AS2 (Applicability Statement 2) is a specification for Electronic Data Interchange (EDI) between businesses using the Internet's Web page protocol, the Hypertext Transfer Protocol (HTTP). The specification is an extension of the earlier version, Applicability Statement 1 (AS1). Both specifications were created by EDI over the Internet (EDIINT), a working group of the Internet Engineering Task Force (IETF) that develops secure and reliable business communications standards.
The AS2 standard provides Secure Multi-Purpose Internet Mail Extensions (S/MIME) and uses HTTP or a more secure version, HTTPS, to transmit data over the Internet. AS1 uses a slower protocol, SMTP (Simple Mail Transfer Protocol). The use of HTTP or HTTPS allows communication in real time rather than through e-mail delivery. Security, authentication, message integrity, and privacy are assured by the use of encryption and digital signatures. Another important feature, nonrepudiation, makes it impossible for the intended recipient of a message to deny having received it.
The AS2 standard allows businesses to use a common, single communications solution. This eliminates the complications and costs involved when different businesses in a network use different transfer protocols. A Web server, an EDI transfer engine, and digital certificates are required for data exchange using AS2. Almost any type of data can be transmitted.