# Managing Access to Confidential Documents: A Case Study of an Email Security Tool
## 2 Background  
### Virtru  
Virtru is an end-to-end encryption platform that encrypts Gmail messages, attachments, and files stored on Google Drive, including Google Docs, Google Sheets, and Google Slides [12]. Virtru's simple Chrome extension keeps emails and files secure in Google Workspace, preventing Google and unauthorized parties from accessing information. Recipients can read a Virtru encrypted email without Virtru installed. Virtru uses a secure reader platform that allows users to access it right in their web browser by clicking on the Unlock Message button in their Virtru secure email. Upon verifying that they are an authorized recipient of that email or file, they can read and reply to the secure email directly from their browser.  
In addition to encrypting messages and attachments, the security options of Virtru (see Figure 1) allow users to perform the following tasks:  
* Add persistent file protection (PFP) to the encrypted file: This feature restricts access to only authorized users, even if it is shared or downloaded. New (unauthorized) users are allowed to request access to a file, and they will be forced to authenticate in their web browser prior to seeing the secure file in Virtru's Secure Reader. If someone requests access to a file that a user owns, then the recipient will receive an email notification from Virtru. Unauthorized users will not be granted access.
* Set an expiration date for an encrypted email or file: Users can restrict access after a particular point in time. If a recipient tries to access the content after its expiration, then they will receive a prompt indicating their access has expired. Expiration can also be managed after an email has been sent.
* Disable forwarding: This ensures that the recipients can access the encrypted content but will stop any additional users from gaining access to the message. If the original recipient sends the email to a new party, then the new user will not be added as an authorized user and will not be able to unlock the message.
* Add watermarking to a secure file: Recipients will only have access to content inside the Secure Reader, and their email addresses will be watermarked across the document. This feature prevents the recipient from downloading the file and keeping a local copy.
* Revoke (or reauthorize) access: Virtru even allows the sender to revoke access to specific recipients granularly at any time. If recipient access is revoked, then users will receive a prompt indicating their access has been removed.  
Various universities and companies in the US utilize Virtru [14; 15], allowing them to add an extra layer of security to their email messages. While Virtru works for a few email providers, it does not work with all web applications [16]. Furthermore, Virtru's private keys are associated with each device, and thus they cannot be used across devices. It also relies on a centralized server to verify that users own their respective email addresses and deliver private keys [17]. However, it uses a distributed architecture for unique symmetric key generation for each email [18]. By keeping content and encryption keys separate, only authorized parties are able to access unencrypted content, making it impossible for Virtru to decrypt user content [18]. In this way, data are kept private, even from Google or unauthorized parties. Although Virtru provides email transmission security, it does not protect against email accounts becoming compromised [19]. Therefore, Virtru offers secure encryption alternatives to portal-based encryption technologies. With these technologies,  
Figure 1: Virtru’s email composition window along with its message security options.  
data can be encrypted, but this necessitates the use of separate systems by the recipient and the user [20]. This set-up may grant vendors access to their data, potentially introducing the risk of data breaches.