=Paper=
{{Paper
|id=Vol-3896/paper22
|storemode=property
|title=Advanced data encryption method based on the monochrome pixel alphabet
|pdfUrl=https://ceur-ws.org/Vol-3896/paper22.pdf
|volume=Vol-3896
|authors=Vasyl Trysnyuk,Kyrylo Smetanin,Ihor Humeniuk,Oleksandr Lahodnyi,Volodymyr Okhrimchuk
|dblpUrl=https://dblp.org/rec/conf/ittap/TrysnyukSHLO24
}}
==Advanced data encryption method based on the monochrome pixel alphabet==
https://ceur-ws.org/Vol-3896/paper22.pdf
Advanced data encryption method based on
the monochrome pixel alphabet
Vasyl Trysnyuk1,†, Kyrylo Smetanin2,∗,†, Ihor Humeniuk2,†, Oleksandr Lahodnyi2,† and
Volodymyr Okhrimchuk2,†
1
Institute of Telecommunications and Global Information Space of the National Academy of Sciences of Ukraine, 13
Chokolivsky Blvd., Kyiv, 02000, Ukraine
2
Korolov Zhytomyr Military Institute, 22 Miru Ave., Zhytomyr, 10004, Ukraine
Abstract
Results of the encryption methods analysis showed, that modern approaches only consider the
cryptographic and steganographic properties of data protection algorithms and do not provide the
proper level of information confidentiality. An advanced data encryption method based on a
monochrome image alphabet, which takes into account cryptographic and steganographic properties
of information security, has been proposed in the article. The method utilizes mathematical
techniques to conceal the content of the original message, specifically by transforming its characters
into an alphabet-like form and applying mathematical operations to convert the result into ciphertext.
In combination with steganographic techniques, a monochrome image serves as the container,
forming the basis for constructing a pixel matrix. It is shown that the cryptographic resilience of the
method and information confidence exhibit functional dependency on the number of blocks into
which the original image is divided, as well as its key system and the dynamic nature of pixel alphabet
formation. The results of the experiment confirm that the method possesses the combination of
cryptographic and steganographic properties exhibits, high efficiency, and provides an adequate and
necessary level of information confidentiality. The conducted experiments have confirmed the
functionality and adequacy of the proposed data encryption method based on a monochrome image
alphabet. This allows us to recommend its practical use for information protection systems in
institutions and organizations.
Keywords
data encryption, monochrome pixel alphabet, steganographic and cryptographic properties,
cryptographic strength.1
1.Introduction and Literature Review
In the current stage of information technology development, the issue of safeguarding the
confidentiality of information resources is becoming increasingly relevant, timely, and
ITTAP’2024: 4th International Workshop on Information Technologies: Theoretical and Applied Problems, October 23-25,
2024, Ternopil, Ukraine, Opole, Poland ∗ Corresponding author.
†
These authors contributed equally. trysnyuk@ukr.net (V. Trysnyuk); kiry221982@gmail.com (K. Smetanin);
ig_gum@ukr.net (I. Humeniuk);
lov.82@ukr.net (O. Lahodnyi); okhrimchuk84@ukr.net (V. Okhrimchuk)
0000-0001-9920-4879 (V. Trysnyuk); 0000-0002-6062-550X (K. Smetanin); 0000-0001-5853-3238
(I. Humeniuk); 0000-0002-0812-939X (O. Lahodnyi); 0000-0001-7518-9993 (V. Okhrimchuk)
© 2024 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
CEUR
ceur-ws.org
Workshop ISSN 1613-0073
Proceedings
important. This is primarily due to the intensive scientific and technical progress in the field of
information security, information, and cybersecurity, and, as a result, the advancement of
hardware and software information technologies. These advancements pose a threat to
important information that is transmitted, processed, and stored by ICS. At the present time,
various cryptographic protection algorithms are employed to ensure an adequate level of
information and cybersecurity (achieving the fundamental properties of information). These
include encryption for confidentiality, hashing for integrity control, and electronic digital
signatures for availability (authentication) [1].
However, statistical data from global government response teams to cyber incidents indicate
an increase in the number of attacks in the global and national cyberspace. This includes
cyberattacks of the access type, whose purpose is to gain unauthorized access to important
confidential and/or personal information of citizens and government officials of Ukraine, among
others. The development of highly effective methods for cryptographic data protection is an
important component in addressing information and cybersecurity concerns. The primary goal
is to ensure a high level of cryptographic security in the developed encryption algorithms.
Cryptographic security in methods of cryptographic data protection refers to the property of
cryptographic algorithms and cryptographic protocols that characterizes their ability to resist
cryptographic analysis methods [2].
Therefore, despite the existence of a lot of the number of known encryption algorithms,
unauthorized access to information and access-based cyberattacks leading to data leaks and
violations of the fundamental properties of information, which regulated by information
security policies, are still prevalent [3]. Thus, there is a need for the development of a new
cryptographic method that combines the mathematical properties of steganographic and
cryptographic systems to provide robust information protection.
The known methods [4–7] only consider either the cryptographic or steganographic
properties of data protection algorithms and, therefore, are incapable of resisting cryptographic
attacks or attacks on the cipher. Let is analyse these methods. In scientific project [4] authors
have proposed the new technic of steganography, based on the use of LSB method, for raster
images of different colorful models for higher security and reliability level achievement.
The article [5] presents a method of data concealment in Portable Document Format (PDF)
files that utilizes dereferenced objects and secret splitting or combining algorithms. It has been
demonstrated that the hidden pages are not visible during regular use of the software. In [6], the
authors focus on the development of Public-Key Encryption with Keyword Search (PEKS) in
cloud technologies through comprehensive research. They also propose certain potential
applications for this method.
In the scientific project [7], a mechanism for one-to-one information exchange with
individual persons by concealing it from the rest of the group is developed. Given their
availability, digital images are the most suitable components for use as containers compared to
other objects available on the internet. The technique proposed encrypts the message within an
image. In the scientific project [8–12], the authors propose approaches to combining
cryptographic and steganographic properties for information protection. Their solutions are
based on methods such as LSB, DWT, and well-known symmetric and asymmetric
cryptographic data encryption algorithms. Therefore, in the scientific project [8], the authors
propose an advanced steganographic-cryptographic system that combines the features of
cryptography and steganography. In [9], various combinations of cryptographic and
steganographic methods are explored, highlighting that steganography based on DWT with
Advanced Encryption Standard (AES) provides a higher level of security while preserving image
quality. Additionally, a combination of the Data Encryption Standard (DES) cryptographic
algorithm and LSB steganography for ensuring information confidentiality is suggested in [10].
The authors [11] have implemented a combination of the encryption method Cipher Block
Chaining (CBC) and steganography method LSB-Sobel. This combination allows for achieving a
relatively high quality of stego-images by using the Sobel edge detection method. In the
scientific project [12] an increase in the level of information resistance of unauthorized access
(UAA) was implemented using cryptographic and steganographic algorithm of its protection
based on LSB-method, AES-algorithm and exchange opened keys protocol Diffie-Hellman. The
analysis of scientific achievements indicates a large number of possible promising and
implemented combinations of steganographic and cryptographic methods for information
security. However, all of them are based on the use of known and outdated algorithms, the study
of cryptographic stability of which indicates the imperfection of these cryptographic systems.
This is due to the possibility of successful implementation by the violator of the UAA and attacks
on the cipher. And it is carried out in order to violate the integrity and confidentiality of
information that circulates in information systems or systems such as “sender-recipient”.
To achieve goal it’s necessary to: form pixel alphabet 𝐵 = {𝐵1,𝐵2,𝐵3, 𝐵4} for Ukrainian and
English alphabet symbols, numbers and punctuation symbols; synthesize and detail method
stages, which takes into account cryptographic and steganographic algorithm properties of
information security. After that for outgoing message 𝑀𝑒𝑠 = {𝑀1,. . . , 𝑀𝑚} conduct verification of
suggested method; conduct research of studying the impact of the parameters of a graphical
container on the effectiveness of the proposed method.
2.Materials and methods
The proposed data encryption method, which combines the mathematical properties of
steganographic and cryptographic systems and is based on the use of a pixel alphabet of a
monochrome image, consists of five main stages: forming the pixel alphabet, creating the pixel
matrix, key pair generation, encryption (forming ciphertext), and decryption.
A detailed scheme of the functioning of the developed method is presented in Fig. 1.
Let's describe each of the method's stages in detail. In the first stage, a specific static range of
values [000;255] is assigned to every possible character of the output message that can be used in
the message. This range corresponds to the brightness range of pixels in a digital raster image:
𝐵 = {𝐵1,𝐵2, 𝐵3,𝐵4} ,
where 𝐵1 – for letters in Ukrainian alphabet,
𝐵2 – for letters in English alphabet,
𝐵3 – for numbers,
𝐵4 – for special symbols and punctuation.
Figure 1: Block diagram of the proposed method.
The possible variant of pixel alphabet can be presented as follows: for
letters in Ukrainian alphabet:
𝐵1 = {𝐵"а", 𝐵"б", . . . , 𝐵"я"} , (1)
where 𝐵1 ∈ [000; 095] and for example 𝐵"а" ∈ [000; 003]; for letters
in English alphabet:
𝐵2 = {𝐵"𝑎", 𝐵"𝑏", . . . , 𝐵"𝑧"} , (2)
where 𝐵2 ∈ [096;173] and for example 𝐵"𝑎" ∈ [096; 098]; for
numbers:
𝐵3 = {𝐵"0",𝐵"1", . . . , 𝐵"9"} , (3)
where 𝐵3 ∈ [174; 203] and for example 𝐵"0" ∈ [174;176]; for special
symbols and punctuation:
𝐵4 = {𝐵"?", 𝐵"!", . . . , 𝐵"_"} , (4)
where 𝐵4 ∈ [204; 255] and for example 𝐵"?" ∈ [204; 206].
The example for numbers of synthesized pixel alphabet is presented in Table 1.
Table 1
Pixel alphabet of numbers
Numbers Value of brightness Numbers Value of brightness
0 174–176 5 189–191
1 177–179 6 192–194
2 180–182 7 195–197
3 183–185 8 198–200
4 186–188 9 201–203
It is worth mentioning, that symbols for message, choose out of the static range, that
increases, which, in turn, increases the level of cryptographically resistant of such an algorithm.
The pixel alphabet is synthesized on one side of the information exchange and transmitted to the
other side through secure data transmission channels or is coordinated without any third party.
That is, the pixel alphabet is generated or agreed upon only between the recipient and sender.
Besides this, advisable to change the pixel alphabet periodically.
The next step is the formation of a pixel matrix. At this stage, an image with a consistent color
model (usually monochrome) is arbitrarily selected, and the number of blocks into which it will
be divided and numbered is determined. For each block, the average brightness
values of the pixels are calculated I [ N ], where [𝑁𝑖] – the block numbers, which are then recorded
i
or mapped into the pixel matrix.
Similarly, to the alphabet, it is advisable to periodically change either the image itself or the
number of blocks into which it is divided. It's worth noting that the choice of a raster image and
the number of blocks are coordinated by both sides of the exchange, and for algorithm usage,
only the pixel matrix is retained.
During the generation of a set of encryption keys, the sender arbitrarily selects block
numbers from the pixel matrix and their corresponding average brightness values, which
determine the encryption key.
The main step of the method is the process of encrypting information: each character in the
original message is replaced using the synthesized alphabet with a corresponding value from its
assigned range. Then, a set of sums is calculated between the transformed message into the pixel
alphabet and the corresponding values of the pixel matrix 𝐼𝑐𝑟[𝑖] using the encryption key set:
. (5)
Afterwards, the ciphertext is calculated as:
𝐶𝑜𝑑𝑒(16) = {𝐶𝑟(16) ⊕ 𝑁(16)}. (6)
It's worth mentioning that to obtain the ciphertext, the corresponding values are used in the
hexadecimal system. This rule also applies to transmitting the ciphertext. As a result, the
ciphertext appears as a sequence of pairs of ciphertext values 𝐶𝑜𝑑𝑒(16) and block numbers 𝑁(16)
each character of the message. A notable feature of the method is that multiple characters can be
assigned to the same block, which further enhances the algorithm’s cryptographic resistance.
On the recipient’s side, the reverse process of encryption, decryption, is performed. The
result of this stage is the retrieval of the original message.
3.Experiment, Results and Discussions
In order to confirm the functionality of the proposed enhanced data encryption method based on
the monochrome image alphabet, an experiment was conducted using the verification method
selected in reference [13].
To conduct the experiment in the Python programming language, the method proposed in
the article was implemented. During the experiment, encryption of the open-text message was
performed based on the developed method, followed by the transmission of the ciphertext over a
network, and then the decryption of the received ciphertext on another host. So, for conducting
the experiment, the following original message was chosen: Cybersecurity.
According to the first stage of the method, all characters of the input message were
transformed based on the proposed technique outlined in [14] Alphabet encryption of letters of
the English alphabet.
Table 2
Message transformation to pixel alphabet
Outgoing message symbol The transformation result
C 102
Y 169
B 100
E 108
R 147
S 150
E 109
C 104
U 156
R 147
I 120
T 153
Y 168
In this way, the input message takes the following form:
𝐼𝑐𝑟 = {102; 169; 100;108; 147; 150;109; 104; 156; 147;120; 153; 168}. (7)
In the next stage, a test image with dimensions of 264x192 pixels was selected and divided
into 25 blocks (5 by 5). Using the Python Imaging Library (PIL) library, the average brightness
values of the pixels in each block were calculated, and a pixel matrix was generated as follows in
Table 3.
Table 3
Formation of pixel matrix
Columns of matrix Rows of matrix
- 1 2 3 4 5
1 219 216 203 188 225
2 213 210 234 232 223
3 210 193 96 198 170
4 198 204 212 226 224
5 198 204 215 185 209
After the formation of the pixel matrix, the encryption process of the message takes place. To
encrypt the characters of the message, a set of keys was generated by randomly selecting block
numbers from the pixel matrix and their corresponding average brightness values using the
“random” module. The number of keys corresponds to the number of characters in the message
being encrypted. Therefore, during the experiment, a set of block numbers from the image was
formed (Table 4).
Table 4
The set of encryption keys
Block numbers Hexadecimal representation
12 0C
54 36
33 21
22 16
12 0C
25 19
12 0C
51 33
31 1F
51 33
52 34
35 23
53 35
Mathematically, the set of keys has the following form:
𝑁 = {12;54; 33; 22; 12; 25; 12; 51; 31; 51; 52; 35; 53}. (8)
In the next stage, the sum is calculated according to expression (5), transformed into the pixel
alphabet message (7), and the corresponding values of the pixel matrix (Table 3) are used with
the encryption key set (8). As a result, the following values are obtained:
𝐶𝑟 = {318; 354; 196;318; 363; 373; 325;302; 366; 345;324; 323; 383}. (9)
In the final stage, before sending the message to the recipient, it is transformed into
ciphertext according to expression (6). As a result of this transformation, obtained message has
the following form:
𝐶𝑜𝑑𝑒(16) = {132;154; 𝐸5; 128; 167; 16𝐶; 149; 11𝐷; 171; 16𝐴; 170;160; 14𝐴}. (10)
Therefore, by using the proposed method, the encrypted message (Table 5) is presented in the
hexadecimal numbering system.
Table 5
Components of ciphertext
Key Ciphertext
0C 132
36 154
21 0E5
16 128
0C 167
19 16C
0C 149
33 11D
1F 171
33 16A
34 170
23 160
35 14A
The recipient receives tuples of pairs consisting of ciphertext values (10) and block numbers
(8) for each character of the message:
{(132,0𝐶); (154,36); . . . ; (160,23);(14𝐴, 35)}. (11)
After receiving the encrypted message, the recipient performs decryption (the reverse
execution of the steps).
When analysing the effectiveness of the proposed method, we used incoming messages with
different numbers of characters are provided in Table 6.
Applying the mathematical apparatus proposed in this paper, we obtained results, the
analysis of which confirms the adequacy of the method of data encryption and decryption.
In addition to testing the functionality of the proposed data encryption method based on the
monochrome image alphabet, the experiment also investigated the influence of factors such as
image size, the number of blocks into which the image is divided, and/or the number of
characters in the encrypted message on the data encryption speed. As a result of the study, the
time indicators depending on the selected parameters (Table 6).
Table 6
Experimental results of research
Size of the Number Number of Time of
image in pixels of blocks symbols in the message encrypting, sec
13 0:00:00.025991
264x191
331 13 0:00:00.030206
5x5
331 0:00:00.384151
1200х675
0:00:00.389754
13 0:00:00.026113
264х191
331 13 0:00:00.030313
10x10
331 0:00:00.384858
1200х675
0:00:00.391086
As a result of the conducted experiment to assess the functionality and adequacy of the
proposed method, the following conclusions were made:
1. The method possesses cryptographic properties, utilizing mathematical techniques to
conceal the content of the original message (transforming its characters into an alphabetlike
format and performing a mathematical operation to convert the result into ciphertext). It also
combines steganographic properties, using a monochrome image as a container, which forms
the basis for constructing the pixel matrix.
The computational complexity of the mathematical apparatus in the proposed method is
relatively low, yet it demonstrates high efficiency and is capable of resisting cryptographic
analysis methods.
2. As a container for constructing the pixel matrix, it is indeed possible to use
monochromatic raster images with varying resolutions and different geometric dimensions.
This flexibility in choosing the container makes the method adaptable to various scenarios and
use cases.
If a color raster image is chosen as the container, the pixel alphabet range increases threefold
due to the use of all three color channels. (R, G and B). As a result, the number of possible
variations in synthesizing the alphabet increases. For example, values for English language
characters can be chosen from the [0; 255] range in the R channel, punctuation marks and special
characters from the G channel, and digits from the B channel, and so on. This expanded range of
possibilities in a color image allows for more diverse and robust encryption. The size of the
image has the most significant impact on the speed of the data encryption procedure,
particularly increasing the size of the image results in an increase in the duration of the
encryption process. However, the encryption time of the message is almost independent of the
number of blocks into which the image is divided and the number of characters in the message
itself. This suggests that the primary factor affecting encryption speed is the image size.
3. The number of blocks into which the original image (container) is divided and its color
system indeed have a direct impact on the set of possible variations in forming the ciphertext.
This, in turn, increases the level of cryptographic resistance of the method.
4. The set of variations in the pixel alphabet depends directly on the characters in the
original message (including the alphabet used, punctuation marks, digits, etc.) and the color
system of the raster image. The degree of periodicity in changing the pixel alphabet is directly
proportional to the level of confidentiality of the information that needs to be encrypted. In
essence, greater diversity and complexity in the formation of the pixel alphabet contribute to
higher information security.
The analysis of the results in Table 5 indicates that all encryption stages have been completed
for the initial values of the original message (Table 2), resulting in the corresponding ciphertext
(11). It is important to note that this is one of the possible variants of the encrypted message,
based on the specific choices of pixel alphabet range values for each individual character of the
original message. Furthermore, the set of possible ciphertexts also depends on the formation of
the pixel matrix, including the number of blocks into which the raster image is divided. This is
because the same block or different blocks can be used to select the encryption key for the
characters of the original message. Taking into account the image size and the number of blocks
(Table 6) into which it is divided allows for an evaluation of the set of possible ciphertexts as well
as the time required for the encryption procedure.
The data encryption method based on a monochrome image alphabet is suitable for secure
transmission of confidential or important information in conditions where there may be threats
like cyberattacks, UAA, or other fraudulent actions, , even when the data network is secured
using a cluster approach [15]. Consideration of encryption parameters (such as the periodicity of
pixel alphabet changes, increasing the number of blocks in the pixel matrix, and so on)
significantly enhances the cryptographic resilience of the proposed method. It also enhances the
level of information confidentiality protection and resistance against UAA.
4.Conclusions
The scientific novelty of obtained results involves improving the data encryption method based
on a pixel alphabet by changing the order and mathematical apparatus. The proposed method,
unlike known and existing ones, does not utilize the functionality of cryptographic and
steganographic encryption systems but rather their structural properties. It provides an
adequate level of information confidentiality and possesses a sufficient and necessary level of
cryptographic resilience. The mathematical apparatus of the data encryption method
implements the concealment of the message content, while the pixel matrix and its usage
represent the very existence of such a message. By using the blocks into which it is divided as
mathematical components of encryption, namely their average pixel brightness values obtained
at the stage of pixel matrix formation.
The practical orientation of the study lies in the ability to apply the proposed data encryption
method to ensure secure and confidential exchange of important information between
organizations and institutions.
Prospects for further research include improving the mathematical apparatus of the
encryption method, considering pseudorandomness and the dynamic formation of the pixel
alphabet, and utilizing various color systems for raster images.
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