Can I create a form with a secure sign in?

I would like to assign my customers a password to be able to access the form of my website.  Is this possible?

This is something that can't be done within JotForm for 2 reasons:

1. The most important reason, our Terms of Use. Collecting or asking user credentials in your forms, regardless of the reason, is not allowed.

Here's a snippet:

Phishing. You agree that Company may terminate your JotForm Service immediately if a form's purpose is found to be deceptively obtaining: sensitive credit card information, social security numbers, user login credentials, or other sensitive personal information. All these activities are considered as Phishing and any account along with the violating forms will be suspended immediately.

Collecting Sensitive Information. You may not use the JotForm to collect certain types of sensitive information, including but not limited to credit card information and any type of login credentials. You may collect some sensitive information such as social security numbers or driver’s license numbers, but you are required to use best security practices of JotForm including SSL and Encrypted Forms features. You are solely responsible for compliance with any data protection and privacy laws and rules applicable to the sensitive information.

2. We don't have an option/feature for this and it's mainly because of #1 above.

From how you described it, here's how I would approach it if I'm your developer. I'll set up a page on your website that can't be accessed by anyone unless they have the correct password. Then that's where I will embed the form.

Or I could also just setup a page on your website, and never reveal the link to anyone except those I allow to. And that's where I will embed my form.