Utility for online file encryption?

Question

Encryption

Colleagues, tell me, please, on this issue. There is a simple task - to store the project folder in the cloud, for example, in DropBox. Everything is fine, but some files in this folder should be protected even more than the usual DB authorization system. The solution comes to mind - to use some utility for online encryption. You save the file in a folder that is synchronized with the cloud storage, the utility intercepts the save signal and puts an already encrypted file in the local directory, which is synchronized with the cloud.
Tell me, what utility of this kind is best to use for greater security?
Addition : operating system - Windows 7.

Answer 1

Since you did not say what OS you are talking about, I will answer that I used encfs for this. I mounted the encrypted subfolder in dropbox to a normal directory and worked with it.
They say TrueCrypt copes with this task.

Answer 2

https://www.boxcryptor.com/