You can achieve the same using AxCrypt app. You can be connected to the external hard disk/drive to your system/laptop, then encrypt your files using AxCrypt app.
AxCrypt is a file encryption software not a Full disk encryption software. AxCrypt has a feature called Secured Folder which provides the convenience to the users, to secure more than one files in a single operation. You can encrypt the Drive/disk folder/file(S) using AxCrypt Secured folder features.
Please note: AxCrypt secured folder is a premium feature.
AxCrypt Secured Folder: — AxCrypt secures files, individually. However, you can designate folders as ‘secured’. The folders will be monitored for new files, and AxCrypt will secure all new files with a single click, or when you sign out.
You can also select multiple files, including all files in a folder, to be secured in a single operation. They still remain individual files, and the folder itself is not secured, just the files in it.
If the file in fact is located in a folder designated as “Secured”, it will soon be re-encrypted again since those folders are monitored for unencrypted files and will encrypt them when you sign out, or click the “Broom” clean up icon.
AxCrypt 2 uses a more robust method for the automatic re-encryption, which sometimes means you as the user have to tell AxCrypt to do it. You’ll see this by the “broom” icon becoming red. This indicates there’s something in need of “clean up”, i.e. re-encryption.
Please check out our video tutorials at https://www.youtube.com/channel/UCoSoXBjq6iCG5232fHoWStA and our other documentation at https://www.axcrypt.net/information/get-started/ to get started with AxCrypt.
Still, if you are facing any issues, please write to Support@axcrypt.net. we are happy to help you.