Simple, secure cloud storage.

Simple Secure Storage Service (S4) is Least Authority's verifiably secure off-site backup system for individuals and businesses.

Free 30-day trial. Then just $25/month (for personal use).

Robustly architected

Even if some servers go down, your data is still safe and available.

Built-in versioning

Easy access to previous revisions of your data.

Scales seamlessly

Built on top of Amazon S3; the future RAIC add-on will support Microsoft Azure, Rackspace, Google Cloud Platform, and HPE Hybrid Cloud as well.

Access control

Users can be given read-only or read-write access to individual files. Files can also be made immutable.

What makes us different?

Unlike most other storage providers, S4 offers verifiable end-to-end encryption.

Learn more about how S4 works

Open source transparency

Unlike other client-side-encryption services, S4 is free, open source software. Anyone can read the code and confirm that it doesn't have secret backdoors; you don't have to just take our word for it.

100% client-side encryption

Unlike many of the popular online services, S4 does client-side encryption on every file. Your data is encrypted before it leaves your device. The server that stores your data can’t spy on your files even if it tries

User Reviews

What our users think about our service.

I was positively amazed about how easy it is to install and how well it works.

Johannes Nix

Wider deployment of this type of file storage system [LAFS] would have an immediate impact on the quality of modern data protection.

Comprehensive National Cybersecurity Initiative (CNCI)

Report on National Cyber Leap Year Summit 2009

If you use only free/libre software, you control your local computing — but using the Internet raises other issues of freedom and privacy, which many network services don't respect. The Simple Secure Storage Service is an example of a network service that does respect your freedom and privacy.

Dr. Richard Stallman

President of the Free Software Foundation

Forthcoming products

Sign up for the latest on our future projects. If you are looking for Magic Folders, we’ve integrated it into S4.


Redundant Array of Independent Clouds (RAIC) will be a multi-cloud add-on to our other products.