A system for finding the secret key of the classical substitution cryptosystem using the Rotwild algorithm

Abstract

A system for identifying the secret key of a classical substitution cryptosystem using the Rotwild algorithm, comprising: an input module configured to receive ciphertext encrypted using a classical substitution cipher; a key generation module configured to generate initial key populations based on the principles of the red deer algorithm, with the key populations divided into stag and hind groups for exploration and exploitation of the key space; a suitability assessment module configured to evaluate the suitability of each generated key by decrypting the encrypted text and comparing the resulting plaintext with predefined language patterns and frequency distributions; a selection and crossing module configured to select the most suitable keys based on their suitability values ​​and to apply crossing techniques to generate a new generation of keys. a mutation module configured to introduce random mutations into the new key generation to maintain population diversity and prevent premature convergence; a convergence module configured to monitor fitness improvements across successive generations and determine the optimal key when the convergence criteria are met; an output module configured to output the detected secret key and the corresponding decrypted plaintext.

Description

[0001] The present invention relates to the field of cryptanalysis, in particular to the detection of secret keys used in classical substitution cryptosystems. Specifically, it relates to a system that uses the red deer algorithm (RDA) for the efficient detection of the secret key used in a classical substitution cryptosystem.

[0002] Classical substitution ciphers such as the Caesar cipher, the Atbash cipher, and monoalphabetic ciphers have been used for centuries to protect sensitive information by replacing each letter of the plaintext with another letter according to a fixed system or key. While these ciphers were effective in their time, the simplicity of their encryption methods makes them vulnerable to various forms of cryptanalysis, especially with the advent of modern computing power.

[0003] In a classic substitution cipher, the encryption key is a permutation of the alphabet. The security of the encrypted text depends entirely on keeping this key secret. However, due to the limited number of possible keys (26 factorial for monoalphabetic ciphers), attackers can use various cryptanalysis techniques to determine the key and decrypt the message. The most common attacks include frequency analysis, brute-force attacks, and pattern recognition.

[0004] One of the biggest drawbacks of classical substitution ciphers is their vulnerability to frequency analysis. Because certain letters and letter combinations (e.g., "th", "he", "in") occur more frequently in a particular language, attackers can analyze the frequency of characters in the ciphertext and map them to the most frequent letters in the target language. This method is particularly effective with long ciphertexts and can often reveal the key without having to test all possibilities.

[0005] Another conventional method for breaking substitution ciphers is the brute-force method, which tests all possible keys until the correct one is found. While this approach guarantees that the key will eventually be found, it is extremely inefficient, especially as the key's length and complexity increase. For monoalphabetic ciphers, the brute-force method is impractical due to the large number of possible keys (26!), resulting in excessive computation time and resource consumption.

[0006] Traditional cryptanalysis methods such as frequency analysis and brute-force methods are rigid and often do not adapt to different ciphertext lengths, different languages, or noise in the ciphertext (e.g., deliberate spelling mistakes or added random characters). This lack of adaptability reduces the effectiveness of these methods for more complex or obfuscated substitution ciphers.

[0007] Traditional approaches to cryptanalysis can be computationally intensive, especially when dealing with large ciphertexts or complex ciphers. Methods like brute-force attacks require significant computing power, which may not be feasible for fast or real-time decryption tasks. Classical cryptanalysis methods struggle with variations of substitution ciphers, such as polyalphabetic ciphers, where the key changes at different points in the ciphertext. These methods are designed to handle only a single substitution pattern and are ineffective against more complex encryption schemes. Many traditional cryptanalysis methods require considerable human expertise and intuition to recognize patterns, select the most likely key candidates, and interpret the results.This dependence on expert knowledge makes the process time-consuming and inaccessible to people without specialized training.

[0008] In the field of finding the secret keys of classical substitution cryptosystems, many modern optimization methods have been invented (e.g., hill climbing, simulated annealing, particle swarm optimization, genetic algorithms, ant colony optimization, cuckoo search, etc.). Of these techniques, cuckoo search is a recently proposed method for finding the secret key of classical substitution cryptosystems. However, this technique is less effective, less efficient, and less accurate in determining the secret key.

[0009] To solve the above problem, the invention aims to provide a system for determining the secret key of the classical substitution cryptosystem using the Rotwild algorithm.

[0010] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm efficiently detects the secret key used in the classical substitution cipher and reduces the required time and computing resources compared to conventional methods such as brute force and frequency analysis.

[0011] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm increases the accuracy of cryptanalysis by utilizing the Rotwild algorithm's ability to effectively explore and exploit the key space, thus ensuring that the correct key is identified even in the presence of obfuscation, noise, or complex language patterns.

[0012] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm creates a system that is adaptable to various forms of classical substitution ciphers, including monoalphabetic and polyalphabetic ciphers, and can process ciphertexts of varying length and complexity without loss of efficiency.

[0013] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm minimizes the need for human expertise in cryptanalysis, automates the key detection process, and enables non-experts to effectively decrypt classical substitution ciphers.

[0014] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm provides a scalable and flexible cryptanalysis system that can be easily adapted for use with different languages, encryption schemes and application areas, thus ensuring broad applicability for various cryptographic challenges.

[0015] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm enables the decryption of classical substitution ciphers in real time or near real time, making the system suitable for applications where fast and accurate cryptanalysis is crucial.

[0016] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm, which can be easily integrated into existing cryptanalysis tools and frameworks, thereby improving the general capabilities of cryptographic security analysis systems.

[0017] The system for detecting the secret key of the classical substitution cryptosystem using the Rotwild algorithm, which can detect the secret key even in cases where the ciphertext contains intentional obfuscations or errors, or is a variant of the traditional substitution cipher, such as those with multiple encryption layers.

[0018] In one embodiment, a system for determining the secret key of the classical substitution cryptosystem using the Rotwild algorithm is provided. The system comprises a data preprocessing unit, a unit that initializes some key candidates as Rotwilds, a unit that implements various functions of the Rotwild algorithm, a unit that repairs the solution generated by the previous Rotwild algorithm unit, a key extraction unit, and a termination condition unit. For the development of the system, the existing Rotwild algorithm is adapted so that the proposed system can discover the secret key used in the classical substitution cryptosystem more effectively, efficiently, and accurately than the modern optimization technique recently employed for this purpose, namely the cuckoo search.

[0019] The system was developed to discover the secret key used in classical substitution cryptography by applying the Rotwild algorithm. Classical substitution ciphers, such as Caesar ciphers and monoalphabetic ciphers, are fundamental cryptographic techniques in which each letter in the plaintext is replaced by another letter in a fixed system. Although these ciphers are easy to implement, their predictable patterns and limited key space make them vulnerable to various forms of cryptanalysis, such as frequency analysis and brute-force attacks. Conventional methods for breaking these ciphers, while effective, have significant drawbacks, including high computational weakness, susceptibility to noise and obfuscation, and reliance on human intervention.

[0020] The invention is explained again below with reference to the figure. It shows: Fig. : a system for finding the secret key of the classical substitution cryptosystem using the Rotwild algorithm.

[0021] Fig.This paper describes a system for discovering the secret key of a classical substitution cryptosystem using the Rotwild algorithm. The system comprises an input module, a key generation module, a fitness evaluation module, a selection and crossover module, a mutation module, a convergence module, and an output module. The input module is configured to receive ciphertext encrypted with a classical substitution cipher. The key generation module is configured to generate initial key populations based on the principles of the Rotwild algorithm, dividing the key populations into stag and hind groups for exploring and utilizing the key space.The fitness assessment module is configured to evaluate the fitness of each generated key by decrypting the encrypted text and comparing the resulting plaintext to predefined language patterns and frequency distributions. The selection and crossover module is configured to select the fittest keys based on their fitness scores and apply crossover techniques to generate a new generation of keys. The mutation module is configured to introduce random mutations into the new key generation to maintain population diversity and prevent premature convergence. The convergence module is configured to monitor fitness improvements across successive generations and determine the optimal key when the convergence criteria are met.The output module is configured to output the detected secret key and the corresponding decrypted plaintext. The suitability assessment module is configured to analyze language patterns, including common word structures, grammar, and syntax, to improve the accuracy of the suitability assessment. The suitability assessment module is configured to perform a frequency analysis by comparing the frequency of characters in the decrypted text to a reference frequency distribution specific to the target language. The selection and crossover module is configured to simulate the mating behavior of red deer, where dominant stags are more likely to pass on their traits to the next generation, thus refining the key population toward the optimal solution.The mutation module introduces mutations by randomly altering portions of the key population to explore new areas of the key space and avoid local optima.

[0022] The convergence module is configured to terminate the algorithm when the fitness of successive generations shows a minimal improvement, indicating that the optimal key has been identified. The key generation module is further configured to dynamically adjust the balance between exploration and exploitation based on the progress of the fitness scores to optimize the search process. The system was designed to determine the secret key of a classical substitution cipher using the Rotwild algorithm (RDA). Classical substitution ciphers, such as Caesar ciphers and monoalphabetic ciphers, are fundamental cryptographic techniques in which each letter in the plaintext is replaced by another letter in a fixed system.Although these ciphers are easy to implement, their predictable patterns and limited key space make them vulnerable to various forms of cryptanalysis, such as frequency analysis and brute-force attacks. Conventional methods for breaking these ciphers, while effective, have significant drawbacks, including high computational weakness, susceptibility to noise and obfuscation, and reliance on human intervention.

[0023] A metaheuristic optimization algorithm, inspired by the mating behavior of red deer, efficiently and accurately determines the secret key of classical substitution ciphers. The system consists of several modules, each performing specific tasks in the cryptanalysis process. The input module receives the ciphertext encrypted with a classical substitution cipher. The key generation module uses RDA to create initial key populations by simulating the division of red deer into stag and hind populations to explore different potential solutions. The fitness evaluation module assesses the viability of each key by decrypting the ciphertext and comparing the resulting plaintext to known language patterns and frequency distributions.The selection and crossing module then chooses the most promising keys and simulates the pairing process to generate new key candidates, while the mutation module introduces random changes to maintain diversity and prevent premature convergence to suboptimal solutions. The convergence module monitors the improvement of fitness scores across generations and determines when the optimal key has been found. Finally, the output module presents the found key along with the decrypted plaintext. The system's most significant innovation lies in its use of RDA, which strikes an effective balance between exploration (searching for new areas of key space) and exploitation (refining promising keys).

[0024] This approach significantly reduces the computational effort and time required to break a substitution cipher compared to traditional methods like brute-force attacks, which exhaustively test all possible keys. Furthermore, the system is robust against noise and can handle obfuscated or complex ciphertexts that would typically thwart conventional cryptanalysis techniques. The system is adaptable to various cipher types, including both monoalphabetic and polyalphabetic ciphers, and can be applied to ciphertexts of varying lengths and complexity. This flexibility makes it suitable for a wide range of cryptographic challenges. Moreover, the automation of this system minimizes the need for expert human intervention, making it accessible to non-experts while maintaining high accuracy.

[0025] The system for determining the secret key of the classical substitution cryptosystem using the Rotwild algorithm. The system comprises a data preprocessing unit, a unit that initializes several key candidates as Rotwilds, a unit that implements various functions of the Rotwild algorithm, a unit that repairs the solution generated by the previous Rotwild algorithm unit, a key extraction unit, and a termination condition unit. For the development of the system, the existing Rotwild algorithm is adapted so that the proposed system can determine the secret key used in the classical substitution cryptosystem more effectively, efficiently, and accurately than the modern optimization technique recently used for this purpose, namely the cuckoo search.

[0026] The secret key is involved in converting an original text (i.e., plaintext) into an unreadable text (i.e., ciphertext). In cryptography, this conversion process is called encryption, and the reverse conversion process is called decryption. The classical substitution cryptosystem under consideration here is a prominent example of classical cryptosystems, and modern optimization techniques have proven effective in successfully discovering its secret keys. In this work, we present a novel optimization method based on the Rotwild algorithm for finding the secret key of the classical substitution cryptosystem. The existing Rotwild algorithm has been adapted for this purpose. We compare the performance of the newly developed Rotwild algorithm with the established cuckoo search, using three metrics: effectiveness, efficiency, and accuracy.The results show that the proposed red deer algorithm is competitive with the cuckoo search in all areas.

[0027] The system is configured to improve three key measures regarding the detection of the secret key in the classical substitution cryptosystem, which are as follows: Effectiveness means that the secret key is found with fewer ciphertexts and a smaller part of the key space is examined.

[0028] Efficiency refers to the time costs associated with finding the secret key.

[0029] Accuracy refers to the proportion of key elements that were correctly identified in all passes.

[0030] The system uses two algorithms developed to successfully determine the secret key of a classical substitution cryptosystem. Both algorithms are self-explanatory. The novel secret key discovery system is proposed based on the Rotwild algorithm, which is used to discover the secret key of a classical substitution cryptosystem. The proposed system is capable of discovering the secret key more effectively, efficiently, and with greater accuracy than the recently developed optimization technique for this purpose, namely the cuckoo search.

[0031] The system can be used to determine the secret key of similar classical cryptosystems. This means the security industry can adapt the developed Rotwild algorithm for the automated cryptanalysis of similar cryptosystems. Reference symbol list 100 systems QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] Hill climbing, simulated annealing, particle swarm optimization, genetic algorithm, ant colony optimization, cuckoo search, etc.

[0008]

Claims

[1] A system for detecting the secret key of a classical substitution cryptosystem using the Rotwild algorithm, comprising: an input module configured to receive ciphertext encrypted using a classical substitution cipher; a key generation module configured to generate initial key populations based on the principles of the Red Deer algorithm, the key populations being divided into deer and hind groups for exploring and exploiting the key space; a suitability evaluation module configured to evaluate the suitability of each generated key by decrypting the ciphertext and comparing the resulting plaintext with predetermined language patterns and frequency distributions; a selection and crossing module configured to select the most suitable keys based on their suitability values ​​and apply crossing techniques to generate a new generation of keys a mutation module configured to introduce random mutations into the new key generation to maintain population diversity and prevent premature convergence; a convergence module configured to monitor fitness improvements over successive generations and determine the optimal key when the convergence criteria are met; an output module configured to output the recognized secret key and the corresponding decrypted plaintext. [2] The system of claim 1, wherein the suitability assessment module is further configured to analyze language patterns including common word structures, grammar, and syntax to improve the accuracy of the suitability assessment. [3] The system of claim 1, wherein the suitability evaluation module is configured to perform a frequency analysis by comparing the frequency of characters in the decoded text with a reference frequency distribution specific to the target language. [4] The system of claim 1, wherein the selection and crossover module is configured to simulate the mating behavior of red deer, with dominant deer being more likely to pass on their traits to the next generation, thereby refining the key population toward the optimal solution. [5] The system of claim 1, wherein the mutation module introduces mutations by randomly changing portions of the key population to explore new regions of the key space and avoid local optima. [6] The system of claim 1, wherein the convergence module is configured to terminate the algorithm when the fitness of successive generations shows a minimal improvement, indicating that the optimal key has been identified. [7] The system of claim 1, wherein the key generation module is further configured to dynamically adjust the balance between exploration and exploitation based on the progress of the fitness scores to optimize the search process.

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