Our company is implementing the digital signature on invoices. The question I have which I seem to be unable to locate. Are there any ceritifcates or stand alone apps that can actually generate the signature as laid out in the USA at the header and the USA at the trailer. We have EDI software, but are not quite sure on generating the signature and there does not seem to be clear documentation anywhere on creating it. We did look at GS1, and it tells about it, but how do we generate the output to send in the EDI document.
I have to admit that I have not much experience with digital signature but, as far as I know, there is a specific message to transport the digital signature and the information necessary for signature verification by the recipient: the AUTACK(Secure authentication and acknowledgement message).
You can find here message structure and here some interesting samples from EANCOM.