Identity-based broadcast encryption for multi-privileged groups using Chinese remainder theorem

The attribute-based encryption (ABE) scheme with monotonic access structure cannot deal with an access structure that is associated with the negation of attributes, which is not convenient for real world applications. In this paper, we attempt to propose a more expressive non-monotonic ABE scheme through a new method. To achieve this goal, we firstly propose a linear two-mode identity-based broadcast encryption (TIBBE) scheme based on an identity-based broadcast encryption (IBBE) scheme. We introduce the concept of identity-based revocation (IBR) for this scheme without increasing the size of parameters in IBBE. The scheme is selective identity secure under the m-DBDHE assumption. Then, we convert the TIBBE scheme into a non-monotonic key-policy attribute-based encryption (KP-ABE) scheme with compact parameters. Our KP-ABE scheme could achieve constant-size ciphertexts, and the scale of the private keys grows linearly with the scale of the attribute set. Besides, the computational cost is the lowest compared with other existing non-monotonic KP-ABE schemes.

In this paper, we propose a generic construction of forward-secure identity-based encryption. We first introduce a relaxed variant of hierarchical identity-based encryption called identity-based binary tree encryption and construct a concrete identity-based binary tree encryption scheme which is provably secure in the standard model. We then show that forward-secure identity-based encryption can be generically constructed from identity-based binary tree encryption. Based on the proposed identity-based binary tree encryption scheme, we obtain a direct chosen-ciphertext secure forward-secure identity-based encryption scheme without random oracles.

Identity-based proxy re-encryption version 2: Making mobile access easy in cloud

Middle-product learning with errors (MP-LWE) was recently introduced by Rosca, Sakzad, Steinfeld and Stehlé (CRYPTO 2017) as a way to combine the efficiency of Ring-LWE with the more robust security guarantees of plain LWE. While Ring-LWE is at the heart of efficient lattice-based cryptosystems, it involves the choice of an underlying ring which is essentially arbitrary. In other words, the effect of this choice on the security of Ring-LWE is poorly understood. On the other hand, Rosca et al. showed that a new LWE variant, called MP-LWE, is as secure as Polynomial-LWE (another variant of Ring-LWE) over any of a broad class of number fields. They also demonstrated the usefulness of MP-LWE by constructing an MP-LWE based public-key encryption scheme whose efficiency is comparable to Ring-LWE based public-key encryption. In this work, we take this line of research further by showing how to construct Identity-Based Encryption (IBE) schemes that are secure under a variant of the MP-LWE assumption. Our IBE schemes match the efficiency of Ring-LWE based IBE, including a scheme in the random oracle model with keys and ciphertexts of size $$\tilde{O}(n)$$ (for n-bit identities). We construct our IBE scheme following the lattice trapdoors paradigm of [Gentry, Peikert, and Vaikuntanathan, STOC’08]; our main technical contributions are introducing a new leftover hash lemma and instantiating a new variant of lattice trapdoors compatible with MP-LWE. This work demonstrates that the efficiency/security tradeoff gains of MP-LWE can be extended beyond public-key encryption to more complex lattice-based primitives.

Identity Based Encryption (IBE) has emerged as a solution to the problem of trust in public keys of Public Key Cryptography (PKC) systems where most of the proposed IBE schemes are based on bilinear pairing and Elliptic Curve Cryptography. The heavy computations involved in such schemes make pairing based schemes less practical. Efficient non-pairing schemes have been designed over the famous RSA structure to bridge the practical gap between actual public key ciphers and utility of IBE in it. Yet the security threats to RSA have been retained in such proposals. This paper presents an RSA based IBE scheme which overcomes the security problems of RSA and has linear computations involved and makes key management/revocation easy.

The first practical identity based encryption (IBE) scheme was published by Boneh and Franklin at Crypto 2001, based on the elliptic curve pairing. Since that time, many other IBE schemes have been...

By a generic transformation by Canetti, Halevi, and Katz (CHK) every Identity-based encryption (IBE) scheme implies a chosen-ciphertext secure public-key encryption (PKE) scheme. In the same work it is claimed that this transformation maps the two existing IBE schemes to two new and different chosen-ciphertext secure encryption schemes, each with individual advantages over the other.In this work we reconsider one of the two specific instantiations of the CHK transformation (when applied to the “second Boneh/Boyen IBE scheme”). We demonstrate that by applying further simplifications the resulting scheme can be proven secure under a weaker assumption than the underlying IBE scheme.Surprisingly, our simplified scheme nearly converges to a recent encryption scheme due to Boyen, Mei, and Waters which itself was obtained from the other specific instantiation of the CHK transformation (when applied to the “first Boneh/Boyen IBE scheme”). We find this particularly interesting since the two underlying IBE schemes are completely different.The bottom line of this paper is that the claim made by Canetti, Halevi, and Katz needs to be reformulated to: the CHK transformation maps the two known IBE schemes to nearly one single encryption scheme.KeywordsEncryption SchemeMessage Authentication CodeChallenge CiphertextChoose Ciphertext AttackBilinear GroupThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A new approach to identity-based encryption (IBE), called identity-based factors selection (IBFS), allows to build efficient and fully collusion-resistant IBE schemes without the need for pairings or the use of lattices. The security of these constructions (in the random oracle model) rests on the hardness of a new problem which combines the computational Diffie-Hellman problem with the fact that linear equation systems with more variables than given equations do not have unambiguous solutions. The computational efficiency of the resulting IBE schemes is (for values of the security parameter not smaller than 80) better than in previous IBE schemes. The construction of these schemes may be seen as an extension of the ElGamal public-key encryption scheme. The sender of a message computes the ElGamal-like public key of the message receiver by first selecting, uniquely determined by the identity of the receiver, from a set of group elements \(\{g^{e_1}, ..., g^{e_z} \}\) made available as public parameters a subset, and then multiplying the selected elements.KeywordsIdentity-based encryptionIBEIdentity-based key-encapsul- ation mechanismID-KEMIdentity-based factors selectionIBFS

Due to the enormous growth in the amount of digital information that needs to be stored, outsourcing data to third-party storage service providers, such as cloud, have attracted much attention in recent times. This has raised significant security issues such as how to control access to outsourced data stored on third-party sites. There have been many works on access control in the literature, and one of the well-known access control models is the role-based access control (RBAC), which provides flexible control and management by having two level mappings, users to roles and roles to privileges on data objects. Several cryptographic RBAC schemes have been proposed which integrate cryptographic techniques with RBAC models to enforce RBAC policies. In this paper, we develop the first generic constructions for cryptographic RBAC schemes which we refer to as role-based encryption (RBE) schemes. A RBE scheme allows data to be encrypted in such a way that only users with specific roles can decrypt the data. Hence, it can be used to enforce RBAC policies in an outsourcing environment. Our constructions use ID-based broadcast encryption (IBBE) techniques to build RBE schemes, and we show that the RBE scheme built from our generic constructions is secure if the selected IBBE scheme is secure. We also compare these constructions and analyse the advantages and disadvantages of each construction type.

In this paper we propose an identity(ID)-based signature scheme using gap Diffie-Hellman (GDH) groups. Our scheme is proved secure against existential forgery on adaptively chosen message and ID attack under the random oracle model. Using GDH groups obtained from bilinear pairings, as a special case of our scheme, we obtain an ID-based signature scheme that shares the same system parameters with the IDbased encryption scheme (BF-IBE) by Boneh and Franklin [BF01], and is as efficient as the BF-IBE. Combining our signature scheme with the BF-IBE yields a complete solution of an ID-based public key system. It can be an alternative for certificate-based public key infrastructures, especially when efficient key management and moderate security are required.

We present IND-ID-CPA secure identity-based encryption (IBE) schemes with tight reductions to the bilinear Diffie-Hellman (BDH) problem. Since the methods for obtaining IND-ID-CCA secure schemes from IND-ID-CPA secure schemes with tight reductions are already known, we can consequently obtain IND-ID-CCA secure schemes with tight reductions to the BDH problem. Our constructions are based on IBE schemes with tight reductions to the list bilinear Diffie-Hellman (LBDH) problem, and the schemes are converted to those with tight reductions to the BDH problem. Interestingly, it can be shown that there exists a black box construction, in which the former IBE schemes are given as black boxes. Our constructions are very simple and reasonably efficient.

<p style='text-indent:20px;'><b>I</b>dentity-<b>B</b>ased <b>B</b>roadcast <b>E</b>ncryption (<inline-formula><tex-math id="M1">\begin{document}$\textsf{IBBE}$\end{document}</tex-math></inline-formula>) is a novel concept that can efficiently and securely transmit confidential content to a group of authorized users without the traditional <b>P</b>ublic-<b>K</b>ey <b>I</b>nfrastructure (<inline-formula><tex-math id="M2">\begin{document}$\textsf{PKI}$\end{document}</tex-math></inline-formula>). After carefully exploring these areas, we have observed that none of the existing works have adopted the quantum-attack resistant cryptographic machinery <b>M</b>ultivariate <b>P</b>ublic-<b>K</b>ey <b>C</b>ryptography (<inline-formula><tex-math id="M3">\begin{document}$\textsf{MPKC}$\end{document}</tex-math></inline-formula>) with provable security. We are the <i>first</i> to design a quantum-safe <inline-formula><tex-math id="M4">\begin{document}$\textsf{IBBE}$\end{document}</tex-math></inline-formula> that solely relies on the <inline-formula><tex-math id="M5">\begin{document}$\textsf{MPKC}$\end{document}</tex-math></inline-formula> framework. Our proposed protocol has achieved <inline-formula><tex-math id="M6">\begin{document}$ \mathcal{O}(n) $\end{document}</tex-math></inline-formula>-size communication bandwidth and <inline-formula><tex-math id="M7">\begin{document}$ {n^3}\cdot\mathcal{O}\big(\max\big\{N, {\delta}^4\big\}\big) $\end{document}</tex-math></inline-formula>-size overhead storage without any security breach. Here, <inline-formula><tex-math id="M8">\begin{document}$ n $\end{document}</tex-math></inline-formula> is the number of variables for each multivariate polynomial, <inline-formula><tex-math id="M9">\begin{document}$ N $\end{document}</tex-math></inline-formula> represents the total number of system users, and <inline-formula><tex-math id="M10">\begin{document}$ \delta $\end{document}</tex-math></inline-formula> denotes a positive fixed-length. More positively, our design has achieved the <i>adaptive</i> <b>IND</b>istinguishable <b>C</b>hosen-<b>C</b>iphertext <b>A</b>ttack (<inline-formula><tex-math id="M11">\begin{document}$\textsf{IND-CCA}$\end{document}</tex-math></inline-formula>) security in the <b>R</b>andom <b>O</b>racle <b>M</b>odel (<inline-formula><tex-math id="M12">\begin{document}$\textsf{ROM}$\end{document}</tex-math></inline-formula>) under the hardness of standard <b>M</b>ultivariate <b>Q</b>uadratic (<inline-formula><tex-math id="M13">\begin{document}$\textsf{MQ}$\end{document}</tex-math></inline-formula>) problem. We emphasize that our system can also be immune against collusion attacks where several users come together to create an illicit decryption box.</p>

Instant Messaging (IM) services over the last few years have evolved from a casual communication tool to a formal business communication tool. Security requirements change drastically when instant messaging systems are employed in the corporate world as sensitive data needs to be transmitted. Many security enhancements have been proposed for instant messaging from the perspective of peer-to-peer talk. In this paper, we study the extension of secure instant messaging for group settings. We also propose a scheme, IBECRT, which uses ID-based encryption and the Chinese Remainder Theorem. The scheme does not require a central trusted entity for key distribution and achieves uniform work-load distribution. Additionally, the protocol has the following properties: hiding the users’ identity in a conference, authentication of senders, and integrity protection of the messages exchanged.

At Eurocrypt 2005, Waters presented an identity based encryption (IBE) protocol which is secure in the full model without random oracle. In this paper, we extend Waters' IBE protocol to a hierarchical IBE (HIBE) protocol which is secure in the full model without random oracle. The only previous construction in the same setting is due to Waters. Our construction improves upon Waters' HIBE by significantly reducing the number of public parameters.

The Fujisaki-Okamoto (FO) conversion is a generic conversion to enhance a public key encryption scheme with security of one-way against chosen plaintext attacks (OW-CPA) to security of indistinguishable against adaptive chosen ciphertext attacks (IND-CCA) in the random oracle model. Existing works have shown that the FO conversion also can generically upgrade the security of the identity-based encryption (IBE) schemes or certificateless public key encryption (CL-PKE) schemes. However, it is still unknown if the same holds for certificate-based encryption (CBE) schemes. In this paper, we investigate the generic security of the CBE scheme obtained by applying the FO conversion to an arbitrary underlying OW-CBE-CPA secure CBE scheme and confirm that the FO conversion can generically convert any OW-CBE-CPA secure CBE into an IND-CBE-CCA secure CBE. We also note that the straightforward application of the FO conversion only leads to a CBE scheme with a loose reduction. To solve this problem, we propose an enhanced FO conversion which just introduces minor extra computation overhead, but results in considerably more efficient security reduction.