IoMT enables continuous monitoring through connected medical devices, producing real-time health data that must be protected from unauthorised access and tampering. Blockchain ensures this security with its decentralised, tamper-resistant, and access-controlled ledger. A critical challenge arises when patients are unconscious, making timely access to their IoMT data essential for emergency treatment. To address this, we have created and designed a novel Threshold Proxy Re-Encryption+ (TPRE+) framework that integrates threshold cryptography with unidirectional, non-transitive proxy re-encryption(PRE) with Shamir’s secret sharing to distribute re-encryption capabilities among multiple proxies, reducing single-point failure and collision risks. Our contributions are threefold: (i) We first proposed a semantically secure TPRE+ scheme with Shamir-secret sharing, (ii) Construction of an IND-CCA secure TPRE+ scheme, and (iii) Development of a secure, distributed medical record storage system for unconscious patients, combining blockchain infrastructure, IPFS-based encrypted storage, and our proposed TPRE+ schemes. This integration ensures confidentiality, integrity, and fault-tolerant access to critical patient data, enabling secure and efficient deployment in real-world emergency healthcare scenarios.

Abstract Secure exchange of data among the various stake holders of healthcare systems is of prime importance. As the size of the healthcare networks grew, several variants of Public Key Infrastructures (PKIs) were proposed as a means to achieve reliable authentication, confidentiality, non-repudiation, etc. The most prevalent approach to PKI has been the use of Certificate Authorities (CAs). But, events like the breach of the CA DigiNotar, and the ensuing fake certificates for Google, among other noteworthy high-profile domains, has cast doubts on the reliability of a CA, and therefore on PKIs modelled as CAs too. In this paper, we propose a new approach to a healthcare PKI modelled on a blockchain, incorporating Elliptic Curve Cryptographic methods for secure key generations.

Summary In the present era, blockchain technology has an extensive variety of uses in the financial, marketing, and so forth. The performance and security of the blockchain system are directly affected by the consensus algorithm. Since there are 30 consensus techniques like proof of stake, delegated proof of stake, and proof of work, and so forth in the previous years, the operating efficiency, safety, and stability still lag behind the basic requirements. To this concern, this research manuscript introduces a novel consensus mechanism‐based game model using upgraded delegated proof of stake (UDPoS) and Nash equilibrium (NE) that is UDPoS‐NE. In a blockchain network powered by UDPoS, blockchain miners provide computing power to publish blocks. Due to a single miner's limited Computing Power (CP), miners frequently join mining pools and divide the pool's profits in accordance with their respective contributions. However, certain miners launch block‐withholding attacks that lead to loss the computer power and endanger the blockchain network's effectiveness. Therefore, NE is used to calculate cooperative game solutions and optimize policy decisions of the miners to frustrate the block withholding attack by the influence of stakes and computing power on producing blocks. Using this mechanism, efficiency, and stability in the consensus process is achieved through the combined influence of computing resources and stakes on block generation. Finally, the suggested model's applicability and validity are confirmed with a throughput (600 TPS), delay (3 s), and energy consumption (<100 KWh) for 10 nodes and processing time (0.9 s) for 200 nodes.

Multimodal biometric systems provide prospective advantages over traditional unimodal systems and are employed diversely for numerous applications. However, issues of data privacy and identity-theft emerges with the extensive use of these systems. To address these issues we propose a multimodal cancelable biometric system based on realtime Deep Feature Unification (DFU). For this, keys-based generic feature extraction is introduced to achieve revocability and dimensionality reduction. Non-invertibility is obtained through random projection of Key Deep features to Query Deep features. Proposed adaptive graph-based fusion process not only extracts complementary information across multiple modalities but also generates multimodal Unified template. The cross diffusion of normalized and optimal graphs ensure the unlinkability and robustness to dynamic environment. Proposed biometric system is assessed over benchmark datasets and shows promising performance against state-of-the-art methods. Average DI and EER achieved by proposed method are 10.35 and 0.12, respectively. Further, robustness against adversary attacks is demonstrated.

Abstract The concept of Proxy Re‐Encryption (PRE) was introduced by Blaze, Bleumer and Strauss at Eurocrypt in 1998. In this concept, a semi‐trusted proxy user acquires a re‐encryption key from the delegator. Then the proxy can easily convert the encrypted message under Alice's public key into an encrypted message under Bob's public key, without knowing the content of the message. For a unidirectional PRE, a master secret security (MSS) has been proposed as another security requirement by Ateniese et al. MSS provides security to the secret key of the delegator from computation by association with a malicious delegatee and dishonest proxy. In this study, first we have shown that Aono et al.'s scheme is not secure under the MSS model. Second, we have designed a unidirectional PRE scheme, based on Aono et al.'s study, and proved its security under the MSS model. In Table 2, we have shown that our scheme is more efficient in terms of computational and communication costs. Third, we have constructed a lattice‐based unidirectional PRE + scheme, similar to the scheme proposed by Wang et al. In this scheme the encryptor itself works as the delegator.

Maitra et al . (WCC‐2015) proposed the characterisation of valid states by reversing the one round of Salsa20. When revisited, a mistake was found in the one bit change of eighth and ninth word while reversing the one round result to a valid initial state. It was mentioned in WCC‐2015 that it would be an interesting combinatorial problem to characterise all such states. Thus, nine more values were characterised, leading to valid initial states. Aumasson et al . (FSE‐2008) attacked 128‐bit key Salsa20/7 with time and ChaCha6 with time. In this study, the attack was improved on 128‐bit key Salsa20/7 with time and ChaCha6 with time. Maitra (DAM‐2016) improved the attack on 256‐bit key Salsa20/8 and ChaCha7 by choosing the proper initialisation vectors. In congruence with this, 128‐bit key Salsa20/7 was attacked with time and ChaCha6 with time. Choudhuri and Maitra (FSE 2017) developed theoretical results on the differential‐linear cryptanalysis and thus improved the biases on Salsa/ChaCha. Theoretical work had been extended with triple bits from round to one bit m round of Salsa with the linear approximation holding the probability 1. In consideration of the linear approximation which holds the probability <1, linear approximation for three rounds from m to for Salsa and ChaCha was exhibited.