Tarsnap
Updated: 06/30/2017 by Computer Hope
Tarsnap is an encrypted cloud storage service which began operating in 2008. It was developed by Colin Percival, a FreeBSD contributor who got the idea while working on BSD's (Berkeley Software Distribution) version of the tar archive utility.
Tarsnap's client is open source, allowing users to fully examine the code used to encrypt their data. The service features a unique deduplication algorithm, which only uploads data that changed since the last backup. Files are stored on Amazon S3 cloud services, but only the tarsnap user possesses encryption keys to the data, so it's impossible for anyone else to decrypt it.
The Tarsnap client runs on Linux, BSD, macOS, and Windows computers running Cygwin. The service is priced by the gigabyte.