1. Surabaya, September 29-30, 2021
Analysis of Key Generation Which
Extracted from RSS for Handover
System in V2I Communication
Isna Yaumirrahma Saniyyah, Mike Yuliana, Amang Sudarsono
Department of Electrical Engineering
Politeknik Elektronika Negeri Surabaya (PENS)

2. Surabaya, September 29-30, 2021
Outline
• Introduction
• Proposed System
• Experiment
• System Testing
- Performance
- Encryption & Decryption
- Computation Time
• Conclusion and Future Works

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Introduction
• Vehicle-to-infrastructure (V2I) communication is
intended for vehicles making connections with
roadside units (RSUs) to exchange information
• Communication is based on received signal strength
measurements within a certain distance to generate a
secure key
• The information transmitted over a wireless network
requires security from attacks.
• A reliable security system is required for the security
and confidentiality of data protection on wireless
communication, and wireless key generation is
expected to be able to resolve these issues.

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Proposed System (1/2)
This system has four stages consisting of channel probing,
quantization, information reconciliation, and privacy
amplification. Single bit quantization purpose to convert signal
strength into bits, the results of the quantization process will
be checked and corrected for errors using BCH code, then
Universal Hash and the winner key is the key that has the
highest approximate entropy of NIST test. The secret key is
used to establish secure communications using symmetric
cryptography AES-128.

5. Surabaya, September 29-30, 2021
Proposed System (2/2)
In the communication scenario as shown
in Figure, vehicle is in a mobile state and
RSU as the access point of the V2I
network. When the V2I network is formed,
the RSS signal strength will be measured.
If vehicle is disconnected from the RSU,
vehicle will search for another RSU or a
handover process.

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Experiment (1/6)
Scenario Ping
Intervals
Traffic
conditions
Number
of
Packages
20S 20
KM/H
20ms Quiet 1000 data
20R 20ms Crowded
30S 30
KM/H
15ms Quiet
30R 15ms Crowded
40S 40
KM/H
10ms Quiet
40R 10ms Crowded
Measurement
Scenario
Measurements were carried out by obtain a signal strength of
1000 data with a different measuring scenario in quiet and
crowded condition. Measurements were made using two RSU
that were placed statically and one vehicle that moved. And
there is Eve positioned in the area around the RSU2 as shown
in figure.

7. Surabaya, September 29-30, 2021
Scenario
Before
Quantization
After
Quantization
Alfa
KDR
(%)
KGR
(bit/s)
20S V – RSU-1 1000 334 0.8 1.19 48.8
V – RSU-2 1000 216 0.9 0 48.2
20R V – RSU-1 1000 426 0.7 0.2 48.8
V – RSU-2 1000 472 0.5 36.6 48.5
30S V – RSU-1 1000 316 0.8 0.6 62.9
V – RSU-2 1000 205 0.8 18 62.7
30R V – RSU-1 1000 371 0.8 0.2 62.5
V – RSU-2 1000 298 0.9 8.3 62.4
40S V – RSU-1 1000 251 0.9 0 95
V – RSU-2 1000 214 0.8 4.2 92.6
40R V – RSU-1 1000 415 0.7 0.7 93.6
V – RSU-2 1000 205 0.8 20 94.9
Skenario Vehicle-
RSU1
Vehicle-
RSU2
20S 0.74 0.55
20R 0.85 0.21
30S 0.76 0.25
30R 0.81 0.47
40S 0.85 0.58
40R 0.85 0.20
Single Bit Quantization
Measurement
Correlation
Experiment (2/6)
The data before quantization is 1000 data and after
the quantization process, there is deletion of data. In
this section, analysis of KDR and KGR is carried out
to determine the performance of the system. In
measurement correlation orange color indicates high
correlation and blue color indicates low correlation, so
that the high correlation produces a small KDR value
and the low correlation produces a high KDR value

8. Surabaya, September 29-30, 2021
Error Correction BCH Code
Scenario Error Bit Remove
Block
Residual Bits KGR (bit/s)
20S V – RSU-1 10 1 324 45.1
V – RSU-2 0 0 216 46
20R V – RSU-1 6 1 420 47.2
V – RSU-2 196 32 276 27.8
30S V – RSU-1 16 2 300 57.5
V – RSU-2 49 8 156 45.9
30R V – RSU-1 11 1 360 58.9
V – RSU-2 28 4 270 54.1
40S V – RSU-1 5 0 246 86.7
V – RSU-2 22 3 192 77.5
40R V – RSU-1 19 3 396 84.7
V – RSU-2 49 8 156 69.5
Experiment (3/6)
BCH Code is needed to improve bit
match between users. The highest bit
error is at 20R which is 196 bits. The
high bit error is because of low
correlation measurement and also the
data pattern that does not match the
quantization method so that many bits
are different from one user to another.

9. Surabaya, September 29-30, 2021
Universal Hash 128 bit
Scenario Number of Initial
Bits
Number of
Keys
KGR
(bit/s)
20S V – RSU-1 324 2 32.4
V – RSU-2 216 1 25.3
20R V – RSU-1 420 3 39.4
V – RSU-2 276 2 24.1
30S V – RSU-1 300 2 43.9
V – RSU-2 156 1 34.1
30R V – RSU-1 360 2 37.8
V – RSU-2 270 2 45.4
40S V – RSU-1 246 1 40.3
V – RSU-2 192 1 45.5
40R V – RSU-1 396 3 68.8
V – RSU-2 156 1 49.5
Experiment (4/6)
Based on the table, it can be seen that
the number of incoming bits from the
BCH process affects the number of
keys that can be generate. One key has
a length of 128 bits.The maximum
number of keys that can be generated
is 3 keys. The higher the number of
keys, so the higher the KGR parameter
value.

10. Surabaya, September 29-30, 2021
NIST TEST
Approx. Entropy
Freq. Test
Block Freq.
Cumulative Sums
Run Test
Longest Run
Scenario of Measurement Number of Key Approx.
Entropy
20S V – RSU-1 2 0.791
V – RSU-2 1 0.973
20R V – RSU-1 3 0.668
V – RSU-2 2 0.520
30S V – RSU-1 2 0.949
V – RSU-2 1 0.109
30R V – RSU-1 2 0.183
V – RSU-2 2 0.372
40S V – RSU-1 1 0.564
V – RSU-2 1 0.354
40R V – RSU-1 3 0.762
V – RSU-2 1 0.251
Experiment (5/6)
Of several parameters for secret
key generation to be considered
is the Approximate Entropy value
must be above 0.01. Based on
the table, almost all the keys that
are the first priority have an
approximate entropy above 0.01.

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Secure Hash Algoritm -1
Scenario of Measurement Number of Key Remark (Match or
Not)
20S V – RSU-1 2 key 2 Match
V – RSU-2 1 key 1 Match
20R V – RSU-1 3 key 3 Match
V – RSU-2 2 key 2 Match
30S V – RSU-1 2 key 2 Match
V – RSU-2 1 key 1 Match
30R V – RSU-1 2 key 2 Match
V – RSU-2 2 key 2 Match
40S V – RSU-1 1 key 1 Match
V – RSU-2 1 key 1 Match
40R V – RSU-1 3 key 3 Match
V – RSU-2 1 key 1 Match
Experiment (6/6)
This is the result of SHA-1. As
shown on the table, all keys
generated match. So the hash
value are also matches. And only
1 key will be used as encryption
and decryption

12. Surabaya, September 29-30, 2021
System Testing (1/5)
Correlation
20KMH-S 20KMH-R 30KMH-S 30KMH-R 40KMH-S 40KMH-R
Vehicle-RSU1 0.74 0.85 0.76 0.81 0.85 0.85
Vehicle-RSU2 0.55 0.21 0.25 0.47 0.58 0.2
Vehicle-Eve 0.21 0.12 0.32 0.11 0.46 -0.02
RSU1-Eve 0.6 0.22 0.25 0.54 0.59 0.29
RSU2-Eve 0.86 0.88 0.88 0.91 0.76 0.88
-0.2
0
0.2
0.4
0.6
0.8
1
Measurement Correlation
Vehicle-RSU1 Vehicle-RSU2 Vehicle-Eve RSU1-Eve RSU2-Eve
The first test is correlation. On the
measurement, Eve is placed near
the RSU-2 so that the correlation
between the RSU2-Eve is very
high.

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KDR after Quantization
20S-1 20S-2 20R-1 20R-2 30S-1 30S-2 30R-1 30R-2 40S-1 40S-2 40R-1 40R-2
KDR (%) 1.19 0 0.2 36.6 0.6 18 0.2 8.3 0 4.2 0.7 20
0
5
10
15
20
25
30
35
40
KDR (%)
KDR (%)
System Testing (2/5)
The second test is KDR. KDR testing
after the quantization process in
order to find out the percentage
difference between the user. Based
on the slide the biggest KDR value
on 20R-2 scenario is 36.6%.

14. Surabaya, September 29-30, 2021
Key Generation Rate (KGR)
20S-1 20S-2 20R-1 20R-2 30S-1 30S-2 30R-1 30R-2 40S-1 40S-2 40R-1 40R-2
Quantization 48.8 48.2 48.8 48.5 62.9 62.7 62.5 62.4 95 92.6 93.6 94.9
BCH 45.1 46 47.2 27.8 57.5 45.9 58.9 54.1 86.7 77.5 84.7 69.5
UnivHash 32.4 25.3 39.4 24.1 43.9 34.1 37.8 45.4 40.3 45.5 68.8 49.5
0
10
20
30
40
50
60
70
80
90
100
KGR Comparison
Quantization BCH UnivHash
System Testing (3/5)
The third test is KGR. KGR testing
after the quantization process, BCH
Code, and Universal Hash. The
purpose of the Key Generation Rate
test is to determine the number of
bits generated in one second. The
higher the vehicle speed scenario,so
the higher the KGR value.

15. Surabaya, September 29-30, 2021
Encryption & Descryption AES-
128
20 KMH in Scheme Quiet
Key b'x8ax93xd2r:xdax16FS^px91%xdex07xfd'
Message Sent Ini adalah Pesan rahasia yang dikirim 20 sepi
Ciphertext b'x7fxb6xe1x88xa4xd6<xf0D]xecx06x00/xafxd9/xdb/^G
xfdxc0xbcW@xd9xb6xc9x99xddx84xf8xf3xc3xdcOxc6;xa
ax92xf1xadx07xb3'
Message
Received
Ini adalah Pesan rahasia yang dikirim 20 sepi
System Testing (4/5)
The next test is result of Encryption
and descryption. Based on this table, it
can be observed that the entire
encryption-decryption process can run
well, so the messages sent and
messages received are the same.

16. Surabaya, September 29-30, 2021
System computation time
Quantiz
ation
BCH
Univhas
h
NIST SHA-1
AES-
128
Total
Time
20KMH 0.194 0.179 0.841 1.006 0.148 0.215 2.65
30KMH 0.368 0.169 0.654 1.015 0.109 0.23 2.715
40KMH 0.279 0.242 0.908 1.013 0.148 0.209 2.888
0
0.5
1
1.5
2
2.5
3
3.5
Crowded Scenario
20KMH 30KMH 40KMH
Quanti
zation
BCH
Univha
sh
NIST SHA-1
AES-
128
Total
Waktu
20KMH 0.165 0.331 0.715 1.012 0.083 0.196 2.573
30KMH 0.28 0.19 0.615 1.014 0.12 0.219 2.559
40KMH 0.129 0.155 0.335 1.009 0.069 0.22 1.989
0
0.5
1
1.5
2
2.5
3
Quiet Scenario
20KMH 30KMH 40KMH
System Testing (5/5)

17. Surabaya, September 29-30, 2021
Conclusion
1. Single Bit Quantization process works well with the smallest KDR value
of 0% in the scenario of 20km/h and 40km/h in quiet conditions.
2. Error correction with BCH works well with the highest KGR of 86.7 bits/s.
3. The maximum number of keys generated by Universal Hash is 3 keys.
4. The average time it takes to generate a key in one scenario is about 2.5
seconds.
5. The NIST test has met the NIST requirements, namely the approximate
entropy value above 0.01 for all measurement scenarios.

18. Surabaya, September 29-30, 2021
Future Works
The future work is to make the key generation process with the shortest
computation time possible. Also, tunneling implementation using VPN to
improve system security.

19. Surabaya, September 29-30, 2021
References
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