Encrypted Cloud Storage
Encrypted cloud-storage services can protect files from unauthorized access, provider employees, server breaches, and compelled disclosure of readable content—depending on how their encryption is implemented.
No cloud service is completely private merely because it uses the word encrypted. Almost every cloud provider encrypts data while it travels over the internet and while it sits on a server. The critical question is:
Who controls the decryption keys?
Two Main Approaches
1. End-to-End or Zero-Knowledge Storage
Files are encrypted on your device before being uploaded, and the provider is not supposed to possess the keys required to decrypt them.
Examples include:
- Proton Drive
- Tresorit
- MEGA
- Sync.com
- Filen
- Internxt
“Zero knowledge” is an industry term, not a universal certification. Each provider implements account recovery, sharing, metadata protection, and key management differently.
2. Client-Side Encryption
You encrypt files yourself before uploading them to an ordinary cloud provider.
The cloud provider stores only encrypted vault data.
Example:
- Cryptomator with Google Drive
- Cryptomator with Dropbox
- Cryptomator with OneDrive
- Cryptomator with iCloud Drive
- Cryptomator with another synchronized storage provider
This separates encryption from storage and gives you more control over the encryption password and software.
Quick Picks
- Best general privacy-focused service: Proton Drive
- Best for businesses and managed teams: Tresorit
- Best for encrypting an existing cloud account: Cryptomator
- Best open-source-focused alternative: Filen
- Simple encrypted storage and sharing: Sync.com
- Large-storage and broad platform support: MEGA
- Alternative privacy suite: Internxt
“Best” depends on your operating system, required storage, collaboration needs, sharing habits, recovery plan, and threat model.
1. Proton Drive
Proton Drive
Type: End-to-end encrypted cloud storage
Proton Drive automatically encrypts file contents, filenames, and folder names before uploading them. Proton says that it cannot access users’ files or names because the necessary private keys remain protected by the user’s account credentials.
Strengths:
- End-to-end encryption enabled by default
- Encrypts filenames and folder names
- Open-source applications and encryption libraries
- Published third-party security audits
- Password-protected sharing links
- Link-expiration options
- Available within Proton’s broader privacy ecosystem
- Apps for major desktop and mobile platforms
Considerations:
- Account information, payment records, IP-related information, storage usage, and certain operational metadata may still exist.
- Some collaboration features remain less extensive than Google Drive or Microsoft 365.
- Using the web application requires trusting the code delivered by Proton during that session.
- A compromised Proton account or unlocked device can expose files.
- Recovery methods must be configured and protected carefully.
Best for: Individuals who want easy encrypted storage integrated with privacy-focused email, calendar, VPN, and password-management services.
See: Proton Drive’s security model
2. Tresorit
Tresorit
Type: End-to-end encrypted cloud storage and collaboration
Tresorit focuses heavily on businesses, professional teams, regulated organizations, and secure file sharing.
Strengths:
- End-to-end encryption
- Encrypts file contents and relevant file metadata
- Granular sharing permissions
- Link expiration and access controls
- Administrative and team-management tools
- Business compliance features
- Device and access management
- Suitable for professional collaboration
Considerations:
- Generally more expensive than consumer-focused alternatives.
- Business administrators may control accounts, policies, and access.
- Organizational recovery and administration features create a different trust model from a purely personal account.
- Its extensive features may be unnecessary for simple personal backups.
Best for: Businesses, legal teams, healthcare organizations, journalists, professional groups, and teams that need encrypted collaboration with administrative controls.
See: Tresorit Security
3. MEGA
MEGA
Type: User-controlled, end-to-end encrypted cloud storage
MEGA encrypts files on the user’s device and provides applications for desktop, mobile, web access, command-line use, synchronization, and sharing.
Strengths:
- Client-side encryption
- Broad platform support
- Large-storage plans
- Fast synchronization and sharing
- Public source code for major applications and its SDK
- File versioning and recovery features
- Widely used and well-established
Considerations:
- MEGA has experienced historical security and ownership controversies, so users should review current audits and documentation.
- Account security depends heavily on a strong, unique password and multifactor authentication.
- Anyone obtaining your session, password, recovery key, or unlocked device may gain access.
- Public or unprotected links can be forwarded.
- Recovery options must be understood before storing important files.
- Large amounts of inexpensive storage should not replace an independent backup.
Best for: Users who need broad platform support and substantial encrypted storage but are comfortable evaluating MEGA’s history and current security model.
See: MEGA’s open-source repositories
4. Sync.com
Sync.com
Type: End-to-end encrypted cloud storage
Sync.com provides encrypted storage, synchronization, file sharing, and team collaboration with a relatively simple interface.
Strengths:
- End-to-end encrypted storage
- Zero-knowledge authentication design
- Sharing controls
- File history and recovery
- Individual and team plans
- Straightforward user experience
- Useful for documents and ordinary file synchronization
Considerations:
- Client applications are not as openly auditable as fully open-source alternatives.
- Interface and synchronization options may feel less advanced than larger mainstream services.
- Account recovery and sharing options should be studied carefully.
- Canadian jurisdiction may matter to some threat models.
- A recipient can save or redistribute any file you share.
Best for: Individuals and small teams wanting straightforward encrypted storage and sharing without managing encryption vaults manually.
See: Sync.com Secure Cloud Storage
5. Filen
Filen
Type: Open-source, end-to-end encrypted cloud storage
Filen is a Germany-based encrypted storage provider offering file synchronization, sharing, notes, collaboration, and other encrypted features.
Strengths:
- End-to-end encryption enabled by default
- Open-source applications
- Client-side encryption
- File and folder sharing
- Desktop and mobile applications
- Privacy-focused service design
- Public technical information and bug-bounty program
Considerations:
- Smaller company and ecosystem than Proton or MEGA
- Fewer years of public operational history than older providers
- Reliability and synchronization should be tested before migrating a large archive
- Users remain responsible for secure passwords, account recovery, and independent backups
- Open-source code does not automatically prove that every distributed build matches the published source
Best for: Users who prioritize open-source clients and want a privacy-focused alternative to larger cloud providers.
See: How Filen describes its encryption
6. Internxt
Internxt
Type: Client-side, end-to-end encrypted cloud storage and privacy suite
Internxt offers encrypted file storage and several additional privacy and security products. It publishes source code and reports having undergone external security reviews.
Strengths:
- Client-side end-to-end encryption
- Open-source applications
- Published security-audit information
- Desktop and mobile support
- File synchronization and sharing
- Based in the European Union
- Broader privacy-service ecosystem
Considerations:
- Smaller ecosystem and operational history than older providers
- Marketing claims about post-quantum protection should be evaluated through current technical documentation rather than slogans alone
- Features and synchronization reliability should be tested before moving critical archives
- Bundled “lifetime” storage plans do not eliminate the need for independent backups
- Open source and an audit do not guarantee the absence of future defects
Best for: Users interested in an open-source European alternative who are willing to test its applications and evaluate its current technical documentation.
See: Internxt’s published security-audit information
7. Cryptomator
Cryptomator
Type: Open-source client-side encryption tool
Cryptomator creates an encrypted vault that can be stored inside almost any ordinary cloud-synchronized folder. Files are decrypted through a virtual drive when the vault is unlocked.
Works with services such as:
- Google Drive
- Dropbox
- Microsoft OneDrive
- iCloud Drive
- pCloud
- Nextcloud
- Syncthing
- External drives
- Network storage
Cryptomator encrypts:
- File contents
- File names
- Folder names
- Directory structure
The storage provider can still observe information such as the existence of the vault, approximate encrypted file sizes, upload activity, modification times, account details, and network connections.
Strengths:
- Open source
- Independent of any one cloud provider
- You control the vault password
- Encrypts filenames and folder structure
- Works with existing storage accounts
- No separate Cryptomator storage subscription required
- Installer signatures are available for verification
Considerations:
- Slightly more complicated than an integrated encrypted drive
- Losing the vault password and recovery key may make the data unrecoverable
- A vault must be unlocked before files can be used normally
- Malware can read files while the vault is unlocked
- Decrypted files exported outside the vault are no longer protected by Cryptomator
- Simultaneous edits from multiple devices may cause synchronization conflicts
- Vault corruption or accidental cloud deletion remains possible
Best for: Users who already use a mainstream cloud provider but do not want that provider to read their files.
See:
How to Choose
If you want encrypted storage that “just works”
Consider:
- Proton Drive for personal use
- Tresorit for businesses and managed teams
- Sync.com for straightforward storage and sharing
- Filen for an open-source-focused alternative
If you already use Google Drive, Dropbox, OneDrive, or iCloud
Use:
- Cryptomator + your existing provider
The provider stores the encrypted vault while Cryptomator manages encryption locally.
If you need substantial storage
Compare:
- MEGA
- Filen
- Proton Drive
- Internxt
Storage prices and plan limits change frequently. Do not choose solely by advertised capacity.
If you frequently collaborate with teams
Compare:
- Tresorit
- Proton Drive
- Sync.com
- Filen
Confirm whether shared documents, comments, previews, permissions, and account recovery maintain the encryption properties your organization requires.
Metadata That May Remain Visible
End-to-end encryption can hide file contents while leaving other information available to the provider, depending on the service:
- Account email address
- IP addresses
- Login times
- Device information
- Payment records
- Total storage usage
- File sizes or approximate sizes
- Upload and download timing
- Sharing activity
- Recipient accounts
- Failed login attempts
- Support communications
Read the provider’s privacy policy and technical security documentation to determine what it retains.
Secure Sharing
Encrypted storage does not make every sharing method safe.
Before sharing a file:
- Confirm the recipient through a separate trusted channel.
- Use a strong sharing password when supported.
- Send the password through a different communication channel.
- Set an expiration date.
- Limit downloads or access where supported.
- Remove the link when it is no longer needed.
- Avoid placing sensitive information in the link’s filename or message.
- Assume that an authorized recipient can save, copy, photograph, or redistribute the file.
A link protected by end-to-end encryption can still be compromised if the entire link or its password is sent to the wrong person.
Account and Recovery Security
For any encrypted storage service:
- Use a long, unique password.
- Store it in a trusted password manager.
- Enable strong multifactor authentication.
- Prefer a security key or passkey when supported.
- Save recovery codes offline.
- Protect any recovery key separately from the cloud account.
- Review connected devices and sessions.
- Remove old or unknown devices.
- Keep the storage application and operating system updated.
- Verify downloads and signatures when provided.
With a genuine zero-knowledge design, the provider may be unable to recover your files if you lose every usable password, recovery key, and authenticated device.
That inconvenience is partly a consequence of the provider not possessing a master decryption key.
Cloud Storage Is Not a Complete Backup
Synchronization can reproduce mistakes across every connected device. If ransomware encrypts files, an account is deleted, or a synchronized folder is emptied, those changes may propagate to the cloud.
Use the 3-2-1 backup principle:
- Keep at least three copies of important data.
- Store them on at least two different types of media or systems.
- Keep at least one copy separate or offline.
For example:
- Encrypted cloud copy
- Encrypted external drive
- Separate offline backup stored safely elsewhere
Periodically test whether your backups can actually be restored.
Important Limitations
Encrypted cloud storage does not protect against:
- Malware running on your device
- An attacker using your unlocked account
- Screen capture or keylogging
- Weak or reused passwords
- Stolen recovery codes
- Files opened outside the encrypted vault
- A malicious recipient
- Accidental deletion without usable version history
- Physical access to an unlocked device
- Unencrypted temporary files created by another application
Encryption protects data only within the boundaries covered by its design.