Established symmetric encryption schemes rely on short keys, with their length typically ranging between 128 and 256 bits. However, well-known physical key exchange schemes such as QKD (Quantum Key Distribution) and RKD (Radio-signal Key Distribution) generate megabits of new key material on a regular basis (i.e., daily, weekly, or otherwise). This article presents a new encryption scheme, OTPH, which is specifically designed to handle these megabits of regularly generated new key material. In this scheme, the key material is treated as a very long key, and its enormous entropy is fully exploited. OTPH first uses a bit selection procedure that randomly selects bits from the circularly arranged key, thereby extending the key many times over. From this, an HKDF (Hash Key Derivation Function) derives many new keys, and the result is a bit sequence that serves as the key for encryption using an XOR operation. OTPH uses only the XOR operation and hash function, which are also used in QKD and RKD during postprocessing (albeit with a different hash function). An initial cryptanalysis is also performed. OTPH operates in a manner entirely contrary to established methods, requiring a completely new perspective. It will not compete with AES, ChaCha20, etc., but instead be used primarily in the context of QKD and RKD.
Radio frequency identification (RFID) systems are increasingly used in applications such as supply-chain tracking, mobile commerce, pervasive computing, and smart healthcare. However, the highly constrained nature of RFID systems in dynamic and insecure environments creates significant challenges for designing authentication mechanisms that are both secure and efficient. In addition, Mobile RFID environments face strict constraints on energy, computation, and storage, making traditional security mechanisms unsuitable. To address these limitations, this work introduces a lightweight and secure authentication protocol tailored specifically for mobile RFID systems. The protocol leverages minimal cryptographic primitives, optimized message flows, and dynamic session parameters to reduce computational load, communication overhead, and energy consumption. At the same time, it ensures strong server-mediated authentication between mobile readers and RFID tags—with the back-end server acting as a trusted third party—and supports key-updating mechanisms that protect long-term privacy. The design mitigates a wide range of threats, including desynchronization attacks, replay attacks, and tag impersonation, while maintaining compatibility with the low-power hardware commonly found in RFID tags. The security validation of the proposed RFID authentication protocol was performed through both informal and formal analysis to provide comprehensive assurance of its resilience against potential attacks. Informal security analysis demonstrates that the proposed protocol achieves robust resistance to known attacks, preserves tag anonymity, and provides forward security—all without relying on heavy cryptographic operations. In order to validate these security properties, formal verification was conducted using Scyther and ProVerif, two widely recognized automated security verification tools. Performance evaluation further shows that the protocol outperforms existing schemes in terms of execution time, memory usage, and communication cost, making it a practical solution for real-world mobile RFID deployments.
Remote-access virtual private networks (VPNs) are a key component of enterprise security infrastructures. In practice, the effectiveness of a remote-access VPN is determined not only by cryptographic mechanisms but also by its ability to remain available and recover quickly under realistic operating conditions, which directly affects the operational security guarantees provided by the underlying cryptographic protocols. Enterprise deployments are characterized by heterogeneous client platforms, wireless access networks, and frequent endpoint and network disruptions. In this paper, we execute an exploratory case study of the operation of remote-access VPNs in enterprise environments through an empirical evaluation of WireGuard, OpenVPN, and IPsec. Using a controlled but realistic testbed with a cloud-hosted gateway and heterogeneous client platforms, we evaluate baseline performance as well as behavior under endpoint CPU stress, network impairments, MTU variation, and mobility-related disruptions, reflecting constrained and dynamically changing deployment conditions. The results suggest that VPN operational characteristics are influenced by both protocol design and execution environment. Within the evaluated deployment scenarios, kernel-based implementations generally exhibited higher resilience under endpoint resource contention and faster recovery after disruptions, while layered and virtualized environments exhibited increased variability and sensitivity to network imperfections. These findings underline that resilience in remote-access VPNs should be interpreted as a system-level property emerging from the interaction of implementation architecture, endpoint characteristics, and deployment conditions.
When smart tourism data are shared across scenic areas, hotels, transportation platforms, and regulatory authorities, existing access control schemes often struggle to simultaneously support batch authorization for data object sets, multi-authority collaboration, revocation-version binding, and low-latency online encryption. To address these challenges, this paper proposes a Threshold Distributed Batch Identity-Based Encryption scheme for object-level authorization of smart tourism data, termed TD-BIBE. The scheme jointly binds data object identities, batch labels, authorization periods, revocation versions, and authorization contexts to ciphertext access control. It employs Shamir secret sharing for threshold distributed key generation, preventing any single authorization authority from obtaining the complete master secret key. Set-polynomial digests and membership witnesses are used to support batch authorization over identity sets and object-level membership verification. A revocation-version binding mechanism restricts the validity scope of authorization materials, while an offline/online encryption structure reduces the online computational overhead of data providers. Formal security analyses are conducted in the random oracle model with respect to data confidentiality, object-level authorization, batch-label binding, revocation-version binding, resistance to unauthorized key-combination attacks, and threshold authorization security. Experimental results demonstrate that TD-BIBE is suitable for cross-departmental, multi-object, and on-demand data sharing in smart tourism scenarios.
Verifying a patient’s eligibility for insurance reimbursement typically requires disclosing sensitive clinical data—diagnosis codes, laboratory values, and policy details—to third parties, conflicting with the data-minimization principle of modern data-protection regimes. Blockchain platforms improve auditability but, when health records are placed on-chain, amplify the privacy problem. This paper presents a zero-knowledge framework in which a patient proves that an authority-signed health record satisfies a set of policy predicates—a covered diagnosis, a laboratory value within an approved range, and a claim amount within the policy ceiling—without revealing the underlying values. Records are committed to an on-chain Merkle registry, and a record-bound nullifier prevents double claims without linking a claim to the patient. We state the NP relation proved by the circuit and reduce claim soundness, claim unlinkability, and front-running resistance to the knowledge soundness and zero-knowledge of the argument, the collision resistance of the hash, and the unforgeability of the signature scheme. A circom and snarkjs prototype with a Solidity verifier compiles to 10,050 R1CS constraints, of which the eligibility predicates contribute only 2.1%, and produces a constant 256-byte proof verified on-chain by a fixed four-pair check. On-chain cost scales with the number of public inputs rather than circuit size, and we identify the attack surface such designs commonly leave open—proof front-running, issuer-side linkability, and anonymity-set size, which the registry population bounds rather than tree depth.
