Cloud Storage Encryption, Explained: Who Really Has Access to Your Files

Every major cloud storage provider will tell you your data is encrypted. And they’re telling the truth — technically. But that word covers a wide range of protections, and the differences matter more than most people realize.

You don’t need to become a security expert. You need to know enough to ask one question: who can access my files besides me?

The three layers of cloud encryption

Most services use some combination of these:

Encryption in transit protects your files while they’re being uploaded or downloaded. This is the lock on the pipe between your phone and the server. Nearly every service does this. It prevents someone from intercepting your files mid-transfer — but it says nothing about what happens after they arrive.

Encryption at rest protects your files while they’re sitting on the server. This means the data on disk is scrambled. If someone physically stole a hard drive from the data center, they’d get gibberish. Good, but incomplete — because the service itself holds the key to unscramble it.

End-to-end encryption (sometimes called zero-knowledge encryption) means your files are encrypted before they leave your device, using a key that only you hold. The service stores scrambled data and has no way to unscramble it. Not the company, not their employees, not anyone.

Most major cloud storage providers use the first two. Far fewer offer the third.

Why the key matters more than the lock

Here’s where it gets important. When a service encrypts your data but holds the encryption key, they can:

• Decrypt your files to scan them, index them, or train AI models
• Expose them if their systems are breached — the attacker gets both the lock and the key
• Change the rules about how your data is used, with a terms-of-service update

This isn’t hypothetical. Cloud providers regularly scan uploaded content for various purposes. Some use your photos to improve image recognition. The encryption exists, but so does the access.

With zero-knowledge encryption, the math is different. The service can’t decrypt your files because it never had the key. A breach exposes scrambled files. There’s nothing to scan, nothing to index, nothing to hand over.

The tradeoff is real: zero-knowledge encryption means the service can’t process your files on its servers. Features like search and organization have to happen on your device instead. And if you lose your encryption key, the service can’t recover your data — because it never had access.

How to evaluate a provider’s encryption claims

If encryption matters to you, here’s what to check:

• “Encrypted” isn’t enough. Ask whether the provider holds the encryption keys or you do. If they hold the keys, your data is protected from external threats but not from the provider itself.
• Look for “zero-knowledge” or “end-to-end” specifically. These terms mean the service can’t access your files. “Encryption at rest” and “in transit” are baseline protections, not privacy features.
• Check if encryption is the default or an option you enable. Some services offer end-to-end encryption but only if you find and toggle the right setting. If it’s not on by default, most users never turn it on. (We wrote more about why defaults matter.)
• Read what happens with your data beyond storage. Some providers use uploaded content for product improvement, advertising profiles, or AI training. Encryption that the provider can bypass doesn’t protect against this.

How we’re approaching this at Abrio

We’re building Abrio with zero-knowledge encryption as the foundation, not a feature you enable. Your photos and videos are encrypted on your device before they’re uploaded. We don’t hold your keys. We can’t see your photos and videos.

That doesn’t mean giving up the features you’d expect from a modern cloud service. Our team’s background in machine learning and large-scale media management means we can build smart organization, search, and categorization that runs entirely on your device — your photos get organized without anyone else needing access.

We also think encryption claims should be verifiable. We’re documenting our approach so you can check the details rather than take our word for it.

If you want cloud storage where encryption isn’t a setting you have to find but the way the system works — that’s what we’re building.