Time-Modifiable Chameleon Hash for Building Redactable Blockchains

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper presents a time-modifiable chameleon hash (TMCH) construction aimed at enabling redactable blockchains with traceable and time-bounded updates. However, it has come to my attention that a closely related article, co-authored by one of the authors, was recently published in Electronics (Chen et al., 2025, "Building Traceable Redactable Blockchain with Time-Verifiable Chameleon Hash"). this previously published work introduces a time-verifiable policy-based chameleon hash (TPCH) and addresses similar objectives through the design of Hash, Adapt, and Update algorithms within a redactable blockchain system.

Upon review, I observed substantial conceptual, structural, and methodological similarities between the two papers particularly in the system model, security notions, core algorithms, and performance evaluation settings. Given these overlaps, it is not entirely clear whether the current manuscript is intended to be an extension, a generalization, or a re-framing of the earlier published work.

I strongly encourage the authors to explicitly clarify the relationship between this manuscript and the previous publication. In particular, it would be valuable to:

1. Clearly acknowledge the existence of the earlier work within the introduction or related work section.
2. Make clear what is new and original in the current manuscript that was not addressed in the prior work.
3. Justify why the proposed TMCH model constitutes a distinct and novel contribution whether theoretically, practically, or in terms of abstraction or scope.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This article has a very good feature in employing the fantastic Chameleon Hash method trying to improve the operations of blockchains. But the major weakness is that if the blockchain can be redacted, then it can also be tampered which is hard to believe at this moment. Suppose the TMCH is theoretical sound, how to make all changes to the whole blockchain as it should be decentralized elsewhere since this is one key advantage of using blockchain.

1) The abstract is very clear but too long to be the abstract. Should it be trimmed down or move some explanations to the Introduction section or insert into Contribution section?

2) The System Framework is over-simplified. It should contain the details to let the layman appreciate the fantastic design of the TMCH. However, the Building Blocks is too mathematical while losing the written textual explanations of the mechanism. The mathematical section is important as it lays the foundation of theoretical soundness but it takes major proportion of this article and thus losing focus.

3) The presentation is a big problem. Inside Performance Evaluation section, it is referring to Table 1, 2 and the several figures which are in section 4 and Conclusion section. In addition, the explanations or legends of the figures and tables are insufficient.

4) Last but not least, since security should be walking with both legs of theoretical and practical, this article is too theoretical but it is so interesting to have the figures inside Table 2, how come the figures? The proper way is to have a comprehensive testing of the TMCH and KXY using public datasets or own experiment.

Comments on the Quality of English Language

There are quite a number of obvious grammatical mistakes found. It must have English proof-read before publication.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper introduces a new chameleon hash construction called Time Modifiable Chameleon Hash (TMCH). It revisits chameleon hashes' underexplored “uniqueness” property and proposes leveraging its violation as a feature for time-sensitive applications, such as redactable blockchains. The paper provides one concrete TMCH constructions (based on BBS), and presents theoretical and experimental evaluations that demonstrate the effectiveness and practicality of the proposed schemes.

However, Please consider the following suggestions:

 

-Prior to exploring the security requirements in the first column of page 4, kindly clarify the objective of the update algorithm: what does it contribute to achieving? And why is it necessary to have such an algorithm?

 

-When referring to concepts like collision resistance and indistinguishability, please use the term "security properties" instead of "securities". The latter is non-standard and confusing.

 

-In Section 1.3, what is meant by a "dominant algorithm"? Does it refer to algorithms that are highly regarded or widely used in a certain application field? Please provide an explanation.

 

-The rationale behind TMCH is not clear. Specifically, the paper proposes incorporating the time taken for generating, verifying, and creating collisions in chameleon hash, but it fails to adequately justify the need for this.

 

-Although the perspective on uniqueness is novel, the underlying cryptographic tools (such as BBS) are standard, and the design choices are to some extent incremental.

 

-The core idea of introducing time verifiability by means of controlled violation of uniqueness is innovative and promising. However, the relationship between the uniqueness property and other security concepts (IND and CR) could be elaborated more thoroughly. While the paper asserts transferability, the logical and formal reasoning leading to this conclusion is dense and may not be easily understandable.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Please refer to the comments below for potential improvements:

- The abstract needs to be re-drafted to be self-contained, clearly showing the hypothesis, methodology, techniques and tools used, and the results obtained. There is no need to introduce the related work too much in the abstract.

- In Section 1 [Introduction], it is suggested to divide it into three subsections [Motivation], [Contribution], and [Structure], which respectively introduce the motivation, contribution, and structure of this study, and facilitate readers to quickly find the information they want.

- Please separate [related work] into a separate section and provide a detailed introduction to the advantages and disadvantages of existing related research. It is best to have a clear comparison in the form of a table.

- It is suggested to create a separate section with the content of [System Framework] and Sections 2, 3, and 4 to introduce the system design and related theories of this study.

- For the [Contributions] subsection, it is recommended to list it in the form of entries to facilitate readers in quickly identifying the main contributions of this article.

- It is recommended to introduce the meanings of some common and important parameter symbols in the formula of the article through a table.

- There are some places in the article, especially the lack of half brackets in the formulas, such as lines 228 and 252, equations 5 and 6. It is recommended to carefully check the entire article to avoid such problems.

- What are the meanings of several consecutive equal signs in a row of equations 4, 5, and 6? If it is the derivation process of the formula, can the result be directly given?

- Section 5 [Performance Evaluation] should be the focus of this article, and it is recommended to add some sub sections such as [Experimental Settings], [Running Costs], etc.

- Figures 2-5 are too small, it is recommended to adjust the image size.

- In section 6 [conclusion], it is suggested to introduce the application scenarios of the method proposed in this paper and to discuss possible future research directions.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

the authors have made substantial improvements to the manuscript, particularly in terms of transparency, comparative positioning, and formal clarity. However, a few minor but important revisions remain necessary:

1. in section 5.1, please specify the test environment used for performance benchmarking (e.g., CPU model, RAM, cryptographic library). Also, label the Y-axes in figures 2–5 with appropriate units (e.g., milliseconds)

2. in table 2, define or briefly explain terms like “KeySwitch” and “Adapt” for readers less familiar with internal notation

3. if possible, mention the practicality or implementation readiness of the TMCH scheme (e.g., whether a prototype exists or plans for deployment in permissioned chains)

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks for your numerous modifications that make this article more aligned with the requirements of an academic research. This article has been modified to enhance the practical aspect while retaining its powerful mathematical derivations and proofs. I am satisfied with the changes.

Comments on the Quality of English Language

May be due to the big change, it would be nice if the English structure of some inserted contents can be rewritten for smooth reading and coping with the previous sentences.

 

Author Response

Thank you sincerely for your positive feedback and recognition of our revisions. We greatly appreciate your guidance throughout the review process—your insights have been instrumental in enhancing the clarity, practical relevance, and academic rigor of our manuscript.

We are pleased to hear that the modifications (including strengthening the practical aspects while preserving mathematical rigor) meet your expectations. We have carefully incorporated all your suggestions to ensure the work aligns with academic standards, and we hope the revised version now presents a more balanced and impactful contribution.

Thank you again for your time and valuable input, which have significantly improved the quality of our paper.

Reviewer 4 Report

Comments and Suggestions for Authors

As the author has revised the manuscript according to my suggestions and rechecked all its contents, I suggest accepting the manuscript.

Author Response

Thank you so much for your thorough review and positive recommendation to accept our manuscript. We greatly appreciate your valuable suggestions throughout the review process—your insights have been crucial in refining the manuscript’s clarity, rigor, and overall quality.

We are delighted to hear that our revisions align with your expectations and that you recognize the improvements made. Your careful guidance has significantly strengthened the work, and we are grateful for the time and effort you have dedicated to evaluating our manuscript.

Thank you again for your support and encouragement. We will continue to uphold academic rigor in our future work.