Cryptomator VS Bouncy Castle

the best way to do this is with https://cryptomator.org

Before putting anything on a cloud service I would recommend 3rd party tools, like Cryptomator, to encrypt folders and such, then upload to a cloud service.

I use Cryptomator - https://cryptomator.org

I've used countless encryption "schemes" over the years, from True/Vera-Crypt to encrypted sparse bundles/images, and none have ever really felt right.

These days i tend to use Cryptomator[0] instead. It accomplishes what none of the others could do, which is transparent encryption across devices.

With Cryptomator, i simply create a vault somewhere in the cloud, stuff data in it, and i can access it from my laptop, phone or tablet, and not think much about it. It integrates into the normal file browsing APIs, and doesn't get in the way.

Because it does "per file" encryption, it also doesn't need to download a 20-100MB chunk from the cloud before decrypting, so it's rather fast (depending on file size of course).

[0]: https://cryptomator.org/

Cryptomator's arguably the most popular encryption software for cloud storage (you can give yourself zero-knowledge encryption by using them) - it's actually what they specialize & focus on (cloud encryption). It's 100% open source and Free to use on computers. On phones I believe it's just a 1-time fee of a few bucks ($13-14, then you have it forever) - note: their iOS offering is still new, so may be a bit unpolished at the moment.

This is the solution: https://cryptomator.org/

Cryptomator. It is made for uploading files securely to cloud storage, but works locally, is easy to use, and completely free for your use case.

Note that there may be incompatibilities until NIST has published the final revisions. Some specifications are on Round 3 kyber, others are on FIPS 203.

This one will interoperate with Bouncy Castle as we both use FIPS 203 draft, but won't interoperate with OQS that is still on the Round 3 submission.

See also: https://github.com/bcgit/bc-java/issues/1578

The readme mentions a dependency on Bouncy Castle - note that BC already contains several Java-based PQC signature schemes, see https://doc.primekey.com/bouncycastle/interoperability#Inter... and https://github.com/bcgit/bc-java

The best official resources are probably the example classes in the bouncycastle repository. They give you a rough idea for how to use the API, although they are a bit minimal unfortunately. You can probably apply a lot of domain knowledge (what algorithms are good/bad) from openpgpjs too, although you'd have to find out how the respective method calls are called on the BC side.

Why? Bouncy Castle has all you need.

Cryptography? Use Java Cryptography Extensions and Java Secure Socket Extensions with Bouncy Castle

Recently there was a constant time enhancement in bouncy castle that added a comparison using indexOf instead of charAt. Fairly easy to overlook, although glaring in hindsight, if there are no negative tests covering the functionality.