Cryptomator

Cryptomator is an open-source cross-platform application that provides transparent client-side encryption for files stored in the cloud. It creates encrypted vaults that can be stored on any cloud service that synchronizes with a local directory, ensuring that data is encrypted before it leaves the local device. This approach ensures that the cloud provider never has access to the unencrypted content or the encryption keys.

The software is available as native binaries for Windows, macOS, and Linux. It operates by creating a virtual drive that allows users to interact with encrypted files as if they were on a standard USB flash drive, making the encryption process invisible during daily use. For developers or those preferring to build from source, the application can be cloned and built using Maven and JDK 26.

Key features

• AES encryption with 256-bit key length
• Encryption of file names and obfuscation of folder structures
• Client-side processing with no required accounts or shared data
• Support for any cloud service that synchronizes with a local directory
• Scrypt key derivation and cryptographically secure random numbers
• Authenticated encryption to detect changed ciphertext before decryption
• Support for multiple vaults with individual passwords
• Transactional and atomic I/O operations where supported by the filesystem

The security architecture focuses on minimizing complexity to reduce the attack surface. It employs an unlimited strength policy for keys and ensures that sensitive data is wiped from the heap as soon as possible to prevent memory leaks. Because each file contains the necessary information for its own decryption, the system avoids a single point of failure by eliminating the need for common metadata files that could compromise the entire vault if lost or corrupted.

Cryptomator is designed for users who require privacy and full control over their data when using third-party cloud storage providers. It serves as a security layer that sits between the local filesystem and the cloud synchronization tool.