How secure is Jotform and how do I use the encryption in the form?

How secure is PII when submitting forms?  

How do I use the public and private key?

Choose Jotform to generate a private key for you. The key is needed to decrypt the data. For more information about the encryption, check this guide: https://www.jotform.com/help/344-Encrypted-Forms-and-How-to-Use-Them. There are advantages and disadvantages of this feature. It is important that you'll know it. 

As for the security, our forms are secured by default. All form's submissions are transmitted securely with a 256-bit encryption which means that data is encrypted during the transmission and can't be interrupted by anyone else.

We also have SSL certificate that uses SHA256 with RSA encryption https://www.ssllabs.com/ssltest/analyze.html?d=secure.jotform.com.

I hope that helps.