Certificateless Cryptosystems Research Articles

A lattice-based efficient heterogeneous signcryption scheme for secure network communications

Ensuring the security of transmitted content is an important task in network communication. Signcryption technology combines signature and encryption operations in a single step to achieve message authentication and confidentiality. In practical applications, users are usually in different cryptographic systems, the ordinary signcryption technology cannot realize communication between two different cryptographic systems. And the ciphertext structure of the existing signcryption schemes is relatively complex, signcryption is not efficient. Therefore, in order to solve the problem of efficient communication between different cryptosystems and ensure quantum security, this paper proposes a lattice-based efficient heterogeneous signcryption scheme for secure network communications. This signcryption scheme accomplishes signcryption through matrix operations and hash functions, which avoids complex signcryption structures, efficiently realizes bidirectional message communication between identity-based cryptosystems and certificateless cryptosystems.

Escrow-Less Identity-Based Signature Scheme with Outsourced Protection in Cloud Computing

The identity-based cryptosystem (IBC) outfits with the most beneficial key management procedures. The IBC is bounded to the small network system due to the internal key escrow problem, which leads to two other problems: key abusing and user slandering problems. Some solutions that address the key escrow problem are certificate-less cryptosystems and multiple authorities-based IBC. However, they are expensive in terms of computation or loss of the identity-based feature. This paper presents an escrow-less identity-based signature (EL-IBS) scheme, where we employ one key generation center that authenticates a user and many authorities that issue a protected private key share without user authentication. We also outsource the key protection overhead to the cloud privacy centers. We proved that the our EL-IBS scheme is existential unforgeable, key abusing and existential user slandering secured against adaptively chosen message attack under the random oracle model and the well-known computational Diffie–Hellman problem.

CCA-Secure and Revocable Certificateless Encryption with Ciphertext Evolution

Certificateless cryptosystems have attracted great interests in cryptographic research since its invention. Because compared with traditional public key cryptosystems or identity-based cryptosystems, they could not only simplify the certificate management, but also alleviate the key escrow problem. In certificateless cryptosystems, user revocation is a challenging issue. To address this issue, one popular method is to update the key via public channels. However, most of the existing schemes in this approach are impractical because of the following two shortcomings. Firstly, the user needs to maintain a list of decryption keys, but the size of the list will keep increasing. Secondly, the revoked user can still recover the plaintexts of the encrypted data prior to revocation, and this is a particular threat in some applications. To solve these problems, this paper presents revocable certificateless encryption with ciphertext evolution. We give a generic construction and then describe how it can be initialized concretely. In our proposed scheme, the user only needs to keep one decryption key, and once a user is revoked, it can no longer decrypt any ciphertext in the server. Moreover, the IND-CCA security model is defined against three types of attacks. And our schemes are formally proved to satisfy these security requirements.

Cryptanalysis of Two Signature Schemes for IoT-Based Mobile Payments and Healthcare Wireless Medical Sensor Networks

Certificateless cryptography does not require any certificate for the public key authentication and users' public keys are transmitted with ciphertext/signatures or by making them available in the IoT-based public directory in a proper way. Due to these features, certificateless cryptosystems are considered as fundamental cryptographic buildingblocks to provide authenticity, integrity and non-repudiation suitable for IoT applications. Yeh proposed a transaction scheme based on a certificateless signature scheme for IoT-based mobile payments implementing on Android Pay. He showed that the CLS scheme was unforgeable against Type I and Type II adversaries under the intractability of the mathematical problem. Despite the security proofs, we show that Yeh's scheme is still insecure against both Type I and Type II adversaries. Recently, Gayathri et al. constructed a compact certificateless aggregate signature scheme for Healthcare Wireless Medical Sensor Networks. Their aggregate signatures are constant-size independent of the number of signers. In this paper, we show that anyone can forge certificateless aggregate signatures of their scheme on any sets of messages and identities from only publicly known information, i.e. their scheme is entirely broken. We then discuss some improvements.

Certificateless Deniable Authenticated Encryption for Location-Based Privacy Protection

Deniable authenticated encryption (DAE) is a cryptographic primitive that supports data confidentiality with deniable authentication in an efficient manner. The DAE plays a significant role in location-based service systems for privacy protection. In this paper, we construct a certificateless DAE (CLDAE) scheme. The CLDAE is based on certificateless cryptosystems (CLCs), which avoids the need to manage public key certificates in public key infrastructure (PKI)-based cryptosystems and key escrow problems in identity-based cryptosystems (IBCs). Our design utilizes hybrid methods: tag-key encapsulation mechanism (TKEM) and data encapsulation mechanism (DEM). This technique is more suitable for location-based applications. We show how to construct a CLDAE scheme utilizing a certificateless deniable authenticated tag-KEM (CLDATK) and a DEM. We also design a CLDATK scheme and provide formal security proof using the random oracle model (ROM). We conduct a comprehensive performance analysis, which shows that CLDAE is highly efficient in terms of communication overhead. We also provide an application of the CLDAE for a location-based service (LBS) system.

A certificateless signature scheme and a certificateless public auditing scheme with authority trust level 3+

Many certificateless cryptosystems have been proposed for cloud security applications. These applications have to face the inherent issues of dealing with low authority trust levels, especially when the cloud server takes charge of doing the role of the key generation center (KGC), that is the authority to trust. This paper focuses on popular authority trust problems in certificateless signatures and proposes a public cloud auditing scheme with high trust level. In current cloud security applications based on certificateless cryptography, the level of trust can at most detect and prove that the authority is guilty but can never punish it for its malicious behavior; precisely, in those settings where malicious servers have to be punished, an external arbitrator becomes necessary. We develop a novel notion of enhanced authority trust level, that we call 3+, where even if KGCs can impersonate any entity, still there is no way to avoid an immediate penalty for its malicious behavior. First, we construct a certificateless signature scheme with authority trust level 3+, then we prove its security in the random oracle model, illustrating some benefits in applications made for clouds. In particular, we propose a certificateless homomorphic authenticable signature scheme and a cloud public auditing scheme. Our proposed trust level 3+ sensibly boosts the trustworthiness and acceptability of such cloud computation environments by its ordinary customers.

Security analysis of certificateless proxy signature scheme

Certificateless cryptography eliminates the need of certificates in the Public Key Infrastructure (PKI) and solves the inherent key escrow problem. Recently,Fan Rui et al. proposed a certificateless proxy signature scheme based on a certificateless signature scheme. They claimed that their scheme satisfied the security requirements of certificateless proxy signature schemes. However,the analysis of their scheme showed that it was insecure against the two kinds of attacks in certificateless cryptosystems,i.e. public key replacement attacks and malicious Key Generating Centre (KGC) attacks. The attack methods and the defensive measures were presented.