Research shows that lightweight cryptography is essential for securing data in modern resource-constrained environments. While Simon, Speck, and ChaCha20 have been studied extensively on their own, there has been limited exploration of their combination in hybrid models. This project contributes to the field by demonstrating that hybrid algorithms not only provide better diffusion and security but are also efficient for securing various types of data in systems with limited computational resources.

To improve the security and efficiency of encryption, two hybrid cryptographic algorithms were designed: I. Simon-ChaCha20: combines the hardware efficiency of Simon with the high security and performance of ChaCha20.

II. Speck-ChaCha20: combines the simplicity and speed of Speck with the strong security of ChaCha20.

The hybrid algorithms were developed to take advantage of the strengths of their individual components while mitigating their weaknesses.

In this work, three prominent lightweight cryptographic algorithms—Simon, Speck, and ChaCha20—were selected for analysis and implementation. Simon and Speck, developed by the NSA, are block ciphers optimized for hardware and software efficiency, respectively. Simon is known for its simplicity and low resource consumption, making it a popular choice for constrained environments. Speck, on the other hand, is celebrated for its versatility and speed in software implementations. Meanwhile, ChaCha20, a stream cipher created by Daniel J. Bernstein, has gained widespread adoption due to its strong security guarantees, high performance, and adaptability across various platforms. Initially, these algorithms were implemented individually to evaluate their baseline performance and identify their strengths and limitations [2].

To further enhance the performance and security of these algorithms, hybrid cryptographic models were developed by combining the features of Simon, Speck, and ChaCha20. Two hybrid algorithms—Simon-ChaCha20 and Speck-ChaCha20—were created to leverage the complementary strengths of their respective components. The hybrid approaches were designed to enhance security, increase resistance to cryptographic attacks, and maintain efficient encryption and decryption times [9]. These hybrid models aimed to balance strong security with low computational overhead, addressing the specific needs of resource-constrained environments.

The performance of both individual and hybrid algorithms was evaluated using two primary metrics. The first was the avalanche effect, which measures the degree of change in output when a small change is made to the input. A higher avalanche score indicates better diffusion, a critical property for cryptographic robustness, as it ensures that even minor input variations result in significant changes in the output. This makes it difficult for attackers to identify patterns or predict outcomes. The second metric was encryption and decryption time, which evaluates the efficiency of the algorithms in processing different types of data. These include text files, audio files, video files, and Word documents. The encryption and decryption times were recorded to assess the practicality of the algorithms in real-world scenarios where speed and resource efficiency are crucial. Experimental results revealed that the hybrid algorithms outperformed their individual counterparts in terms of avalanche scores and diffusion properties. Both Simon-ChaCha20 and Speck-ChaCha20 demonstrated superior security, as evidenced by their high avalanche scores, indicating enhanced resistance to differential cryptanalysis and other potential attacks. In addition, the hybrid algorithms exhibited efficient encryption and decryption times across various data types, including text, audio, video, and Word files. This demonstrated their applicability in diverse use cases, such as secure communication, multimedia data protection, and document encryption, without compromising system performance.

In conclusion, this work successfully demonstrated the potential of lightweight cryptographic algorithms for secure and efficient data protection. By combining the strengths of Simon, Speck, and ChaCha20, the hybrid algorithms Simon-ChaCha20 and Speck-ChaCha20 provided enhanced security and efficiency, making them ideal for resource-constrained devices and environments. The findings of this work highlight the importance of hybrid cryptographic approaches in advancing lightweight encryption technologies, paving the way for more secure and efficient solutions in modern digital ecosystems. This work not only contributes to the field of lightweight cryptography but also addresses the pressing need for robust and resource-efficient data security mechanisms in today's interconnected world.

The results of the avalanche effect for the individual algorithms are as follows:

I. Simon: The Simon cipher exhibited a moderate avalanche effect, with about 48.5% of the output bits changing when a single input bit was flipped. While this demonstrates a reasonably balanced diffusion, it falls slightly short of achieving the ideal 50%, indicating a moderate sensitivity to input changes compared to other algorithms.

II. Speck: Speck displayed an avalanche effect of approximately 45%, slightly lower than that of Simon. Although this indicates a reasonable level of diffusion, it suggests that Speck may be marginally less effective in resisting cryptanalysis techniques that exploit input-output relationships.

III. ChaCha20: among the analyzed algorithms, ChaCha20 achieved the highest avalanche effect, with around 50.5% of the output bits changing due to a single input bit flip. This near-ideal diffusion highlights ChaCha20's robustness and is one of the key reasons it is regarded as a highly secure and reliable stream cipher.

The hybrid algorithms—Simon-ChaCha20 and Speck-ChaCha20 were evaluated to determine whether integrating a block cipher with a stream cipher could improve their diffusion properties, as measured by the avalanche effect. The findings revealed a noticeable enhancement in diffusion compared to the standalone algorithms:

I. Simon-ChaCha20: the hybrid Simon-ChaCha20 demonstrated a significant improvement, with approximately 51.3% of the output bits changing in response to a single bit alteration in the input. This increase highlights the effectiveness of combining Simon's block encryption capabilities with ChaCha20's strong stream cipher properties, resulting in a robust diffusion mechanism.

II. Speck-ChaCha20: similarly, the Speck-ChaCha20 hybrid achieved an avalanche effect of about 51.0%. This improvement underscores the advantage of integrating Speck's Feistel network structure with ChaCha20's high diffusion rate, leading to a more sensitive and secure encryption process compared to using Speck alone. The table below focuses on the Avalanche score of various algorithms as follows.

The execution time is a key metric for assessing the efficiency of a cryptographic algorithm. Lower execution time indicates better performance, especially in resource-constrained environments where processing power is limited. The following are the execution time results for the individual algorithms:

I. Simon exhibited a relatively fast execution time, averaging 0.15 milliseconds for encrypting a 64-bit block. Its efficient design, characterized by simple bitwise operations and a smaller number of rounds, makes it highly suitable for devices with constrained computational resources [9].

II. Speck also demonstrated strong performance, with an average execution time of 0.18 milliseconds for a 64- bit block. Its flexibility in block sizes and lightweight operations contributes to its efficiency, making it an excellent choice for low-resource environments [9].

III. ChaCha20, being a stream cipher, recorded a slightly longer execution time compared to the block ciphers, averaging 0.22 milliseconds for encryption. This difference can be attributed to its more intricate permutation rounds and larger key size.

IV. The Simon-ChaCha20 hybrid algorithm recorded an average execution time of 0.28 milliseconds for encrypting a 64-bit block. Although this represents a slight increase compared to Simon's standalone execution time, the hybrid remains efficient while providing enhanced security through improved diffusion properties, as demonstrated by its stronger avalanche effect.

V. The Speck-ChaCha20 hybrid showed an average execution time of 0.30 milliseconds for encrypting a 64-bit block. This modest increase in processing time is offset by the significant improvement in cryptographic strength achieved by combining the lightweight block cipher Speck with the robust diffusion capabilities of ChaCha20's stream cipher.

VI. The Simon-ChaCha20 and Speck-ChaCha20 hybrid algorithms required slightly more time for both encryption and decryption compared to their individual counterparts. This slight increase in processing time is typical when combining two algorithms with different structures and complexities.

Speck), 256 bits may use both 128 and stronger keys resist weaker keys are security with key (ChaCha20) 256 bits attacks better prone to brute-force length >128 bits attacks score data type (e.g., 0.7 score indicates better for Simon) diffusion of plaintext

Encryption X ms (Simon), Y Hybrid algorithms time ms (Speck), Z ms improve time over (ChaCha20) individual ones Decryption M ms (Simon), N Hybrid algorithms time ms (Speck), O ms may slightly reduce (ChaCha20) decryption time

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for protecting sensitive data.

Impact (with Impact (without Improvement (%) Algorithm) Algorithm) Better resistance to Weaker resistance to 5–15% improvement cryptanalysis; attacks; easier for in time vs. security increases attackers to exploit balance with hybrid computational complexity Higher diffusion; Poor diffusion; 10–30% minor changes in plaintext patterns improvement in plaintext produce may reflect in the avalanche score with major ciphertext ciphertext hybrid algorithms changes Balanced Potentially slower or 5–15% faster encryption time less efficient encryption with with optimized encryption times hybrid algorithms performance Faster decryption Slower access to 5–15% faster due to efficient decrypted data may decryption with hybrid affect usability hybrid algorithms configurations

Despite the increase in time, the hybrid algorithms still showed relatively efficient performance. The additional processing time was generally low and did not substantially affect the overall performance, especially for text-

For larger data types such as audio and video, the encryption and decryption times for the hybrid algorithms were a bit higher. This was expected, as encrypting larger and more complex data requires more computational resources. However, the difference in performance between the hybrid algorithms and individual algorithms was not significant enough to cause any major concerns, especially in cases where security is prioritized over

Text files are generally smaller and simpler to encrypt. The hybrid algorithms (Simon-ChaCha20 and Speck-ChaCha20) took a little longer to process compared to the individual algorithms, but the performance difference was not large. Moreover, the higher avalanche scores for the hybrid algorithms suggested they offered better security for text-based data. As the size and complexity of the data increased, particularly with audio and video files, the encryption and decryption times for all algorithms naturally increased. The hybrid algorithms showed a slight increase in encryption time compared to their individual counterparts, but the added security benefits from the hybridization outweighed the minor performance trade-off. Word documents showed similar results to text files, where the hybrid algorithms demonstrated a slight increase in processing time but offered higher security as indicated by the avalanche effect.

Based on the results from our experiments, the hybrid algorithms, particularly Simon-ChaCha20 and Speck-ChaCha20, provided stronger cryptographic security compared to the individual algorithms. The higher avalanche scores in the hybrid combinations suggest that these algorithms are more resistant to attacks that rely on input-output relationships, such as differential or linear cryptanalysis. This makes them more secure

While there was a minor increase in encryption and decryption times for the hybrid algorithms, this performance penalty was minimal. The speed of encryption and decryption remained within acceptable limits, especially for text-based data, where speed is often less of a concern. For larger data types like audio and video, the increase in time was more noticeable but still manageable, making the hybrid algorithms suitable for use in systems where security is paramount, such as secure communication networks, IoT devices, or encrypted storage systems. The Fig. 3, as mentioned below, is a combination of the Simon ChaCha20 algorithm, which gives us an encryption and decryption time for various data files.

Similarly, Fig. 4, as mentioned below, is a combination of the Speck ChaCha20 algorithm, which gives us an encryption and decryption time for various data files.

In summary, the combination of Simon and ChaCha20 or Speck and ChaCha20 offers a promising solution for lightweight cryptography, particularly in environments where security cannot be compromised. These hybrid algorithms balance encryption strength and computational efficiency well, making them ideal for use in both resource-constrained devices and high-security applications. Future work could focus on further optimizing the hybrid algorithms to reduce encryption and decryption times without compromising their cryptographic strength, as well as exploring their performance in more practical, real-world scenarios.