I have an HTML input <form> with several input fields.
When the user enters appropriate data in the input fields, and clicks "Submit", the input field data must be digitally signed with one of his digital certificates, installed in his Internet Explorer.
The signing must be done from VBScript (if possible), by calling standard functions from the standard MS Windows installation (no additional ActiveX, if possible).
The user certificate with his/her Public key must be included in the signature, everything base64 encoded.
CAPICOM may not be used, as it is deprecated by Microsoft (latest version back in 1997).