Description:FIELD OF THE INVENTION

[0001] The present invention relates to a method for encrypting a digital audio file that is capable of protecting digital audio files from unauthorized access by applying encryption techniques in view of safeguarding user content against theft and misuse.

BACKGROUND OF THE INVENTION

[0002] In the digital age, audio files are among the most commonly shared and stored forms of multimedia content. As the volume of digital audio data increases, so does the need to protect this information from unauthorized access, tampering, and piracy. Ensuring the confidentiality and integrity of audio data is crucial for various applications, including personal communication, media distribution, and confidential recordings.

[0003] Traditionally, securing digital audio files has relied on standard encryption techniques, such as symmetric and asymmetric cryptography. These techniques often involve encrypting the entire file or specific segments using well-known protocols AES or RSA. While effective to some extent, these approaches primarily focus on data encryption without considering the unique characteristics of audio signals. Additionally, conventional encryption methods can be computationally intensive, leading to slower processing times, which is problematic when handling large audio files or real-time streaming. Moreover, traditional methods often do not incorporate advanced transformations tailored to audio data, leaving potential vulnerabilities that could be exploited through cryptanalysis or statistical analysis.

[0004] Another common approach involves converting audio files into compressed formats before encryption, but this can lead to loss of quality and may not adequately protect the content from sophisticated attacks. Furthermore, many existing techniques do not provide comprehensive analysis or validation tools to assess the strength of encryption, leaving users uncertain about the security level of their protected data.

[0005] DE102022004784A1 discloses a method for encrypting and decrypting a data stream with a random block size in a communication system. Such methods for encrypting and decrypting a data stream with a fixed block size are known, e.g. Advanced Encryption Standard (AES), Salsa20 and the closely related ChaCha (e.g.: https:/Ien.wikipedia.org/wiki/Salsa20). The aim of the invention is to provide a method that uses two different entropy sources, namely the uniform distribution of the cryptographic hash function used and a cryptographically secured pseudo-random number generator, in order to achieve probabilistic encryption and bring it as close to noise as possible. For this purpose, the invention proposes a method for encrypting and decrypting a data stream with a random block size in a communication system, which comprises the method steps of claims 1 and 2.

[0006] CN118200827A discloses a digital microphone with an audio encryption function, a main control chip, a method and a system, wherein an encryption module is arranged in the digital microphone so as to realize the mode of encrypting an audio stream in the digital microphone in real time and decrypting the audio stream in the main control chip of a user, the audio stream is encrypted in the digital microphone in real time, the problem that audio data transmission is easy to intercept and leak is solved, and the data security is improved. The ChaCha20 algorithm is adopted to realize efficient audio encryption, so that encryption strength and processing performance are ensured, and the method is suitable for resource-limited environments. The encryption efficiency is improved, the system resource occupation is reduced, and the method is applicable to various audio devices and systems. By means of end-to-end encryption, the safety of the communication environment is improved, and leakage of personal information and sensitive data is effectively prevented.

[0007] Conventionally, many digital audio encryption techniques have been proposed to secure multimedia data during transmission and storage. Nonetheless, these conventional methods often lack often exhibit vulnerabilities to cryptanalytic attacks and fail to maintain the structural fidelity of the original audio signal after decryption, thereby compromising playback quality. Additionally, many existing methods do not incorporate comprehensive security validation metrics, which limits their effectiveness against emerging threats.

[0008] In order to overcome the aforementioned drawbacks, there exists a need in the art to develop a method that requires to be capable of protecting digital audio files from unauthorized access by applying encryption techniques. In addition, the developed method need to be capable of facilitating fast and reliable encryption processes, allowing users to securely access their audio files without significant delays or computational overhead.

OBJECTS OF THE INVENTION

[0009] The principal object of the present invention is to overcome the disadvantages of the prior art.

[0010] An object of the present invention is to develop a method that is capable of protecting digital audio files from unauthorized access by applying encryption techniques, safeguarding user content against theft and misuse.

[0011] Another object of the present invention is to develop a method that is capable of preserving the original structure of the audio data in a way that prevents tampering or corruption during storage or transmission, ensuring the authenticity of the audio content.

[0012] Another object of the present invention is to develop a method that is capable of employing multiple layers of transformation and randomness to make encrypted data highly resistant to analysis, enhancing overall security.

[0013] Another object of the present invention is to develop a method that is capable of facilitating fast and reliable encryption processes, allowing users to securely access their audio files without significant delays or computational overhead.

[0014] Yet another object of the present invention is to develop a method that is capable of analyzing and confirming the strength of encryption through statistical and visual metrics, ensuring users trust that their audio data is well protected.

[0015] The foregoing and other objects, features, and advantages of the present invention will become readily apparent upon further review of the following detailed description of the preferred embodiment as illustrated in the accompanying drawings.

SUMMARY OF THE INVENTION

[0016] The present invention relates to a method for encrypting a digital audio file that is capable of securing digital audio files through encryption techniques to prevent unauthorized access and ensure the protection of user content from theft and misuse. In addition, the method facilitates fast and reliable encryption processes to enable users to securely access their audio files without significant delays or computational overhead.

[0017] According to an embodiment of the present invention, a method for encrypting a digital audio file, comprising these steps of, analyzing the digital audio file to generate a numerical array data, which includes pre-processing of the digital audio file to extract amplitude, frequency, and waveform characteristics, and converting the digital audio data into a numerical array for encryption, then generating an encryption key, which is undertaken by employing password-based key derivation function 2 (PBKDF2) using a hashed message authentication code (HMAC) based on the secure hash protocol (SHA-256) as the underlying pseudorandom function incorporating randomness (secure random number generation for nonce and salt creation), the derived key is 256 bits, ensuring resistance against brute-force attacks, securing the generated keys using a secure key management module and transforming the numerical array data, which is undertaken iteratively employing sine and cosine functions on numerical audio array to obtain non-linear transformation by introducing confusion and diffusion in the numerical array data, each iteration of non-linear transformation increases security by modifying data patterns, making it resistant to cryptanalysis.

[0018] According to another embodiment of the present invention, the steps further comprising like encrypting the transformed numerical array data, which is undertaken by employing a symmetric, stream cipher. The symmetric, stream cipher generates a stream of pseudo-random bytes (keystream) that is XORed with the plaintext to produce the ciphertext providing high-speed encryption, strong randomness, the encryption uses the derived key and randomness, ensuring message uniqueness and preventing replay attacks, then generating encrypted digital audio file, which is saved in a format that preserves its original structure but makes playback impossible without decryption, after that performing cryptanalysis on the encrypted digital audio file, which is undertaken by employing statistical and visual metrics, the statistical and visual metrics includes histogram, waveform, spectrogram analysis, entropy, correlation coefficient, peak signal-to-noise ratio (PSNR) analysis, signal-to-noise ratio (SNR), number of pixels change rate (NPCR), and unified average changing intensity (UACI) analysis to demonstrate low correlation between original and encrypted files, indicating high randomness and security, then inverse non-linear transformation is applied to reconstruct the original digital audio file.

[0019] While the invention has been described and shown with particular reference to the preferred embodiment, it will be apparent that variations might be possible that would fall within the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
Figure 1 illustrates a flowchart depicting work flow of a method for encrypting a digital audio file.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The following description includes the preferred best mode of one embodiment of the present invention. It will be clear from this description of the invention that the invention is not limited to these illustrated embodiments but that the invention also includes a variety of modifications and embodiments thereto. Therefore, the present description should be seen as illustrative and not limiting. While the invention is susceptible to various modifications and alternative constructions, it should be understood, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims.

[0022] In any embodiment described herein, the open-ended terms "comprising," "comprises,” and the like (which are synonymous with "including," "having” and "characterized by") may be replaced by the respective partially closed phrases "consisting essentially of," consists essentially of," and the like or the respective closed phrases "consisting of," "consists of, the like.

[0023] As used herein, the singular forms “a,” “an,” and “the” designate both the singular and the plural, unless expressly stated to designate the singular only.

[0024] The present invention relates to a method for encrypting a digital audio file that is capable of implementing encryption techniques to prevent digital audio files against unauthorized access, thereby safeguarding user content from theft and misuse. In addition, these existing methods also analyzes and confirms the strength of encryption through statistical and visual metrics in view of ensuring users trust that their audio data is well protected.

[0025] Referring to Figure 1, a flowchart depicting work flow of a method for encrypting a digital audio file is illustrated, comprising these steps of, analyzing 101 the digital audio file to generate a numerical array data, generating 102 an encryption key, transforming 103 the numerical array data, encrypting 104 the transformed numerical array data, generating 105 encrypted digital audio file and performing 106 cryptanalyses on the encrypted digital audio file.

[0026] According to an embodiment of the present invention, the method disclosed herein is developed to protecting digital audio files from unauthorized access by applying encryption techniques, safeguarding user content against theft and misuse. The audio files disclosed herein includes but not limited to WAV files MP3, FLAC, and real-time voice data. The encryption process starts via a detailed analyzing 101 of the digital audio file to generate a numerical array data that involves pre-processing steps where the raw audio data initially stored as discrete time-domain samples is examined to extract meaningful features that characterize the audio signal.

[0027] In an embodiment of the present invention, techniques such as Fourier Transform (e.g., Fast Fourier Transform) are employed to analyze the frequency spectrum, revealing the distribution of frequencies present in the audio. Additionally, amplitude information is derived by assessing the magnitude of the waveform at each sample point, and waveform characteristics like zero-crossing rate or envelope detection are computed. These features collectively provide a comprehensive profile of the audio’s fundamental properties. By capturing these intrinsic characteristics, the process ensures that the subsequent encryption is sensitive to the unique structure of each audio file, thereby enhancing security and robustness.

[0028] Once the key features are extracted, the raw audio data is converted into the numerical array. This transformation involves organizing the amplitude, frequency, and waveform features into a multi-dimensional or linear array format. Essentially, each sample of the audio is represented as a numerical value or set of values, creating a mathematical representation of the original sound.

[0029] The next step involves generating 102 an encryption key for encryption purpose. In an embodiment of the present invention, the process begins with a user providing a password or passphrase intended to serve as the basis for the encryption key. This password is typically a human-memorable string, which, on its own, is not suitable for direct cryptographic use due to its variable entropy and potential predictability. To convert this password into a strong, cryptographically secure key, it first prepares it for processing, which involves normalizing the input removing any inconsistencies such as extra spaces or case differences and then combining it with additional cryptographic elements like a randomly generated salt to enhance security.

[0030] A critical step in this process is the generation of a cryptographically secure salt a random, unique value that is combined with the password during key derivation. The salt ensures that even if two users choose identical passwords, their derived keys differs due to the unique salt values. Additionally, a nonce (number used once) may be generated to prevent replay attacks and ensure that each key derivation instance remains unique. Both salt and nonce are generated using secure random number generators, which provide high-quality entropy, making it computationally infeasible for attackers to predict or reproduce these values.

[0031] Once the salt and user password are prepared, the core of the process involves applying PBKDF2 (Password-Based Key Derivation Function 2). The PBKDF2 works by repeatedly hashing the password combined with the salt using HMAC (Hash-based Message Authentication Code) with SHA-256 as the underlying hash function. This iterative process involves executing many rounds of hashing often thousands or even hundreds of thousands, making the computation time-consuming. The purpose of this iterative hashing is to significantly increase the computational effort required to perform brute-force attacks, thereby strengthening security. Each iteration takes the output of the previous hash as input for the next, creating a chain of computations that substantially delays potential attackers attempting to guess the password by trial.

[0032] After completing the specified number of iterations, the PBKDF2 produces a fixed-length output here, a 256-bit key is suitable for cryptographic operations such as symmetric encryption. This derived key encapsulates the entropy of the password, the randomness of the salt, and the computational effort of the iterative hashing, making it highly resistant to attack. The length and complexity of this key ensure it provides a high level of cryptographic strength, suitable for securing sensitive data. Because the key derivation process is deterministic, the same password, salt, and iteration count always produces the same key, enabling consistent encryption.

[0033] In an embodiment of the present invention, a secure key management module is employed to maintain the confidentiality and integrity of the generated key. This module handles the storage, access, and lifecycle management of cryptographic keys, ensuring they are protected against unauthorized access or disclosure, which includes encrypting the key itself when stored, restricting access through authentication and authorization controls, and implementing secure deallocation practices. Proper key management is essential to prevent key exposure, which may compromise the entire encryption scheme. Through these measures, this process ensures that the derived key remains confidential throughout its lifecycle, supporting secure encryption and decryption operations.

[0034] The next step is transforming 103 the numerical array data, where after generating 102 the key, the numerical array undergoes a series of iterative non-linear transformations. These transformations employ sine and cosine functions applied to the numerical data, introducing a layer of confusion and diffusion core principles in cryptography that obscure the relationship between the plaintext and cipher text. Each iteration modifies the data pattern, making it increasingly complex and less predictable. This non-linear transformation complicates any cryptanalysis attempts by altering the statistical properties of the data and embedding additional layers of security. The iterative nature ensures that each pass amplifies the encryption's robustness, making it resistant to pattern recognition and statistical attacks.

[0035] The primary goal of utilizing sine and cosine functions is to create confusion and diffusion within the data, two core principles identified by Claude Shannon as essential for secure encryption. Confusion refers to making the relationship between the ciphertext and the encryption key as complex as possible, while diffusion aims to spread the influence of each input bit across the output. By applying these non-linear functions, the data pattern becomes highly distorted, ensuring that small changes in the input lead to unpredictable and significant alterations in the output. This transformation effectively masks the statistical properties of the original data, making it difficult for attackers to analyze or reverse-engineer the encryption through pattern recognition.

[0036] The transformation isn't a single application but involves multiple iterations, each one further modifies the data, compounding the complexity introduced. In each iteration, the sine and cosine functions are applied to the current state of the data array, with possible additional operations such as scaling, shifting, or applying the functions to different data segments. As these iterations progress, the data becomes increasingly entangled and non-linear, embedding layers of complexity that are difficult to decipher without the correct key and process sequence. This iterative refinement ensures that the encrypted data does not reveal any obvious patterns, thwarting statistical and differential cryptanalysis attempts.

[0037] The repeated non-linear transformations serve to embed a high level of security within the encrypted data by disrupting any predictable or exploitable patterns. The process alters the statistical distribution of the data, making it resemble random noise and thus resisting attempts to perform pattern recognition or frequency analysis. Moreover, the complexity introduced through multiple iterations ensures that even if an attacker manages to analyze some aspects of the data, reconstructing the original information or deriving the key remains computationally infeasible.

[0038] Once the numerical array has undergone the complex iterative non-linear transformations, the resulting data set is ready for encryption through a symmetric stream cipher. Stream ciphers are cryptographic protocols designed to encrypt data streams bit-by-bit or byte-by-byte, making them particularly well-suited for real-time data such as audio signals. The core mechanism involves generating a pseudo-random keystream a sequence of seemingly random bits that is combined with the transformed data via the XOR (exclusive OR) operation.

[0039] The keystream in this context is generated deterministically from a secret key, which was derived earlier through the password-based key derivation process. Due to the cryptographic strength of the key and the quality of the pseudo-random number generator employed, the keystream appears statistically indistinguishable from true randomness. This pseudo-randomness is critical because it ensures that the encrypted output cannot be predicted or reconstructed without knowledge of the key. The keystream is generated continuously and synchronously with the data stream, enabling seamless encryption and decryption processes.

[0040] The encryption process involves applying the XOR operation between each byte or bit of the transformed numerical array and the corresponding byte or bit of the keystream. This operation produces the ciphertext, which appears as a random sequence of data. Because XOR is its own inverse, the same process is used for decryption: applying XOR between the ciphertext and the identical keystream recovers the original transformed data. This simplicity allows for efficient implementation, optimized for streaming data.

[0041] Stream ciphers are particularly advantageous for audio data because they facilitate high-speed, real-time encryption and decryption. Unlike block ciphers, which process fixed-size blocks and may introduce latency, stream ciphers handle continuous data flows without significant delay. This makes them ideal for live audio transmission, streaming applications, or scenarios where low latency is critical. The lightweight computational requirements further support their use in resource-constrained environments.

[0042] The security of this encryption method hinges on the secrecy and strength of the derived key, as well as the randomness introduced during key generation. Since the keystream depends on these factors, each encryption of the same plaintext even if repeated produces a unique ciphertext. This property, known as message variability or ciphertext uniqueness, prevents replay attacks where an attacker might attempt to reuse captured data to deceive or infiltrate. By ensuring that each encrypted message is different, the process maintains confidentiality and integrity, effectively thwarting many common cryptanalytic techniques.

[0043] After the encryption process is complete and the encrypted digital audio data (denoted as generating 105) has been produced, the next critical step involves storing this data in a manner that ensures both security and compatibility. The goal is to embed the encrypted audio content within a file format that preserves the original structural attributes such as headers, metadata, and formatting information so that the file remains recognizable as a valid audio file by standard media players. Most audio files such as WAV, MP3, or AAC contain specific headers and metadata that describe the file's properties, including sample rate, bit depth, channels, duration, and other relevant information. By embedding the encrypted data within a compatible format, the process ensures that the file retains its structural integrity and handled by existing audio processing tools, media players, or digital management. This approach avoids issues related to incompatible or corrupt files that may arise if raw binary data were stored without adherence to a standard format.

[0044] In a preferred embodiment of the present invention, while maintaining format compatibility, the encryption process effectively "locks" the audio content. The encrypted data appears as nonsensical or random information if opened directly with media players because the core audio data has been transformed and encrypted. Without the correct decryption keys and procedures, the file remains unplayable and indecipherable. This ensures that unauthorized users unable to access or interpret the audio content, providing security against unauthorized playback, copying, or analysis.

[0045] To validate the strength and security of the encryption, the method involves performing 106 extensive cryptanalysis using various statistical and visual metrics. These analyses include histogram analysis to assess the distribution of pixel or sample values, waveform and spectrogram analysis to observe the visual structure, and entropy calculations to measure randomness. Additional metrics such as correlation coefficients evaluate the relationship between original and encrypted data, while Peak Signal-to-Noise Ratio (PSNR) and Signal-to-Noise Ratio (SNR) assess the quality of the encrypted signal. The Number of Pixels Change Rate (NPCR) and Unified Average Changing Intensity (UACI) quantify the degree of change introduced by encryption. Collectively, these metrics demonstrate that the encrypted data exhibits high randomness, low correlation with the original, and strong resistance to statistical attacks, thereby confirming the encryption’s flexibility.

• HISTOGRAM ANALYSIS
Purpose:
Histogram analysis examines the distribution of sample or pixel values within the data, be it audio samples or visual representations like spectrograms. For encrypted data, a uniform histogram indicates that the sample values are evenly spread across the possible range, implying high randomness.
Implication:
A uniform histogram suggests that the encryption effectively removes the statistical patterns inherent in the original data, making it resistant to statistical analysis attacks that rely on frequency distributions.

• WAVEFORM AND SPECTROGRAM ANALYSIS
Purpose:
Visual inspection of waveforms and spectrograms of the original versus encrypted data helps observe the preservation (or lack thereof) of recognizable structures.
Implication:
The original audio or visual signal exhibits distinct patterns or features, while the encrypted version should appear as noise or a random pattern, devoid of any recognizable structure. This visual dissimilarity confirms effective encryption.

• ENTROPY CALCULATION
Purpose:
Entropy measures the degree of randomness or unpredictability in the data. Higher entropy values indicate more randomness.
Implication:
Encrypted data with entropy close to the maximum possible signifies that the data appears highly random, reducing predictability and making cryptanalysis more difficult.
• CORRELATION COEFFICIENT
Purpose:
Correlation coefficients assess the degree of linear relationship between the original and encrypted data.
Implication:
A low correlation coefficient (close to zero) indicates that the encrypted data bears little relation to the original, confirming that the encryption disrupts inherent patterns and features.

• PEAK SIGNAL-TO-NOISE RATIO (PSNR) AND SIGNAL-TO-NOISE RATIO (SNR)
Purpose:
These metrics evaluate the quality of the encrypted data relative to the original, primarily to confirm that the encryption introduces significant distortion.
Implication:
High PSNR and SNR values in the context of encryption imply that the encrypted data is substantially different from the original signal, reflecting effective obfuscation.

• NUMBER OF PIXELS CHANGE RATE (NPCR) AND UNIFIED AVERAGE CHANGING INTENSITY (UACI)
Purpose:
NPCR measures the percentage of data points (pixels, samples) that change when a single bit or pixel in the key or plaintext is altered. UACI quantifies the average change magnitude between the original and encrypted data.
Implication:
High NPCR and UACI values demonstrate that small changes in the key or plaintext produce widespread and significant alterations in the encrypted data, indicating high sensitivity and robustness against differential attacks.

COLLECTIVE SIGNIFICANCE OF THE METRICS
By integrating these various analyses, the evaluation confirms the following critical security properties:
• High Randomness: The encrypted data appears statistically indistinguishable from random noise, as evidenced by histogram uniformity and entropy measures.
• Low Correlation: The minimal relationship between original and encrypted data demonstrates effective disruption of inherent patterns, thwarting pattern-based attacks.
• Resistance to Statistical Attacks: The combined statistical properties indicate that the encrypted data lacks exploitable statistical signatures, making attacks based on frequency analysis or pattern recognition ineffective.
• Strong Sensitivity and Diffusion: Metrics like NPCR and UACI validate that the encryption process propagates small changes widely, ensuring that slight modifications do not compromise security.
• Overall: The comprehensive cryptanalysis confirms that the encryption method offers high security, flexibility, and resilience against various cryptanalytic techniques, affirming its practical applicability in protecting digital audio content.

[0046] Finally, the process includes applying inverse transformations to the encrypted data to enable decryption and reconstruction of the original audio file. This involves reversing the non-linear sine and cosine transformations applied earlier, restoring the numerical array to its pre-encrypted state. Once the inverse transformations are successfully applied, the numerical data converted back into the original audio waveform and structure, allowing playback or further processing. This reversible process ensures that, with the correct decryption key and procedures, the original audio content can be accurately recovered without loss of fidelity, completing the encryption-decryption cycle.

[0047] The present invention works best in the following manner, where the method begins with analyzing 101 the digital audio file to generate the numerical array data. This analysis involves pre-processing the digital audio file to extract key characteristics such as amplitude, frequency, and waveform features, which are then converted into the numerical array suitable for encryption. Next, the encryption key is generated by employing password-based key derivation function 2 (PBKDF2) utilizing the hashed message authentication code (HMAC) based on the secure hash protocol (SHA-256). This process incorporates randomness through secure random number generation for creating the nonce and salt, resulting in the 256-bit derived key that ensures resistance against brute-force attacks. To maintain security, the generated keys are secured using the secure key management module. Following key generation, the numerical array data undergoes transformation through the iterative process employing sine and cosine functions. This non-linear transformation introduces confusion and diffusion into the data, with each iteration modifying the data patterns further, thereby enhancing resistance to cryptanalysis. Once transformed, the numerical array data is encrypted using the symmetric, stream cipher. This cipher produces the stream of pseudo-random bytes (keystream), which is XORed with the transformed data to generate the ciphertext. This approach provides high-speed encryption and strong randomness, with the derived key and randomness ensuring message uniqueness and preventing replay attacks. The encrypted numerical array data is then used to generate the encrypted digital audio file. This file is saved in the format that preserves the original structure of the audio but renders it unplayable without proper decryption. To verify security and robustness, cryptanalysis is performed on the encrypted file using various statistical and visual metrics, including histogram, waveform, spectrogram analysis, entropy, correlation coefficient, peak signal-to-noise ratio (PSNR), signal-to-noise ratio (SNR), number of pixels change rate (NPCR), and unified average changing intensity (UACI). These metrics demonstrate low correlation between the original and encrypted files, indicating high randomness and security. Finally, to reconstruct the original digital audio file, the inverse non-linear transformation is applied, reversing the earlier sine and cosine-based transformations. This process restores the numerical array data to its original form, allowing for playback and use of the audio as intended.

[0048] Although the field of the invention has been described herein with limited reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. , Claims:1. A method for encrypting a digital audio file, comprising:

a. analyzing 101 the digital audio file to generate a numerical array data;

b. generating 102 an encryption key;

c. transforming 103 the numerical array data;

d. encrypting 104 the transformed numerical array data;

e. generating 105 encrypted digital audio file; and

f. performing 106 cryptanalysis on the encrypted digital audio file;

2. The method for encrypting the digital audio file as claimed in claim 1, wherein analysis of the digital audio file includes pre-processing of the digital audio file to extract amplitude, frequency, and waveform characteristics, and converting the digital audio data into a numerical array for encryption.

3. The method for encrypting the digital audio file as claimed in claim 1, wherein generating 102 of an encryption key is undertaken by employing password-based key derivation function 2 (PBKDF2) using a hashed message authentication code (HMAC) based on the secure hash protocol (SHA-256) as the underlying pseudorandom function incorporating randomness (secure random number generation for nonce and salt creation), the derived key is 256 bits, ensuring resistance against brute-force attackssecuring the generated keys using a secure key management module.

4. The method for encrypting the digital audio file as claimed in claim 1, wherein transforming 103 the numerical array data is undertaken iteratively employing sine and cosine functions on numerical audio array to obtain non-linear transformation by introducing confusion and diffusion in the numerical array data, each iteration of non-linear transformation increases security by modifying data patterns, making it resistant to cryptanalysis.

5. The method for encrypting the digital audio file as claimed in claim 1, wherein encrypting 104 the transformed numerical array data is undertaken by employing a symmetric, stream cipher.

6. The method for encrypting the digital audio file as claimed in claim 1, wherein the generated encrypted digital audio file is saved in a format that preserves its original structure but makes playback impossible without decryption.

7. The method for encrypting the digital audio file as claimed in claim 1, wherein performing 106 cryptanalysis on the encrypted digital audio file is undertaken by employing statistical and visual metrics.

8. The method for encrypting the digital audio file as claimed in claim 5, wherein the symmetric, stream cipher generates a stream of pseudo-random bytes (keystream) that is XORed with the plaintext to produce the cipher text providing high-speed encryption, strong randomness, the encryption uses the derived key and randomness, ensuring message uniqueness and preventing replay attacks.

9. The method for encrypting the digital audio file as claimed in claim 7, wherein the statistical and visual metrics includes histogram, waveform, spectrogram analysis, entropy, correlation coefficient, peak signal-to-noise ratio (PSNR) analysis, signal-to-noise ratio (SNR), number of pixels change rate (NPCR), and unified average changing intensity (UACI) analysis to demonstrate low correlation between original and encrypted files, indicating high randomness and security.

10. The method for encrypting a digital audio file as claimed in claim 1, wherein inverse non-linear transformation is applied to reconstruct the original digital audio file.