Digital Signing guidelines - NatWest

2. Overview of Digital Signing Solutions
All communications between the customer and the Bankline Direct service in either direction must be secure.
All transmissions generated by the service will be digitally signed; likewise any payment messages or files sent
to the Bankline Direct service must be signed with a digital certificate.
Section 5 details the security configuration applied to reports and acknowledgements generated by the Bankline
Direct service.
Customer utilising the payment submission service must send messages and files complying with the prescribed
NatWest security and industry standards. There are two options for applying a digital signature to payment
transmissions, Smartcards and Hardware Security Module (HSM), please refer to sections 6 and 7 respectively.
An HSM solution offers an unattended solution for straight through processing and may be attractive to customers
who process large volumes of payments. An HSM solution reduces the administrative overhead and associated
staffing needs but is a more expensive option. It is the customer’s responsibility to procure and install an
HSM module.
A Smartcard solution is a secure, but manual process requiring intervention from staff members, by entering a
PIN number using a card reader and individual card credentials. This Smartcard option is considerably cheaper.
Bankline Direct transmissions are digitally signed using an HSM.
Digitally signed communications that travel in both directions adhere to the S/MIME standard.
Section 3 provides a high level description of S/MIME.
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