One solution we came up was to encrypt data before it is submitted and let the user have the private key. The private key is never transferred to our servers. (Generated on browser, kept by the user and used on the browser.)
<a href="http:&#x2F;&#x2F;www.jotform.com&#x2F;encrypted-forms&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.jotform.com&#x2F;encrypted-forms&#x2F;</a>