AS2

AS2, or Applicability Statement 2, is a specification for the secure and reliable exchange of electronic data interchange (EDI) messages over the Internet using HTTP or HTTPS. It defines how two trading partners can exchange EDI payloads, typically in the form of MIME attachments, while ensuring data integrity, confidentiality, and authentication. Security is provided through digital signatures and encryption via S/MIME, and delivery receipts, known as Message Disposition Notifications (MDNs), provide acknowledgments of receipt and non-repudiation.

How it works: The sender builds an EDI document (for example X12 or EDIFACT) and wraps it in a MIME envelope. The payload can be signed and encrypted with X.509 certificates. The message is sent via HTTP POST to the receiver’s AS2 endpoint. The receiver processes the message and returns an MDN, optionally signed, indicating the delivery status. Transport security is typically achieved with TLS, and certificates are used for authentication and for signing/encrypting the payload.

Usage and scope: AS2 is widely used across supply chains in commerce, logistics, and manufacturing to transfer orders, invoices, shipping notices, and other business documents. It supports synchronous and asynchronous receipts, retry logic, and error handling. The protocol has mature tooling and is supported by many enterprise integration platforms.

Relation to standards: AS2 is a standards-based method for EDI over the Internet. It complements other EDI and e‑commerce technologies and is often chosen for its balance of security, reliability, and broad industry adoption. See also EDI, MDN, S/MIME, X.509.