Satellite Navigation Signal Authentication in GNSS: A Survey on Technology Evolution, Status, and Perspective for BDS
Round 1
Reviewer 1 Report
The article mainly introduces the principles, technology, development and challenges of satellite navigation signal authentication, which is detailed and rich in content. There are several questions:
1, P3-117: “and different authentication codes (fast channel and slow channel) are divided for each segment, channel ”: does the content in brackets indicate that different authentication codes are divided by fast or slow channels? But “ each segment, channel”: whether means that the channel and segment are in a coordinate relationship, please check whether this sentence is ambiguous.
2. The titles of 2.1.1 and 2.1.2 are the same,it may be better to distinguish them.
3, P5-153: “generates the symmetric key Keyi”: How to generate the Keyi on the user side? Should it be received at the next moment? Is it ambiguous to use “generate” here?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The key contributions as mentioned by the authors are
"This paper first expounds on the principles and technical architecture of satellite navigation signal authentication, then clarifies the development history of satellite navigation signal authentication, and finally proposes the BDS authentication service system architecture. It will provide technical support for the construction and development of the follow-up Beidou authentication service."
Overall, the English writing, contents organization and presentation quality is fine. I have few minor suggestions:
1: The Abstract is well-written. The readers can easily understand your contributions.
2: Might be you can add one more Keyword?
3: The organization of this study is missing.
4: I suggest a short and more clear summary should be added in start of each section to highlight main contents.
5: Line 9: What is GNSS? Define each abbreviation at the first place for better readability.
6: Can you find some relevant surveys or reviews and make a comparison of your contributions with existing works? Might be you can add in the end of Introduction?
7: Figures are nicely drawn and completely labelled.
8: Tables are nicely organized as well.
9: Some subsections in Section 2 require more references.
10: Section 3 and 4 are well supported with proper reference literature.
11: Please carefully check again if description of each figure is provided in the main text. Also consider it for each Tables.
12: Multiple references refer to URLs. Provided without access dates.
13: I suggest to revise Conclusion and make it more concise.
14: It will be better to add more references from 2021-2022.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
My comments for Authors:
1. abstract, all acronyms must be explained, e.g. GNSS
2. all figures in text, please add source of these figures
3. all tables in text, please add source of these tables
4. please check English translation of paper
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
General
This paper summarizes the existing GNSS authentication technology, designs a service architecture for next-generation BDS authentication, and clarifies the corresponding technical challenges.
I have read the paper in detail, and I think some modifications are needed. However, if this paper reflects some revisions, it seems sufficient to use them as basic data for developing and implementing next-generation BDS.
B. Comments
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(1) |
Some tables and figures are not mentioned in the body. Mention each of them in the appropriate position. For example, - Figure 1 - Table 1 - And so on.
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(2) |
It seems reasonable to write down the contents of the text explaining Figure 3 in more detail. For example, - In line 115, since the CHIMERA architecture utilizes TMBOC, that time-multiplexed version of BOC(1, 1) and BOC(6, 1), structure rather than the typical BOC type, it would be better to use an exact expression (such as TMBOC) to avoid the possible misunderstandings such as it can look like all types of BOC signal can utilize CHIMERA. - To add the contents of 'the four BOC(6,1) chips are never modified.' is needed. - In line 116, it seems reasonable that ‘1 ms chip’ is modified to ‘1 ms sector’. - In Figure 3, it seems reasonable that ‘1023 code’ and ’33 code’ are replaced to ‘1023 chips’ and ’33 chips’. - And so on.
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(3) |
2.1.1 and 2.1.2 have the same title. Confirmation is required.
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(4) |
In Table 3, ‘the spoofing jammer’ is wrong expression. The jammer should be differentiated from the spoofer because the purpose of the jamming and the spoofing are different and the resulting impact on the receiver is also different.
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(5) |
There is English problem in line 220.
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(6) |
The contents of Table 5 need to be modified. For example, - Shouldn’t ECDSA be added to the “Authentication Protocol” of the Galileo OS signal? Confirmation is required. - Reference is required regarding the introduction of NMA technology for Galileo PPP-RTK service signals. - GPS OS signal name modification is required. - And so on.
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(7) |
The contents of Table 7 need to be modified. For example, - I wonder how 40 bits were assigned to the MAC. Figure 2 shows that ‘MAC + Key’ is assigned 32 bits per page. - Doesn’t Galileo’s key length change depend on the setting? Please check. - And so on.
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(8) |
The title of 4.3 is limited to SBAS. Since this paper aims to design the next-generation BDS authentication architecture, it makes sense to modify the SBAS in the title to BDS.
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(9) |
Some references to the figures and tables need to be included. For example, - Figure 13 - References to authentication performance indicators are needed. - And so on. |
Author Response
Please see the attachment.
Author Response File: Author Response.docx
