This paper applies Explainable Artificial Intelligence (XAI) to improve the interpretability of neural differential cryptanalysis on the SPECK cipher. We use Local Interpretable Model-agnostic Explanations (LIME) to analyse and visualise feature importance in neural distinguishers, giving signed contributions and absolute rankings. Signed contributions show whether, and how strongly, specific bit positions influence the model's decision, while absolute rankings reflect their importance regardless of sign. To study interactions beyond single bits, we introduce a Systematic Masking Approach to reveal relations among bits by testing if chosen combinations of masked bits alter classification accuracy. On Gohr's 8-round SPECK32/64 distinguisher, masking up to four-bit combinations shows that decisions involve multi-bit interactions rather than isolated single-bit effects. Although LIME highlights strong single-bit signals, masking reveals interaction patterns consistent with differential cryptanalysis. These findings clarify model behaviour in neural cryptanalysis and show XAI's value for exposing and visualising interaction structure in ciphertext features and decisions.

The immutability of blockchain, while essential for ensuring data integrity and traceability, presents challenges in scenarios requiring data modification, such as regulatory compliance with the General Data Protection Regulation (GDPR) and correction of erroneous transactions. To address this, we propose TAR−PCH, a novel chameleon hash scheme that enables fine-grained, policy-controlled rewriting of blockchain data under cloud-assisted environments. Our construction extends the Policy-Based Chameleon Hash (PCH) framework by incorporating partial policy hiding, user-level and attribute-level revocation, and traceability of malicious users. Leveraging efficient attribute-based encryption and white-box tracing, TAR−PCH enforces strong access control and accountability while outsourcing costly operations to the cloud. We formalize its security via indistinguishability and collision-resistance models, and our implementation demonstrates practical performance and scalability compared to existing schemes.

Policy-based chameleon hash (PCH) is one of the techniques used for rewriting transaction-level data stored in blockchains. This technique integrates the access policy of the attribute-based encryption (ABE) in the transactions and only allows users with attributes set satisfying the access policy to modify the transactions. However, some operations in the PCH-based rewritable blockchain solution require high computational cost which may impact the performance of user systems, especially on resource-constrained devices. To solve this problem, we propose an online/offline rewritable blockchain with auditable outsourced computation (OO-RB-AOC) scheme. We utilize the ring signature to ensure the credibility of multiple attribute authorities, and adopt the online/offline technique for generating the hash of the rewritable transaction. In addition, expensive computations (e.g., pairings) required for rewriting the transactions can be outsourced to the clouds. The users can rest assured that the computations from the clouds are correct with the audit mechanism of the proposed scheme. On the other hand, the proposed scheme offers a desirable feature for commercial application where the clouds can limit the number of outsourced requests according to the subscription of the users. We also prove the security of the proposed OO-RB-AOC scheme. Finally, we present a theoretical comparison and experimental analysis of the proposed scheme.

One of the solutions for rewriting blockchain data is to replace the standard hash function with a chameleon hash function. This enables users with the trapdoor to generate hash collision for rewriting operation. However, such rewritable blockchain solution may allow users to have unlimited rewriting permissions. This is undesirable as rewritable blockchains should still maintain a certain degree of immutability. In this paper, we propose a fine-grained one-time rewritable blockchain scheme that supports traitor tracing and bilateral access control. The proposed solution is the first that combines one-time chameleon hash function and traceable attribute-based encryption to realize one-time rewriting blockchain at the same time tracking for malicious users who leak the private key. Furthermore, our solution offers bilateral access control by integrating with fog computing. We also verify the performance of the proposed scheme with experimental analysis.

ABSTRACT On these days, users tend to access to online content via mobile devices, for example, e‐mails. Because these devices have constrained resources, users may wish to instruct e‐mail gateways to search through new e‐mails and only download those corresponding to particular keywords, such as “urgent.” Yet, this searching should not compromise the user's privacy. A public key encryption with keyword search (PEKS) scheme achieves both these requirements. Most PEKS schemes are constructed on the basis of bilinear pairings. Recently, Khader proposed the first PEKS scheme that does not require bilinear pairings and is provably indistinguishable chosen‐keyword attack (IND‐CKA) secure in the standard model. Such a scheme is more efficient than pairing‐based ones. In this paper, we show a drawback of Khader's scheme in that it depends on an unnecessary security assumption: Its IND‐CKA security requires its underlying identity‐based encryption building block to be indistinguishable chosen‐ciphertext attack secure. We construct a more efficient PEKS scheme that achieves the same level of PEKS security as Khader's but that only requires the underlying identity‐based encryption to be indistinguishable chosen‐plaintext attack secure. We give a direct proof that the proposed scheme is IND‐CKA secure. Our scheme outperforms other recent PEKS schemes in literature. Copyright © 2012 John Wiley & Sons, Ltd.

Password-Authenticated Key Exchange (PAKE) protocols allow parties to share secret keys in an authentic manner based on an easily memorizable password. Recently, Nam et al. showed that a provably secure three-party password-based authenticated key exchange protocol using Weil pairing by Wen et al. is vulnerable to a man-in-the-middle attack. In doing so, Nam et al. showed the flaws in the proof of Wen et al. and described how to fix the problem so that their attack no longer works. In this paper, we show that both Wen et al. and Nam et al. variants fall to key compromise impersonation by any adversary. Our results underline the fact that although the provable security approach is necessary to designing PAKEs, gaps still exist between what can be proven and what are really secure in practice.