Decisional Bilinear Diffie-Hellman Research Articles

Public-Key Authenticated Encryption with Keyword Search Made Easy

Public-key searchable encryption allows keyword-associated tokens to be used to test if a ciphertext contains specific keywords. Due to the low entropies of keywords, the token holder can create ciphertexts from candidate keywords and test them using the token in hand to recover the keywords, known as inside keyword guessing attacks (IKGA). Public-key authenticated encryption with keyword search is a searchable encryption proposed to defend against such attacks. It ensures the sender's private key protects the ciphertexts from the IKGA. PAEKS schemes with reasonable security and practical efficiency remain elusive despite many proposals. This work provides a simple generic PAEKS scheme from non-interactive key exchange (NIKE) and symmetric-key equality-predicate encryption with three new constructions for the latter, respectively from pseudorandom functions (PRFs), the decision bilinear Diffie-Hellman assumption, and the learning-with-errors assumption. Instantiating our generic scheme, we derive several PAEKS schemes from the most well-known assumptions, with some of them achieving full cipher-keyword indistinguishability and full token indistinguishability in the standard model, for the first time. Our instantiated schemes allow practical implementations and outperform the existing PAEKS schemes under the same assumptions.

Public-Key Authenticated Encryption with Keyword Search Made Easy

Public-key searchable encryption allows keyword-associated tokens to be used to test if a ciphertext contains specific keywords. Due to the low entropies of keywords, the token holder can create ciphertexts from candidate keywords and test them using the token in hand to recover the keywords, known as inside keyword guessing attacks (IKGA). Public-key authenticated encryption with keyword search is a searchable encryption proposed to defend against such attacks. It ensures the sender's private key protects the ciphertexts from the IKGA. PAEKS schemes with reasonable security and practical efficiency remain elusive despite many proposals. This work provides a simple generic PAEKS scheme from non-interactive key exchange (NIKE) and symmetric-key equality-predicate encryption with three new constructions for the latter, respectively from pseudorandom functions (PRFs), the decision bilinear Diffie-Hellman assumption, and the learning-with-errors assumption. Instantiating our generic scheme, we derive several PAEKS schemes from the most well-known assumptions, with some of them achieving full cipher-keyword indistinguishability and full token indistinguishability in the standard model, for the first time. Our instantiated schemes allow practical implementations and outperform the existing PAEKS schemes under the same assumptions.

Unbounded non-zero inner product encryption

In a non-zero inner product encryption (NIPE) scheme, ciphertexts and keys are associated with vectors from an inner-product space. Decryption of a ciphertext for x→ is allowed by a key for y→ if and only if the inner product 〈x→,y→〉≠0. Existing constructions of NIPE assume the length of the vectors are fixed apriori. We present the first constructions of unbounded non-zero inner product encryption (UNIPE) with constant sized keys. Unbounded here refers to the size of vectors not being pre-fixed during setup. Both constructions, based on bilinear maps, are proven selectively secure under the decisional bilinear Diffie-Hellman (DBDH) assumption.Our constructions are obtained by transforming the unbounded inner product functional encryption (IPFE) schemes of Dufour-Sans and Pointcheval (ACNS 2019), one in the strict domain setting and the other in the permissive domain setting. Interestingly, in the latter case, we prove security from DBDH, a static assumption while the original IPFE scheme relied on an interactive parameterised assumption. In terms of efficiency, features of the IPFE constructions are retained after transformation to NIPE. Notably, the public key and decryption keys have constant size.

A lightweight attribute-based signcryption scheme based on cloud-fog assisted in smart healthcare.

In the environment of big data of the Internet of Things, smart healthcare is developed in combination with cloud computing. However, with the generation of massive data in smart healthcare systems and the need for real-time data processing, traditional cloud computing is no longer suitable for resources-constrained devices in the Internet of Things. In order to address this issue, we combine the advantages of fog computing and propose a cloud-fog assisted attribute-based signcryption for smart healthcare. In the constructed "cloud-fog-terminal" three-layer model, before the patient (data owner)signcryption, it first offloads some heavy computation burden to fog nodes and the doctor (data user) also outsources some complicated operations to fog nodes before unsigncryption by providing a blinded private key, which greatly reduces the calculation overhead of resource-constrained devices of patient and doctor, improves the calculation efficiency. Thus it implements a lightweight signcryption algorithm. Security analysis confirms that the proposed scheme achieves indistinguishability under chosen ciphertext attack and existential unforgeability under chosen message attack if the computational bilinear Diffie-Hellman problem and the decisional bilinear Diffie-Hellman problem holds. Furthermore, performance analysis demonstrates that our new scheme has less computational overhead for both doctors and patients, so it offers higher computational efficiency and is well-suited for application scenarios of smart healthcare.

Fine-Grained Forward Secure Firmware Update in Smart Home

Although the vigorous development of smart homes brings great convenience to people’s lives, smart homes usually suffer from various security threats due to firmware vulnerabilities. Firmware update is a possible solution, but existing methods cannot address the security issues during the update process well. To enable secure firmware updates, a Forward Secure Firmware Update (FSFU) system was realized based on the proposed Puncturable-Ciphertext Policy-Attribute-Based Encryption (P-CP-ABE) scheme. In FSFU, when the service provider delivers the latest firmware, it specifies an access policy and some tags to encrypt the data and appends its signature to achieve both fine-grained access control and authentication. Authorized customers can obtain the latest firmware by decrypting the encrypted data through their private key. In particular, after a successful update, each authorized customer can realize forward security by updating his/her puncturable key, which is an important private key component. In addition, FSFU is further enhanced by outsourcing a part of the parameters and computational tasks. Finally, FSFU was proven to be secure under the Decisional Bilinear Diffie–Hellman (DBDH) assumption. Our proposed FSFU is efficient from both the theoretical analysis and the experimental results.

Multiauthority Attribute-Based Encryption for Assuring Data Deletion

In order to alleviate key escrow issue, the notion of multiauthority attribute-based encryption (MA-ABE) was presented, which was widely applied in cloud storage environment. In data sharing environment, secure data deletion is very crucial and challenging issue. Hence, in this article, we concentrate on verification of data deletion operation, i.e., assuring data deletion. To solve this problem, we put forward a system model, formal definition and security model of MA-ABE for assuring data deletion. Furthermore, we design a MA-ABE scheme for assuring data deletion, which is more practicable than the single authority ABE scheme. The designed scheme not only overcomes key escrow issue, but also resists collusion attack between malicious user and unauthorized user. In addition, our scheme utilizes merkle hash tree to obtain verifiable data deletion. Based on decisional bilinear Diffie-Hellman (DBDH) assumption, the scheme is proven to be secure under the selective-policy model. The experimental result indicates that the designed scheme is efficient for practical application.

Attribute-based multi-user collaborative searchable encryption in COVID-19

With the outbreak of COVID-19, the government has been forced to collect a large amount of detailed information about patients in order to effectively curb the epidemic of the disease, including private data of patients. Searchable encryption is an essential technology for ciphertext retrieval in cloud computing environments, and many searchable encryption schemes are based on attributes to control user‘s search permissions to protect their data privacy. The existing attribute-based searchable encryption (ABSE) scheme can only implement the situation where the search permission of one person meets the search policy and does not support users to obtain the search permission through collaboration. In this paper, we proposed a new attribute-based collaborative searchable encryption scheme in multi-user setting (ABCSE-MU), which takes the access tree as the access policy and introduces the translation nodes to implement collaborative search. The cooperation can only be reached on the translation node and the flexibility of search permission is achieved on the premise of data security. ABCSE-MU scheme solves the problem that a single user has insufficient search permissions but still needs to search, making the user’s access policy more flexible. We use random blinding to ensure the confidentiality and security of the secret key, further prove that our scheme is secure under the Decisional Bilinear Diffie–Hellman (DBDH) assumption. Security analysis further shows that the scheme can ensure the confidentiality of data under chosen-keyword attacks and resist collusion attacks.

Outsourcing multiauthority access control revocation and computations over medical data to mobile cloud

With recent advances in cloud computing, mobile devices are increasingly being used to record patient physiological parameters, and transfer them to a cloud-based hospital information system, for access control mediation over a variety of stakeholders. In such a cloud-based architecture, the patient must specify an access policy for a group of authorized parties towards its outsourced data. Multiauthority ciphertext-policy attribute-based encryption (CP-ABE) was provided as an innovative cloud-based access control cryptographic primitive to tackle the key escrow issue in a centralized architecture, and boost flexibility through cross-domain attributes management. Existing works, however, still have glaring drawbacks. First, they still rely on a trusted authority to generate and distribute user secret keys. Second, they do not simultaneously provide encryption, decryption, or revocation outsourcing, resulting in high processing and communication cost for both the data sender and the data receiver. Third, they do not support both user and attribute revocation, and the integrity of ciphertext downloaded from the cloud is not always verified at the user end. As a result, this paper exploits the dummy attribute technique and introduces a novel, efficient, and secure multiauthority ciphertext-policy ABE method for mediating access control over medical data, in the mobile cloud. The ciphertext access policy enforcement, partial ciphertext decryption, and both the user and attribute indirect revocation updates are safely outsourced to the cloud server in this study. Theoretical analysis demonstrates that our scheme is efficient and verifiable, and we prove that our construction is secure under the decisional bilinear Diffie-Hellman assumption.

A novel insurance claim blockchain scheme based on zero-knowledge proof technology

It is crucial to ensure the privacy and authenticity of patients’ medical data in the medical insurance claim process, but in the current medical insurance claim process, there are some problems such as low efficiency, complex service, unreliable data and data leakage. Therefore, considering the privacy and sensitivity of patients’ medical data, we can improve the current issues by employing blockchain, smart contracts and zero-knowledge proof technology. In this paper, we propose a novel medical insurance claim scheme based on smart contracts, blockchain and zero-knowledge proof. Our scheme mainly involves two scenarios: medical insurance purchasing and medical insurance claiming. In the privacy-preserving transaction phases of the two scenarios, we can ensure the legitimacy and privacy of the transactions between the patients and the insurance companies by using a non-interactive zero-knowledge proof and the homomorphic encryption algorithm under the Decisional Bilinear Diffie–Hellman (DBDH) assumption. In the identity privacy-preserving phases of the two scenarios, we can ensure the legitimacy and the privacy of patients’ identities by integrating Schnorr protocol and Fiat–Shamir heuristic method. The security analysis, the computation cost and the communication cost of our scheme are given. Compared with our referred schemes, the performance evaluation shows that our scheme not only meets the requirements of the legality of the medical insurance claim, but also ensures the authenticity and privacy of the patients’ medical data. Moreover, the experimental results demonstrate that our scheme is feasible and has an acceptable time overhead.

Burn After Reading: Adaptively Secure Puncturable Identity-Based Proxy Re-Encryption Scheme for Securing Group Message

Puncturable proxy re-encryption (PPRE) is envisioned to provide secure access control delegation and fine-grained forward security for asynchronous group messaging systems. Nevertheless, the existing PPRE scheme not only suffers from the burden of certificate management but also merely achieves selective security based on the nonstandard assumption. In this article, a puncturable identity-based PRE (P-IB-PRE) scheme is proposed to efficiently protect the security and privacy of the group message. The proposed scheme introduces a message server as the proxy to transform ciphertext for each participant in the group; thus, the heavy computation overhead is delegated to the message server with abundant resources. Most importantly, our scheme enables the recipient to revoke its private key’s decryption capability of the specific messages without affecting other messages. Moreover, the identity-based mechanism eliminates the burden of certificate management as well as improves efficiency. The proposed scheme achieves adaptive security under the standard decisional bilinear Diffie–Hellman (DBDH) assumption. Eventually, theoretical and experimental analyses demonstrate that the proposed scheme has an excellent performance in efficiency and practicality.

An Improved ID-Based Data Storage Scheme for Fog-Enabled IoT Environments.

In a fog-enabled IoT environment, a fog node is regarded as the proxy between end users and cloud servers to reduce the latency of data transmission, so as to fulfill the requirement of more real-time applications. A data storage scheme utilizing fog computing architecture allows a user to share cloud data with other users via the assistance of fog nodes. In particular, a fog node obtaining a re-encryption key of the data owner is able to convert a cloud ciphertext into the one which is decryptable by another designated user. In such a scheme, a proxy should not learn any information about the plaintext during the transmission and re-encryption processes. In 2020, an ID-based data storage scheme utilizing anonymous key generation in fog computing was proposed by some researchers. Although their protocol is provably secure in a proof model of random oracles, we will point out that there are some security flaws inherited in their protocol. On the basis of their work, we further present an improved variant, which not only eliminates their security weaknesses, but also preserves the functionalities of anonymous key generation and user revocation mechanism. Additionally, under the Decisional Bilinear Diffie–Hellman (DBDH) assumption, we demonstrate that our enhanced construction is also provably secure in the security notion of IND-PrID-CPA.

Towards achieving efficient access control of medical data with both forward and backward secrecy

Healthcare service providers store the patients’ electronic medical records in the cloud in order to provide high quality healthcare services. Patients’ sensitive data is typically encrypted before storing in the cloud. However, it gives rise to a new challenge, namely access control over encrypted data. Attribute-Based Encryption (ABE) is a promising cryptographic technique to achieve the fine grained access control on outsourced encrypted data. Traditional ABE schemes assume a fixed access policy that is not suitable for the present dynamic environment. Although some ABE schemes with a dynamic access control policy have been proposed in the literature, these schemes have not addressed forward security, backward security, and user revocation after a policy update. In this paper, we propose an ABE scheme that supports access policy updates, and also provides forward security, backward security and user revocation at the same time. We have formally shown that the proposed scheme is Chosen Plaintext Attack (CPA)-secure under the Decisional Bilinear Diffie–Hellman (DBDH) assumption. Finally, the performance analysis exhibits that the proposed scheme is efficient in communication and computation, and is also suitable for resource constrained devices.

Self-Verifiable Attribute-Based Keyword Search Scheme for Distributed Data Storage in Fog Computing With Fast Decryption

Presently many searchable encryption schemes have been proposed for cloud and fog computing, which use fog nodes (or fog servers) to partly undertake some computational tasks. However, these related schemes still retain cloud servers to undertake most computational tasks, which result in large communication costs between edge devices and cloud servers. Therefore, in this paper we propose a self-verifiable attribute-based keyword search scheme for distributed data storage (SV-KSDS) in full fog computing, where each decryption operation on the data required by a user must meet the negotiated decryption rule between fog servers. Our SV-KSDS scheme first provides attribute-based distributed data storage among fog servers through the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(w, \sigma)$ </tex-math></inline-formula> threshold secret-sharing scheme, where fog servers can provide self-verifiable keyword search and data decryption for terminal users. Compared with the data storage in cloud computing, our scheme extends it to the distributed structure while providing fine-grained access control for distributed data storage through attribute-based encryption. The access control policy of our scheme is constructed on linear secret-sharing scheme, whose security is reduced to the decisional bilinear Diffie-Hellman assumption against chosen-keyword attack and the decisional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${q}$ </tex-math></inline-formula> -parallel bilinear Diffie-Hellman assumption against chosen-plaintext attack in the standard model. Based on theoretical analysis and practical testing, our SV-KSDS scheme generates less computation and communication costs, which further unloads some computational tasks from terminal users to fog servers so as to reduce computing costs of terminal users.

Verifiable online/offline multi-keyword search for cloud-assisted Industrial Internet of Things

Attribute-based encryption (ABE) and attribute-based keyword search (ABKS) facilitate fine-grained access and search control for cloud-assisted Industrial Internet of Things (IIoT). However, existing schemes suffer from the following drawbacks: (1) their computational overhead in data outsourcing and retrieval is exceptionally high; (2) they obtain wrong search results if one or more of the queried keywords are wrongly selected; (3) in most existing ABKS, the untrustworthiness of the cloud server is not taken into account, and the correctness of the search results is not verified; (4) existing verifiable ABKS schemes do not support search results verification without the main data, and verifiers have to first download the search results and then check their correctness. In this paper, we design a verifiable online/offline multi-keyword search (VMKS) scheme providing high-level solutions to the aforementioned problems. We use the healthcare setting as a case study, and we demonstrate how our VMKS can be deployed in cloud-assisted Healthcare IIoT (HealthIIoT). We prove the security of our VMKS in the standard model and under the hardness assumption of the decisional bilinear Diffie-Hellman (DBDH) problem. Empirical results demonstrate that our VMKS speeds up encryption and verification processes by more than 70% and 90%, respectively. Moreover, our scheme reduces the communication overhead in the verification phase by more than 80%.

An improved approach in CP-ABE with proxy re-encryption

A cryptographic encryption technique converts plaintext into ciphertext, which is non-recoverable by a malicious user without knowing the secret key. The Ciphertext Policy Attribute Based Encryption (CP-ABE) scheme aims for a multicast feature. Different users can decrypt the message if their secret key attributes match with the policy of attributes defined in the ciphertext. In literature, various approaches exist to enhance the naïve CP-ABE scheme. In 2021, Wang et al. proposed the proxy re-encryption-based CP-ABE scheme and presented that it is efficient as its predecessors. However, the proposed scheme follows the variable-length ciphertext where the ciphertext size depends on the number of attributes. Such variable-length ciphertext increases the required number of operations for the decryption, leading to the computation overhead at the receiver side. This paper proposes an enhanced CP-ABE-CL-PRE (CP-ABE Constant Length with PRE) scheme to provide the constant length ciphertext with proxy re-encryption. Our proposed scheme is secure under the Decisional Bilinear Diffie-Hellman (DBDH) problem.

An Enhanced Approach for CP-ABE with Proxy Re-encryption in IoT Paradigm

In Internet of Things (IoT), encryption is a technique in which plaintext is converted to ciphertext to make it non-recovered by the attacker without secret key. Ciphertext policy attribute based encryption (CP-ABE) is an encryption technique aimed at multicasting feature i.e. user can only decrypt the message if policy of attributes mentioned in ciphertext is satisfied by the user’s secret key attributes. In literature, the authors have improvised the existing technique to enhance the naïve CP-ABE scheme. Recently, in 2021, Wang et al. have proposed the CP-ABE scheme with proxy re-encryption and claimed it to be efficient as to its predecessors. However, it follows the variable length ciphertext in which size of ciphertext is increased with the number of attributes. Also, it leads to computation overhead on the receiver during decryption which will be performed by the IoT devices. Thus, in this paper we have proposed the improved scheme to provide the constant length ciphertext with proxy re-encryption to reduce the computation and communication time. The proposed scheme is secured under Decisional Bilinear Diffie-Hellman (DBDH) problem.

Towards Secure and Privacy-Preserving Data Sharing for COVID-19 Medical Records: A Blockchain-Empowered Approach

COVID-19 is currently a major global public health challenge. In the battle against the outbreak of COVID-19, how to manage and share the COVID-19 Electric Medical Records (CEMRs) safely and effectively in the world, prevent malicious users from tampering with CEMRs, and protect the privacy of patients are very worthy of attention. In particular, the semi-trusted medical cloud platform has become the primary means of hospital medical data management and information services. Security and privacy issues in the medical cloud platform are more prominent and should be addressed with priority. To address these issues, on the basis of ciphertext policy attribute-based encryption, we propose a blockchain-empowered security and privacy protection scheme with traceable and direct revocation for COVID-19 medical records. In this scheme, we perform the blockchain for uniform identity authentication and all public keys, revocation lists, etc are stored on a blockchain. The system manager server is responsible for generating the system parameters and publishes the private keys for the COVID-19 medical practitioners and users. The cloud service provider (CSP) stores the CEMRs and generates the intermediate decryption parameters using policy matching. The user can calculate the decryption key if the user has private keys and intermediate decrypt parameters. Only when attributes are satisfied access policy and the user's identity is out of the revocation list, the user can get the intermediate parameters by CSP. The malicious users may track according to the tracking list and can be directly revoked. The security analysis demonstrates that the proposed scheme is indicated to be safe under the Decision Bilinear Diffie-Hellman (DBDH) assumption and can resist many attacks. The simulation experiment demonstrates that the communication and storage overhead is less than other schemes in the public-private key generation, CEMRs encryption, and decryption stages. Besides, we also verify that the proposed scheme works well in the blockchain in terms of both throughput and delay.

Speech Encryption Scheme Based on Ciphertext Policy Hierarchical Attribute in Cloud Storage

In order to ensure the confidentiality and secure sharing of speech data, and to solve the problems of slow deployment of attribute encryption systems and fine-grained access control in cloud storage, a speech encryption scheme based on ciphertext policy hierarchical attributes was proposed. First, perform hierarchical processing of the attributes of the speech data to reflect the hierarchical structure and integrate the hierarchical access structure into a single-access structure. Second, use the attribute fast encryption framework to construct the attribute encryption scheme of the speech data, and use the integrated access to the speech data; thus, the structure is encrypted and uploaded to the cloud for storage and sharing. Finally, use the hardness of decisional bilinear Diffie–Hellman (DBDH) assumption to prove that the proposed scheme is secure in the random oracle model. The theoretical security analysis and experimental results show that the proposed scheme can achieve efficient and fine-grained access control and is secure and extensible.

Mercurial Signatures for Variable-Length Messages

Abstract Mercurial signatures are a useful building block for privacy-preserving schemes, such as anonymous credentials, delegatable anonymous credentials, and related applications. They allow a signature σ on a message m under a public key pk to be transformed into a signature σ′ on an equivalent message m′ under an equivalent public key pk′ for an appropriate notion of equivalence. For example, pk and pk′ may be unlinkable pseudonyms of the same user, and m and m′ may be unlinkable pseudonyms of a user to whom some capability is delegated. The only previously known construction of mercurial signatures suffers a severe limitation: in order to sign messages of length ℓ, the signer’s public key must also be of length ℓ. In this paper, we eliminate this restriction and provide an interactive signing protocol that admits messages of any length. We prove our scheme existentially unforgeable under chosen open message attacks (EUF-CoMA) under a variant of the asymmetric bilinear decisional Diffie-Hellman assumption (ABDDH).

A new construction of leakage-resilient CCA secure IBE scheme

Leakage of private information has become a threat to the security of cryptography systems. It has become a common security requirement that a cryptography scheme should withstand various leakage attacks. The non-interactive zero-knowledge (NIZK) argument system, one-time lossy filter (OT-LF) and one-time signature were widely used to create the generic constructions of leakage-resilient identity-based encryption (IBE) scheme with chosen-ciphertext attack (CCA) security. However, the computational efficiency of the corresponding generic construction is low because the underlying cryptographic tool is low. Thus, to solve the above problem, a new cryptographic primitive, called identity-based hash proof system with two encapsulated-key (T-IB-HPS), is proposed. The new generic constructions of leakage resilient IBE scheme with CCA security is created from the T-IB-HPS and message authentication code (MAC), and the security of the above proposed scheme is proved from the security of the underlying cryptographic tool. To further show the practicability, an instantiation of T-IB-HPS is constructed, and the formal security proof of the above instantiation is shown based on the decisional bilinear Diffie-Hellman (DBDH) assumption. Compared with the previous generic constructions of leakage resilient IBE scheme with CCA security, since the underlying cryptographic tools with low computational efficiency are not used, our generic construction has high computational efficiency.