Digital Signature Solution in Siebel CRM invoice

Need help of CRM developer who can develop digital signature solution for Siebel CRM invoice form. The digital signature is in class 2 type token. We need full automotion such that after generating the invoice in web client,if user presses enter,it should ask for the password for digital signature. Upon giving the correct password,it should sign. Then the same signed invoice gets stored in the Siebel system and it can be used by [login to view URL] download into PDF and then signing is allowed.