CryptSync

CryptSync is a small utility that synchronizes two folders, but the encryption of the content happens in one folder. This means that one of the two folders has all the files in unencrypted form and the other folder has all the files encrypted.

Synchronization works both ways: a change in one folder synchronizes the files to the other folder. If a file is added or modified in the unencrypted folder, it will transfer the file to the other folder where it will already be encrypted and vice versa.