Efficient Conditional Proxy Re-encryption with Chosen-Ciphertext Security

Recently, a variant of proxy re-encryption, named conditional proxy re-encryption (C-PRE), has been introduced. Compared with traditional proxy re-encryption, C-PRE enables the delegator to implement fine-grained delegation of decryption rights, and thus is more useful in many applications. In this paper, based on a careful observation on the existing definitions and security notions for C-PRE, we reformalize more rigorous definition and security notions for C-PRE. We further propose a more efficient C-PRE scheme, and prove its chosenciphertext security under the decisional bilinear Diffie-Hellman (DBDH) assumption in the random oracle model. In addition, we point out that a recent C-PRE scheme fails to achieve the chosen-ciphertext security

Strong identity-based proxy signature schemes, revisited

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Cryptanalysis of an online/offline certificateless signature scheme for Internet of Health Things

Recently, Khan et al. [An online-offline certificateless signature scheme for internet of health things,” Journal of Healthcare Engineering, vol. 2020] presented a new certificateless offline/online signature scheme for Internet of Health Things (IoHT) to fulfill the authenticity requirements of the resource-constrained environment of (IoHT) devices. The authors claimed that the newly proposed scheme is formally secured against Type-I adversary under the Random Oracle Model (ROM). Unfortunately, their scheme is insecure against adaptive chosen message attacks. It is demonstrated that an adversary can forge a valid signature on a message by replacing the public key. Furthermore, we performed a comparative analysis of the selective parameters including computation time, communication overhead, security, and formal proof by employing Evaluation based on Distance from Average Solution (EDAS). The analysis shows that the designed scheme of Khan et al. doesn’t have any sort of advantage over the previous schemes. Though, the authors utilized a lightweight hyperelliptic curve cryptosystem with a smaller key size of 80-bits. Finally, we give some suggestions on the construction of a concrete security scheme under ROM

mdTLS: How to Make middlebox-aware TLS more efficient?

The more data transmission over TLS protocol becomes increasingly common in IT Systems, the more middleboxes are deployed in networks. These middleboxes have several advantages, however, they become the target of cyber-attacks. Many researchers proposed revised versions of TLS protocols to make them secure, however, their approaches had some limitations. In this paper, we propose a middlebox-delegated TLS (mdTLS) protocol to improve performance based on the middlebox-aware TLS (maTLS), one of the most secure TLS protocols. We found out that the computational complexity of mdTLS is about twice as low as that of maTLS. Furthermore, we formally verified that our proposal meets newly defined security goals as well as those verified by maTLS. All of the formal models and lemmas are open to the public through following url https://github.com/HackProof/mdTLS.Comment: 22 pages, 3 figures, 9 table

The European Security Industry: A Research Agenda

The security industry can be defined, in the first instance, as the industry that produces the goods and services required to protect citizens from insecurity. Yet, this industry, as opposed to defence, has not been an area of intense research. Their boundaries are unclear and the industry is not well characterised. This paper analyses this knowledge gap and presents some ideas for a research agenda for this industry that could assist in unveiling the main features, the potential weaknesses and strengths, and the capability to solve the security needs of society in an efficient and effective way. The paper discusses a definition of this economic sector useful in setting its boundaries, and it briefly describes the main types of industries operating within the sector. It analyses methods for gathering information regarding the industry, customers, and other market agents. Finally, it outlines ways for assessing market performance in terms of the structure-conduct-performance paradigm.security industry, security market, terrorism and organised crime countermeasures, competition, market performance

Security analysis of two lightweight certificateless signature schemes

Certificateless cryptography can be considered as an intermediate solution to overcome the issues in traditional public key infrastructure (PKI) and identity-based public key cryptography (ID-PKC). There exist a vast number of certificateless signature (CLS) schemes in the literature; however, most of them are not efficient enough to be utilized in limited resources environments such as Internet of things (IoT) or Healthcare Wireless Sensor Networks (HWSN). Recently, two lightweight CLS schemes have been proposed by Karati et al. and Kumar et al. to be employed in IoT and HWSNs, respectively. While both schemes are claimed to be existentially unforgeable, in this paper, we show that both these signatures can easily be forged. More specifically, it is shown that 1) in Karati et al.\u27s scheme, a type 1 adversary, considered in certificateless cryptography, can generate a valid partial private key corresponding to any user of its choice and as a consequence, it can forge any users\u27 signature on any message of its choice, and 2) in Kumar et al.\u27s scheme, both types of adversaries which are considered in certificateless cryptography are able to forge any signer\u27s signature on an arbitrary message

Security Pitfalls of a Provably Secure Identity-based Multi-Proxy Signature Scheme

An identity-based multi-proxy signature is a type of proxy signatures in which the delegation of signing right is distributed among a number of proxy signers. In this type of cryptographic primitive, cooperation of all proxy signers in the proxy group generates the proxy signatures of roughly the same size as that of standard proxy signatures on behalf of the original signer, which is more efficient than transmitting individual proxy signatures. Since identity-based multi-proxy signatures are useful in distributed systems, grid computing, presenting a provably secure identity-based multi-proxy scheme is desired. In 2013, Sahu and Padhye proposed the first provably secure identity-based multi-proxy signature scheme in the random oracle model, and proved that their scheme is existential unforgeable against adaptive chosen message and identity attack. Unfortunately, in this paper, we show that their scheme is insecure. We present two forgery attacks on their scheme. Furthermore, their scheme is not resistant against proxy key exposure attack. As a consequence, there is no provably secure identity-based multi-proxy signature scheme secure against proxy key exposure attack to date

A Lattice-Based Identity-Based Proxy Blind Signature Scheme in the Standard Model

A proxy blind signature scheme is a special form of blind signature which allowed a designated person called proxy signer to sign on behalf of original signers without knowing the content of the message. It combines the advantages of proxy signature and blind signature. Up to date, most proxy blind signature schemes rely on hard number theory problems, discrete logarithm, and bilinear pairings. Unfortunately, the above underlying number theory problems will be solvable in the postquantum era. Lattice-based cryptography is enjoying great interest these days, due to implementation simplicity and provable security reductions. Moreover, lattice-based cryptography is believed to be hard even for quantum computers. In this paper, we present a new identity-based proxy blind signature scheme from lattices without random oracles. The new scheme is proven to be strongly unforgeable under the standard hardness assumption of the short integer solution problem (SIS) and the inhomogeneous small integer solution problem (ISIS). Furthermore, the secret key size and the signature length of our scheme are invariant and much shorter than those of the previous lattice-based proxy blind signature schemes. To the best of our knowledge, our construction is the first short lattice-based identity-based proxy blind signature scheme in the standard model