Memento Cloud, a French data backup solution launched in 2019 by Nathan Richard, uses unused storage space on employees' computers to create a secure, encrypted private cloud. The company claims that roughly 70% of storage on professional computers is unused, and instead of building new cloud infrastructure or using third-party services, Memento Cloud collects this unused space to form a distributed backup system. The technology, protected by a French and European patent, automatically gathers storage from various sources, including workstations, servers, NAS devices, OneDrive, Google Drive, and S3-compatible storage, to build a system similar to RAID principles. Each piece of data is encrypted at the source using algorithms like AES, Curve25519, or Salsa20 before being copied across multiple storage locations. Memento Cloud does not store the decryption keys, ensuring a Zero Trust architecture. The service is hosted in France as a Software as a Service (SaaS) platform and claims to reduce CO2 emissions by 68% compared to traditional data center backups. According to Richard, the founder and president, the idea came from managing backups for his parents' restaurant business, where they struggled with the cost and security of existing cloud solutions. The company aims to provide reliable backup without needing new infrastructure or third-party services. Data is encrypted before being transferred and stored within the company’s existing digital ecosystem, rather than in a third-party data center. The backup process involves installing an agent, which connects to Memento Cloud using an activation code. The agent encrypts data directly on the device before transferring it and replicates it across multiple storage spaces to ensure redundancy. Restoration involves retrieving a copy, decrypting it locally, and restoring it. Memento Cloud never has access to unencrypted data. The system is designed to handle situations where some machines are offline or working remotely by relying on multiple copies stored across different devices. A secure gateway allows devices to remain accessible as long as they have an internet connection. If a machine is turned off, the system uses other available copies for restoration. Data encryption keys, called "trousseaux," are not stored by Memento Cloud, a key part of its Zero Trust model. If a key is lost, the data becomes inaccessible, but the company offers a master enterprise key that can be managed by the IT department or management for recovery. Memento Cloud’s infrastructure, hosted in France, manages the platform’s operations and processes metadata such as backup configurations, task scheduling, equipment availability, copy locations, and access rights. The actual content of the backed-up files remains inaccessible to Memento Cloud. To protect against ransomware attacks, the system continuously monitors storage spaces and detects anomalies. If corruption or deletion is detected, the affected device is isolated, and lost copies are reconstructed elsewhere. For highly distributed organizations, such as EHPAD networks or local government communities, a 100% local mode can be used, treating each location as an independent mini-data center. For others, a hybrid approach combining local and cloud storage is recommended to complicate potential attacks. Memento Cloud supports OneDrive and S3-compatible storage while emphasizing data sovereignty and independence from cloud providers. The company is working toward compliance with the ANSSI recommendations and aims to achieve the CSPN certification, though it is a long-term goal. The 68% CO2 reduction figure is based on Ademe reports comparing the environmental impact of Memento Cloud’s approach to traditional data center backups. For 2026, the company plans to expand its backup capabilities to include virtualized environments such as HyperV and Proxmox.