How to store the signature image on a secured location ?

Hi,

The customer  needs to store the signature image on a secured location and not make the image URL public.

The signature image is required in the Check Print Report with Remittance advice. (Standard Disbursement Payment File Formats) Report.

Client does not want to provide the signature image for security reason.

But they have agreed if there is any secure method of accessing the image from an external URL that can only be accessed by SaaS environment and cannot be accessed publicly. 

1.) How can we upload(Store) the signature image that would be having an extension of JPEG/PNG/BMP. on the server ?