Understanding AS2 and AS4: Secure Document Exchange

First, what is AS2?
How is AS4 different?

Understanding AS2 and AS4: Secure Document Exchange

Exchanging business documents in an efficient and secure fashion is crucial in today’s world, and the energy sector, requiring high standards of compliance and data protection, is not exempt from that necessity. At Nominergy, we rely on protocols such as AS2 (Applicability Statement 2) and AS4 (Applicability Statement 4) alongside S/MIME and SMTP to facilitate secure and seamless communication across organizations. How do they work, however?

First, what is AS2?

AS2 is a widely used protocol for securely exchanging EDI (electronic data interchange) and other business documents over the internet. Released in 2002, logically as a follow-up to AS1, AS2 remains one of the most popular standards for B2B communication due to its simplicity, security, and reliability.

AS2 transmits data in a point-to-point manner, meaning it directly connects the sender and the recipient without requiring intermediaries like Value-Added Networks (VANs). It utilizes encryption, digital signatures, and Message Disposition Notifications (MDNs) to ensure that files are securely sent, received, and acknowledged.

It follows a few steps:

Packaging: Documents are wrapped in a secure envelope using S/MIME for encryption and signing.
Transmission: Files are sent over HTTP or HTTPS.
Acknowledgment: The recipient generates an MDN, a receipt confirming successful delivery and integrity of the file.

This ensures AS provides some benefits:

Secure Communication: Encryption and digital signatures protect data in transit.
Direct Connectivity: Eliminates reliance on third-party networks, reducing costs.
Compliance: Meets strict regulatory standards for industries like energy, healthcare, and retail.
Reliability: MDNs provide nonrepudiation, ensuring proof of delivery and integrity.

AS2 is a robust and proven solution for exchanging critical documents like contracts, invoices, and performance reports, particularly in sectors that demand stringent security protocols.

How is AS4 different?

AS4 is an advanced successor to AS2, becoming an ISO standard in 2020 and offering more flexibility and modern features for secure document exchange. Built on web service standards, AS4 is designed for use in both EDI and more dynamic business processes, such as supply chain management or energy trading.

Unlike AS2, which focuses on point-to-point transfers, AS4 operates on a message-exchange model using the ebMS (ebXML Messaging Service) framework. This makes it better suited for asynchronous communication and multi-party interactions.

Its operation is comparable to AS2:

Packaging: Documents are encrypted and signed, similar to AS2.
Message Exchange: Messages are exchanged using SOAP over HTTP or HTTPS, with additional support for attachments and advanced routing.
Reliability: Built-in mechanisms like retries, acknowledgments, and receipts ensure reliable delivery.

AS4 also integrates features such as service agreements, which allow trading partners to specify rules for exchanging messages.

The key benefits it provides are also slightly different:

Modern Architecture: Supports asynchronous messaging, making it ideal for complex workflows.
Scalability: Handles larger message volumes and multi-party exchanges effectively.
Standardization: Compliant with web service standards like SOAP and WS-Security.
Flexibility: Enables richer data exchanges, including attachments and metadata.

While AS2 remains widely used for its simplicity and cost-effectiveness, AS4 is better suited for modern, large-scale applications. Both protocols have their strengths and can be used in complementary ways depending on the business need. Through Nominergy, we integrate AS2 and AS4 into our operations to provide clients with seamless and secure communication. Whether you’re looking to implement AS2 for direct exchanges or AS4 for scalable solutions, our team is here to guide you every step of the way.

In the gas industry, particularly in Denmark and Sweden, there’s an increasing focus on AS4, reflecting a broader industry trend toward modern, secure, and future-proof communication standards. AS4's advantages over AS3 explain why we chose not to provide AS3 as an option at the moment.