I have an external HDD on which i keep most of my personal stuff. I primarily use windows and linux but i also plug it into my android tablet. any software which can run on these platforms will be do.
Im not seeking any FBI level encryption. Might not even be an encryption software. I only need something that can prevent access to my folders in case my drive gets stolen. I tried the NTFS encryption, but that allows you to see contents of the folder, and android doesnt support ntfs anyway.