Digital Signature in asp.net page

Question

We have a letter writing software writtein in ASP.net hosted on cloud. It is used by lawyers to write letters.

Lately the users have received digital signature from some government agency on a CD, that identifies them uniquely. Now they want to sign each letter they write on the web in our software with this digital signature.

Is this technically even possible? Can someone please give me some direction on what this entails?

Tx

Answer 1

Larry's answer is good only if you are implementing it From Scratch and also if you have total control over the end users. In Order to use Individual Token, you must use a third party Interface(From any Certificate Authorities Preferably) to Sign the document from the End User Token/CD DSC. This Solution will work for certificates from multiple CA's ,so end users with existing certificate can digitally Sign any PDF Document. We have implemented such kind of Solution for Government Agencies and is Very feasible.

Answer 2

You can either roll a solution yourself or use an off the shelf solution such as the CoSign Central digital signature appliance from DocuSign (my company)

Note that if you decide to roll your own solution, you must ensure that the signer has sole control over their private key. (Presumably what is included on the CDs that you received.)

This is another aspect of using a SSCD (Secure Signature Creation Device) for creating the signature.

Bottom line: for using X.509 digital certificates to digitally sign documents on behalf of person, the entire system must meet the legal requirements for a digital signature system (US terminology). In Europe and elsewhere, this called an Advanced or Qualified Electronic Signature system, depending on the source of the root cert of the signer's cert.

This is different than code signing, signing SSL requests and other uses of X.509 digital certificates.