TrueCrypt
Open Source
TrueCrypt is an open source software to encrypt volumes of data. It even supports the creation of virtual encrypted volumes which is portable.
EncFS
Open Source
EncFS is a Free (LGPL) FUSE-based cryptographic filesystem. It transparently encrypts files, using an arbitrary directory as storage for the encrypted files.
Cryptomator
Open Source
Cryptomator is a multi-platform transparent client-side encryption of your files in the cloud.
Boxcryptor
Freemium
Boxcryptor protects your data in the cloud with end-to-end encryption.
Compare Sookasa with alternatives
Compare Cryptomator and Sookasa and decide which is most suitable for you.