This protocol enables a protocol client to communicate with a protocol server over a Hypertext Transfer Protocol (HTTP) connection to apply a digital signature to a form file that is stored on the protocol server. To apply a digital signature to a form file stored on the protocol server, the protocol client performs the following supported functions:
Retrieve Form File Hash: The protocol client sends this message to the protocol server to initiate the application of a digital signature to a form file. Using this protocol function, the protocol client sends a request to the protocol server that contains local information, including a rendered image of the form file and operating system information, to be embedded in the signed form file. The protocol server sends back an HTTP response containing a digest of the local information sent by the protocol client, and other data stored in the form file. See section 5.1 for security considerations.
Add Signature Value and Context: Using this protocol function, the protocol client generates encrypted ciphertext of the digest value returned in the HTTP response to the Retrieve Form File Hash request message. The ciphertext value, and the certificate used to encrypt it, are sent to the protocol server and stored in the form file as value and context, respectively, of the digital signature. The application of the digital signature is complete when the protocol server successfully processes this request. See section 5.1 for security considerations.
Cancel Digital Signature: Using this protocol function, the protocol client sends an HTTP request to the protocol server to notify the protocol server that the signing process has been cancelled.