If you’re sending the link by unencrypted means, then the encryption and one-timiness maybe marginally increases the security as compared to an unencrypted email attachment.
- a plaintext email attachment sits around unencrypted on servers, so an attacker who gains access to sender or recipients’ email at any future time, also gains access to the attachment.
- an attachment sent via this service is accessible only to an attacker who downloads the file before the recipient, and they have to be willing to be “noisy” - the link won’t work when the intended recipient tries to download, a detectable condition.
If you’re sending the link by encrypted means, then the encryption is necessary to avoid diminishing security. Attachment file size limits can be so small that they compromise security by forcing people to downgrade security in exchange for larger file sizes (an rock solid secure encrypted email saying “here, I put it on dropbox”) so this can extend the usefulness of those services.
