## 3 MuReQua Decentralized Storage and Security Engine (MuReQua DeSSE)
### Main Features of Uploading Component  
Inspired by the works in [13; 31; 32; 33], the core of DeSSE is engineered as a robust and secure platform, dedicated to the efficient management of file storage, uploading, and downloading processes. This platform leverages an innovative approach to data encryption and distribution, maximizing both security and operational efficiency, which is critical for systems handling sensitive information. The system employs a state-of-the-art encryption methodology using AES-256, a standard known for its robustness in the security domain, combined with a private algorithm of cyphering, as we will see. This encryption is complemented by a novel data distribution technique that scatters the encrypted data across a decentralized network, reducing the vulnerability to attacks and failures associated with centralized storage systems. At the upload stage, the system automatically fragments files into multiple encrypted parts. This not only secures the data but also enhances the upload speed by parallelizing the distribution of fragments across the network. This process ensures that the integrity and confidentiality of data are maintained, preventing unauthorized access during transit. Downloads are characterized by a rigorous verification algorithm that ensures data authenticity and integrity. The system includes a powerful decryption engine that swiftly reassembles and decrypts the file fragments. Additionally, as we will see, sophisticated fragment management techniques are employed to efficiently locate and sequence the data fragments, facilitating quick and secure data retrieval. Let us consider the upload model (as in Figure 1). Figure 1: Conceptual upload architecture. This figure illustrates the system flow during the upload process, highlighting key components and operations involved. The upload model is carried out in six steps. 1. A user uploads a file, and the client divides the file into \"n\" fragments and sends the encrypted fragments to the central server, providing additional details such as the file name, type, and size. This initial fragmentation is performed directly on the client device to protect the overall infrastructure and the receiving central server from potential attacks. Furthermore, before transmission, the file undergoes a basic encryption procedure consisting of: 1. Converting the file into a byte array; 2. Randomly generating the number \(n\) of fragments to be created on the client side; 3. Dividing the byte array into \(n\) byte arrays; 4. Encrypting each of the \(n\) byte arrays using AES-256; 5. Transmitting each of the \(n\) encrypted fragments in a scattered and random order to the central server. 2. The central server converts the fragments into a different format from the original and applies AES-256 encryption, then it sends everything to local server 1. Specifically, each individual fragment received undergoes the following process: 1. It is decrypted using AES-256; 2. A basic conversion from the received base (base 10) to a random base with a variable alphabet length in the range of [11; 94] is performed to increase the complexity for a potential attacker targeting the central server, which would encounter fragments with varying bases; 3. The fragment and its base are re-encrypted with AES-256 using a new key generated by the central server; 4. Each fragment is sent to local server 1. 3. Local server 1 carries out the following operations: 1. It decrypts the input data from AES-256; 2. It generates a random number \"mn\" for each fragment; 3. It divides the single fragment into further mn fragments. These sub-fragments are subjected to AES-256 encryption and, in turn, a proprietary encryption follows. A routing table of size n \(\times\) m is generated. 4. Thanks to this proprietary encryption, for each sub-fragment, a \"domain\"-\"path\" pair is generated, where \"domain\" specifies the address of a storage server and \"path\" specifies a logical location where the sub-fragment will be saved.