Most recently, Wang et al. proposed (in IEEE TCC, doi: 10.1109/TCC.2024.3461732) a lightweight privacy-preserving ciphertext retrieval scheme based on edge computing (termed as LPCR) by combining ciphertext policy attribute-based encryption and searchable encryption techniques. The authors claimed that LPCR can achieve the security of chosen plaintext attack (CPA) and chosen keyword attack (CKA), and resist collusion attack. However, by presenting a concrete plaintext recovery attack (PRA), we demonstrate that every decryption key has the ability to decrypt any user's ciphertext and get the plaintext document encrypted in it. Next, using PRA, we illustrate that LPCR is vulnerable to CPA, CKA and collusion attacks.

Internet-of-Drones (IoD) is an emerging network connecting various physical devices, namely drones, flying area station servers (FASs), controlling authority and cloud, through the Internet to capture and share data with the intended data users. Outsourcing the data collected by drones to a cloud raises data confidentiality and security issues. The privacy of drone data can be realized by keeping it encrypted form, but it affects flexibility and usability in terms of searching and retrieving encrypted data. Hence, to facilitate the difficulty of working on encrypted data and protect the drone data, we propose a secure Data Storage and Retrieval Scheme in a cloud-assisted Internet-of-Drones environment (DSRS-IoD), which is a novel secure hybrid attribute-based searchable encryption with outsourced decryption and verifiable data retrieval mechanism. In the DSRS-IoD framework, a drone transmits the captured data to its FAS using the identity-based encryption mechanism, next the FAS outsources the received drone data to the cloud employing attribute-based searchable encryption framework, and a data user can securely retrieve the required data from the cloud by leveraging keyword search functionality. Our DSRS-IoD scheme simultaneously supports (i) fine-grained access control, (ii) data storage and retrieval services, (iii) data integrity, (iv) search results self-verifiability, (v) keyword privacy, and (vi) lightweight decryption cost. We present formal security models and provide security proofs for our proposed scheme. The experimental results demonstrate that the scheme is practical.

Storing and sharing confidential data in a public cloud storage system always raises privacy and security issues. When data is outsourced to a cloud server, the basic demands are secure and authenticated data storage, fine-grained data access control, secure search for the outsourced data, and search results verification. Attribute-Based Signcryption (ABSC) is a promising public-key cryptosystem for accomplishing data confidentiality and authenticity together. However, incorporating verifiable Boolean formula based keyword search and verifiable outsourced unsigncryption mechanisms into an ABSC is quite challenging. This is because the data user should be able to check whether the search result, returned by the untrusted cloud, has been correctly created. Precisely, the data user should be able to verify the correctness of the search, transform and signature verification operations involved in generating the search result. In this paper, for the first time, we propose a secure Searchable Attribute-Based Signcryption (sABSC) scheme that simultaneously supports (i) Boolean formula search over signcrypted data, (ii) keyword privacy, (iii) verifiable outsourced unsigncryption, and (iv) search results self-verifiability. In sABSC, each data user can efficiently verify the correctness of the search results returned by the cloud without interacting with any authority. We define more general security definitions of sABSC and provide rigorous security analysis. Performance evaluation exhibits that the proposed sABSC is practical.

Attribute‐based signature (ABS) schemes play a vital role to accomplish authentication and signer privacy simultaneously. In recent years, cryptographic primitives are deployed on insecure devices such as mobile devices; thereby, secret key exposure seems inevitable. To alleviate the impact of key exposure in ABS scenarios, the authors apply the method of key insulation to ABS and construct the first signature‐policy attribute‐based key‐insulated signature (ABKIS) scheme. The proposed construction supports expressive monotone Boolean functions as signing predicates and preserves signer privacy. Their ABKIS scheme is key‐insulated and strong key‐insulated secure under computational Diffie–Hellman exponent assumption. To the best of their knowledge, the proposed ABKIS is the first ABS scheme in signature‐policy flavour dealing with key exposure problems employing key‐insulation mechanism.

Abstract The functionality of ciphertext‐policy attribute‐based encryption (CP‐ABE) enables the encryptor to encrypt the data for a group of users of his choice by incorporating an access policy over target receivers' attributes into encryption algorithm itself. This makes CP‐ABE systems appealing in several applications where complex access control is at prime concern, but incurs high communication and computation overheads which could impede its practical usage. Another limitation of CP‐ABE is that the ciphertext includes the access policy explicitly and, hence, anyone who has access to the ciphertext can identify all legitimate recipients of that ciphertext. This is not desirable for certain mission‐critical applications such as military operations. In order to alleviate these problems, we add privacy‐preserving property efficiently to CP‐ABE scheme via concealing the access policy partially. The encryption in our construction exploits monotone access policies over receivers' attributes and makes ciphertext size constant. The construction is fully secure and can achieve recipient anonymity as the ciphertext terms do not leak any information about recipients. The full semantic security with anonymity relies on dual‐system encryption technique in composite order bilinear groups. To the best of our knowledge, the proposed scheme is thefirstconstruction in the anonymous ABE literature with the stated functionality. Copyright © 2015 John Wiley & Sons, Ltd.