Securely Transmitting Files

Transferring sensitive information is sometimes a necessity. However, sending un-encrypted files via email means that the recipient can forward them and all computers between you and the recipient retain a copy of the email. Cloud services like Dropbox, Google Drive, and others, while great tools for storing data, are not good mechanisms for sharing sensitive information. These services retain backup copies of anything you put on their sites and have no deletion policy, meaning that they can indefinitely hold onto your data,  There are many available methods for securely transmitting files. Instead, it is recommend that you put files containing sensitive information in encrypted zip files as attachments to emails. Since these files require a password to open, they are more secure and only the recipient or others with the password will be able to access them.

The easiest way to send files as encrypted zip files is through a software service. You can download the software, use it to encrypt the files you need to send, and then email it to a recipient. To communicate the password to the recipient, it is recommended that you call them or tell them in person-- do not send the password via email. That email can be forwarded and if you include the password in the same email as the file, the encryption will no longer be useful.

For more technical users, other methods of encrypting zip files include using SFTP, SCP, or other encrypted file transfer protocols. It is also possible to encrypt zip files using SSH and netcat.

What follows is an example workflow for downloading and using a zip file encryption software. In this example, we will use 7zip, a free and open source software.

First, navigate to the 7zip download page and choose the version you would like to use.

After clicking download, you may receive the following prompt. Choose "Run".

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Next, the installation wizard will open. Follow the prompts to install 7zip.

Once the software is installed, open your documents folder and navigate to the document you would like to encrypt. Here, the document is "Creating a Zip File." Right click on the filename and scroll down to the 7zip tab. Mouse over it to open the options and click "Add to Archive." 

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You can now open your email and attack the zip file. Make sure to communicate the password to the recipient by a method other than email.