encryption (CBE) is a very useful cryptographic primitive which not only simplifies the certificate management in traditional public-key encryption, but also solves the key escrow problem inherent in identity-based encryption. How to construct a provably-secure CBE scheme without using random oracles has been attracting the attentions of the research community. Recently, Lu et al. introduced a CBE scheme and claimed that their scheme is secure against adaptive chosen ciphertext attacks even considering a malicious certification authority (CA). In this paper, we demonstrate that a chosen ciphertext attacker can easily distinguish the challenge ciphertext generated by the challenger according to their security model. Further, the CA can trivially decrypt any entity’s ciphertext without knowing the entity’s secret key. In addition, we also point out that their security proof has some flaws and give a new CBE scheme secure against malicious CA attacks in the standard model.

Anonymous certificate-based broadcast encryption with constant decryption cost

Most of the existing broadcast encryption schemes are constructed in either public key cryptosystem or identity-based cryptosystem. However, the overload of certificate management is heavy for public key cryptosystem while the key escrow problem is inherent in identity-based cryptosystem. Certificate-based cryptosystem provides a promising solution of designing more efficient and secure broadcast encryption schemes. Meanwhile, it is an important security property to protect the privacy of receivers, anonymity in many broadcast encryption application scenarios. Furthermore, in the broadcast encryption applications with a large number of computationally constrained users, it is critical to lower the computation cost, especially the decryption cost of the users. In this paper, we first introduce the notion of anonymous certificate-based broadcast encryption. Specifically, we formalize the definition and security model for anonymous certificate-based broadcast encryption. Then we construct an anonymous certificate-based broadcast encryption scheme with constant decryption cost. Compared with the existing anonymous multi-receiver certificate-based encryption scheme, the proposed scheme has advantage in the computation efficiency. Therefore, our scheme is more feasible for those broadcast encryption application scenarios where there are many receivers with limited computation ability. In the respect of security, the proposed scheme achieves anonymity and confidentiality against adaptive chosen-ciphertext attacks simultaneously under standard assumption.

Provably secure certificate-based encryption with leakage resilience

The security of encryption schemes, in general, has been considered in an ideal environment, where the adversary cannot obtain the secret internal state of the scheme. However, in the real world, an adversary can gain partial information on the secret key through a key leakage attack. To avoid this attack, it is crucial to construct an encryption scheme with leakage resilience. In this paper, we first define a secure leakage-resilient model of certificate-based encryption. In this model, the adversary is permitted to get some information on the secret value through a side-channel attack. Moreover, we put forward a new leakage-resilient certificate-based encryption scheme. This scheme is secure against chosen ciphertext attack under the decisional 3-party Diffie–Hellman assumption in the standard model. Compared with the existing two certificate-based encryption schemes, our scheme enhances the security property, and the execution time of the proposed scheme is less than that of the two certificate-based encryption schemes.

Efficient certificate‐based encryption schemes without pairing

AbstractRecently, a lot of researches focused on identity‐based encryption (IBE). The advantage of this scheme is that it can reduce the cost of the public key infrastructure by simplifying certificate management. Although IBE has its own innovations, one of its weaknesses is the key escrow problem. That is, the private key generator in IBE knows decryption keys for all identities and consequently can decrypt any ciphertexts. The certificate‐based encryption (CBE) scheme proposed in EUROCRYPT 2003 provides a solution for the key escrow problem by allowing the certification authority to possess a partial decryption key that comprises the full decryption key together with the user‐generated private key. In this paper, we propose new CBE schemes without pairing and prove them to be Indistinguishability under Chosen Ciphertext Attack secure in the random oracle model based on the hardness of the computational Diffie–Hellman problem. When compared with other CBE schemes, our schemes are significantly efficient in terms of performance, which makes our schemes suitable for computation‐limited node (e.g., sensor, wearable device) networks. Copyright © 2016 John Wiley & Sons, Ltd.

A provably secure certificate-based encryption scheme against malicious CA attacks in the standard model

Certificate-based encryption (CBE) is a new public-key cryptographic paradigm that represents an interesting balance between conventional public-key encryption and identity-based encryption. It not only simplifies the certificate revocation problem in conventional public-key encryption, but also solves the key escrow problem inherent in identity-based encryption. In CBE, a certificate authority (CA) is employed to initialize the system and issue certificates for users. Each user needs both a private key and an up-to-date certificate to decrypt ciphertexts. In the previous concrete constructions of CBE, the CA is assumed to be honest-but-curious, that is, the CA always starts launching attacks only after it has initialized the system honestly. However, it seems that such an assumption does not necessarily reflect reality when we consider a malicious CA that is trying every effort to break the system. To show that the malicious CA attack exists in CBE, we present two concrete attacks against a previous CBE scheme. In both attacks, a malicious CA can easily break any user's confidentiality by implanting a trapdoor in the public system parameters. To fight against malicious CA attacks, we propose a new CBE scheme. The proposed CBE scheme is proven to be chosen-ciphertext secure against malicious CA attacks in the standard model. Performance comparison shows that it is efficient and practical.

Certificate-Based Signcryption Scheme without Pairing: Directly Verifying Signcrypted Messages Using a Public Key

To achieve confidentiality, integrity, authentication, and non-repudiation simultaneously, the concept of signcryption was introduced by combining encryption and a signature in a single scheme. Certificate-based encryption schemes are designed to resolve the key escrow problem of identity-based encryption, as well as to simplify the certificate management problem in traditional public key cryptosystems. In this paper, we propose a new certificate-based signcryption scheme that has been proved to be secure against adaptive chosen ciphertext attacks and existentially unforgeable against chosen-message attacks in the random oracle model. Our scheme is not based on pairing and thus is efficient and practical. Furthermore, it allows a signcrypted message to be immediately verified by the public key of the sender. This means that verification and decryption of the signcrypted message are decoupled. To the best of our knowledge, this is the first signcryption scheme without pairing to have this feature.

Continuous leakage-resilient certificate-based encryption

Encryption schemes are generally considered to be secure in an ideal environment, where the adversary cannot obtain the secret internal state of schemes. However, in the realistic environment, the adversary can gain partial information about decryption private key through various types of side channel attacks. In order to capture these attacks, it is crucial to design encryption schemes which are resilient to leakage. In this article, we first formalize a continuous leakage-resilient security model of certificate-based encryption. In the model, the adversary continuously obtains partial information about the secret states through the continuous leakage attacks. Furthermore, we construct a continuous leakage-resilient certificate-based encryption (CLR-CBE) scheme which is resilient to continuous leakage, and it is secure against adaptive chosen ciphertext attacks under the bilinear Diffie–Hellman inversion (BDHI) hardness assumption. Lastly, we show the bound on leakage and make comparison between proposed and existing schemes in terms of security properties and efficiency.

Sharing a Large Secret Image Using Meaningful Shadows Based on VQ and Inpainting

Certificate-based cryptography is a useful public key cryptographic primitive that combines the merits of traditional public key cryptography and identity-based cryptography. It not only solves the key escrow problem inherent in identity-based cryptography, but also simplifies the cumbersome certificate management problem in traditional public key cryptography. In this paper, by giving a concrete attack, we first show that the certificate-based encryption scheme without bilinear pairings proposed by Yao et al. does not achieve either the chosen-ciphertext security or the weaker chosen-plaintext security. To overcome the security weakness in Yao et al.’s scheme, we propose an enhanced certificate-based encryption scheme that does not use the bilinear pairings. In the random oracle model, we formally prove it to be chosen-ciphertext secure under the computational Diffie-Hellman assumption. The experimental results show that the proposed scheme enjoys obvious advantage in the computation efficiency compared with the previous certificate-based encryption schemes. Without costly pairing operations, it is suitable to be employed on the computation-limited or power-constrained devices.

Certificate-based encryption resilient to key leakage

Certificate-based encryption (CBE) is an important class of public key encryption but the existing schemes are secure only under the premise that the decryption key (or private key) and master secret key are absolutely secret. In fact, a lot of side channel attacks and cold boot attacks can leak secret information of a cryptographic system. In this case, the security of the cryptographic system is destroyed, so a new model called leakage-resilient (LR) cryptography is introduced to solve this problem. While some traditional public key encryption and identity-based encryption with resilient-leakage schemes have been constructed, as far as we know, there is no leakage-resilient scheme in certificate-based cryptosystems. This paper puts forward the first certificate-based encryption scheme which can resist not only the decryption key leakage but also the master secret key leakage. Based on composite order bilinear group assumption, the security of the scheme is proved by using dual system encryption. The relative leakage rate of key is close to 1/3.

Hierarchical Certificate-Based Encryption: Definition and an Efficient Construction

Certificate-based encryption is a new paradigm which was introduced by Gentry to address the complex public key revocation problem in traditional public key cryptosystems. It represents an interesting and potentially useful balance between traditional public-key encryption and identity-based encryption. In this paper, we introduce the notion of hierarchical certificate-based encryption that preserves the advantages of certificate-based encryption such as implicit certificate and key-escrow free while inheriting the properties of hierarchical identity-based encryption. We formalize the definition of hierarchical certificate-based encryption and also propose a concrete hierarchical certificate-based encryption scheme that is chosen-ciphertext secure under the hardness of bilinear Diffie-Hellman problem in the random oracle model.

A new certificate-based digital signature scheme in bilinear group

Certificate-based signature preserves advantages of implicit certification and no private key escrow as the certificate-based encryption scheme presented at Eurocrypt 2003 by Gentry. In this paper, we present a certificate-based signature scheme derived from bilinear pairings and prove its security in the random oracle model. The scheme is secure based on the traditional difficult problem defined in bilinear pairings. The efficiency is also presented to show the scheme is practical. Compared to earlier signatures with these properties, our scheme is efficient. Many other constructions could be derived by using this certificate-based signature in applications.

Certificate-Based Encryption Scheme without Pairing

Certificate-based cryptography is a new cryptographic primitive which eliminates the necessity of certificates in the traditional public key cryptography and simultaneously overcomes the inherent key escrow problem suffered in identity-based cryptography. However, to the best of our knowledge, all existed constructions of certificate-based encryption so far have to be based on the bilinear pairings. The pairing calculation is perceived to be expensive compared with normal operations such as modular exponentiations in finite fields. The costly pairing computation prevents it from wide application, especially for the computation limited wireless sensor networks. In order to improve efficiency, we propose a new certificate-based encryption scheme that does not depend on the pairing computation. Based on the decision Diffie-Hellman problem assumption, the schemes security is proved to be against the chosen ciphertext attack in the random oracle. Performance comparisons show that our scheme outperforms the existing schemes.

A Distributed Approach of a Threshold Certificate-Based Encryption Scheme with No Trusted Entities

ABSTRACT The distributed paradigm as manifested in distributed networks, calls for a different way from the traditional client-server model for providing Trusted third party (TTP) services to strengthen security. Certificate Authorities (CAs) are among the most common such TTP. Generating certified keys and manage certification information (the basic functionality of a CA) in a fully distributed manner is a key challenge in the distributed IT environment. Current approaches are based on the use of trusted entities within the distributed system that constitute single points of failure and follow complex certificate management and revocation mechanisms capable of hindering their adoption in a large scale. The hardware resources cost of each distributed system member committed to realizing and maintaining such certificate authority system can be high. Furthermore, distributed CA approaches lack flexibility when it come to dynamic member behavior such as dynamic member joining or leaving the system, since they employ complex, computational intensive mechanisms for retaining the CA consistency during such activity. In this paper, we propose the combination of a distributed key generation threshold cryptography scheme along with an efficient secure certificate-based encryption scheme to provide a solution that matches the above problems. The outcome of this proposal is a distributed Threshold Certificate-Based Encryption Scheme that has no need for any centralized trusted entity to create, and split secrets or distribute keys-certificates at any point during its operating cycle. The proposed scheme has few requirements concerning certificate management due to its inherited Certificate-based Encryption features which enables the scheme's participants to use their certificates as keys and has an easy participant addition-removal mechanism to support dynamic network environments. Extending the work done in (Fournaris, 2012), in this paper the proposed distributed Certificate Authority and encryption/decryption scheme is described and analyzed, participant addition and removal mechanisms as detailed and the scheme's security and performance is discussed. Performance characterization reveals that our scheme is very efficient in terms of computational intensive and resource constraining operations like Elliptic Curve point multiplication and bi-linear pairing.

Efficient and Generic Construction of Certification-Based Encryption in the Standard Model Based on the NIZK Proof System

Certificate-based encryption (CBE) is a new public key encryption paradigm which combines traditional PKI-based public-key encryption (PKE) and identity-based encryption (IBE) , and preserv es some of their most attractive features. CBE provides an efficient implicit certificate mechanism and allows a periodical update of certificate status . It eliminates third-party queries for the certificate status and simplifies the certificate revocation problem in the traditional PKI , while it solves the key escrow problem and the key distribution problem inherent in IBE. In this paper, we propose a new generic construction of CBE schemes from PKE and IBE, and prove it to be CCA-secure in the standard model. In our construction, we use an efficient one-time simulation-sound adaptive NIZK proof system as the security enhancing building block to guarantee the CCA-security of the generated CBE schemes . When compared to the previous method, the security requirements of the primitive encryption schemes in our construction are much weaker and the performance of the generated CBE schemes from our construction is much more efficient .