AS2:     Applicability Statement 2 (this document) and [RFC4130]; see RFC 2026
            [RFC2026], Section 3.2

   EDI:     Electronic Data Interchange

   EC:      Electronic Commerce (often referred to as Business to Business, B2B).

   B2B:     Business to Business

   Receipt: The functional message that is sent from a receiver to a
            sender to acknowledge that an EDI/EC interchange has been
            received. This message may be either synchronous or asynchronous
            in nature.

   Signed Receipt: A receipt with a digital signature.

   Synchronous Receipt: A receipt returned to the sender over the same
            TCP/IP connection as the sender's original message.

   Asynchronous Receipt: A receipt returned to the sender over a different
            TCP/IP connection than the sender's original message.

   Message Disposition Notification (MDN): The Internet messaging format
            used to convey a receipt. This term is used interchangeably
            with receipt. An MDN is a receipt.

   Non-repudiation of receipt (NRR): A "legal event" that occurs when
            the original sender of an signed EDI/EC interchange has
            verified the signed receipt coming back from the receiver.
            The receipt contains data identifying the original message
            for which it is a receipt, including the message-ID and a
            cryptographic hash (MIC). The original sender must retain
            suitable records providing evidence concerning the message
            content, its message-ID, and its hash value. The original
            sender verifies that the retained hash value is the same as
            the digest of the original message, as reported in the
            signed receipt. NRR is not considered a technical message,
            but instead is thought of as an outcome of possessing
            relevant evidence.

   S/MIME:  A format and protocol for adding cryptographic signature
            and/or encryption services to Internet MIME messages.

   Cryptographic Message Syntax (CMS): An encapsulation syntax used to
            digitally sign, digest, authenticate, or encrypt arbitrary
            messages.

   SHA-1:   A secure, one-way hash algorithm used in conjunction with
            digital signature. This algorithm is retained for backward
            compatibility but is deprecated in this specification.
            Implementations MUST support SHA-256 or stronger where possible,
            and SHOULD prefer these algorithms in production environments
            unless legacy partners cannot yet migrate to SHA-256 or stronger.

   MD5:     A secure, one-way hash algorithm used in conjunction with
            digital signature. This algorithm is obsolete and MUST NOT be generated
            by conformant implementations.

   MIC:     The Message Integrity Check (MIC) is a cryptographic method used
            to verify that a message has not been altered or tampered with during
            transmission or storage, ensuring the data is trustworthy and complete.
            It works by generating a unique hash value from the message's contents,
            which is then transmitted with the message. The recipient recalculates
            the hash on the received message and compares it to the provided MIC;
            if they don't match, the message is discarded, indicating it was modified.

   User Agent (UA): The application that handles and processes the AS2 request.