I have a lot of experience in downloading the raw data from Ancestry DNA. Basically - in order to access and compare your raw data, you first need to upload this raw data to Gedmatch.com
If you want to compare your Ancestry DNA test results with your husband's Ancestry DNA test results, you will first need to download your raw data folder and your husband's raw data folder from Ancestry DNA. Then - you need to upload your folder and your husband's folder to Gedmatch, which allows you to run a "one-to-one" comparison between your test and your husband's test.
Here is the message that I send to many of my Ancestry DNA matches to explain how to download and access your raw data folder and upload to Gedmatch. Let me know if you have any questions.
Gedmatch is only used to compare the raw data from your Ancestry DNA test with the raw data from other people who have uploaded the results of their autosomal DNA tests. Ancestry DNA, Family Tree DNA and 23andme each offer autosomal DNA tests. Gedmatch allows you to compare your results from any of these tests. Gedmatch.com is a free site that has more advanced comparison tools and would allow us to see if there are others in the Gedmatch database who match in the same DNA location.
As far as the site's security goes, I am not a computer expert, so I can't speak to the overall site security. It is rather anonymous though, in that you choose your username and the email that you want to link to your test. I use a standard outlook.com email address that I only use for genealogy and variations of the username Steelerfan.
Here are the basic instructions on how to upload your test results to gedmatch. As far as Gedmatch goes, if you want to upload your DNA results there, you first need to upload your raw DNA from Ancestry DNA in order to use the advanced DNA comparison tools on Gedmatch. You have to download your raw DNA from your Ancestry DNA profile - which you do by going to your DNA Homepage on Ancestry and then click "Settings" underneath your test name. This takes you to your Ancestry DNA settings page. On the right you will see an option to "Download your raw DNA data". Just click the "Get Started" button to access and then download your raw data (which will be placed into a folder on your computer). You then select this folder when uploading your Ancestry DNA to Gedmatch. After you have your raw DNA downloaded, go back to Gedmatch.com, and go to the top right corner in the "File Uploads" section and click on Ancestry.Com, which will then take you to a screen that will allow you to enter your raw DNA from Ancestry.
Let me know if you have any questions.