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INTERNET-DRAFT                                    D. Moberg
draft-ietf-ediint-as2-20.txt                      R. Drummond
Category: Standards Track                         21 December 2004
Expires: May 2005

                      MIME-based Secure Peer-to-Peer
                   Business Data Interchange Using HTTP,
                      Applicability Statement 2 (AS2)

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
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   http://www.ietf.org/1id-abstracts.html

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IPR Statement

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.





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 Abstract

   This document provides a applicability statement (RFC 2026, 3.2)
   that describes how to exchange structured business data securely
   using the HTTP transfer protocol, instead of SMTP; the
   applicability statement for SMTP is found in RFC 3335. Structured
   business data may be XML, Electronic Data Interchange
   (EDI) in either the American National Standards Committee (ANSI)
   X12 format, or in the UN Electronic Data Interchange for
   Administration, Commerce and Transport (UN/EDIFACT) format,
   or in other structured data formats. The data is packaged using
   standard MIME structures. Authentication and data confidentiality
   are obtained by using Cryptographic Message Syntax with S/MIME
   security body parts. Authenticated acknowledgements make use of
   multipart/signed Message Disposition Notification (MDN)
   responses to the original HTTP message. This applicability
   statement is informally referred to as "AS2" because it is the
   second applicability statement, produced after "AS1," RFC 3335.

   Feedback Instructions:

   NOTE TO RFC EDITOR:  This section should be removed by the RFC editor
   prior to publication.

   If you want to provide feedback on this draft, follow these
   guidelines:

   -Send feedback via e-mail to the ietf-ediint list for discussion,
   with "AS#2" in the Subject field. To enter or follow the discussion,
   you need to subscribe to ietf-ediint@imc.org.

   -Be specific as to what section you are referring to, preferably
   quoting the portion that needs modification, after which you state
   your comments.

   -If you are recommending some text to be replaced with your suggested
   text, again, quote the section to be replaced, and be clear on the
   section in question.






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   Table of Contents

   1.0 Introduction
        1.1 Applicable RFCs..........................................4
        1.2 Terms ...................................................4
   2.0 Overview .....................................................5
        2.1 Overall operation .......................................5
        2.2 Purpose of a security guideline for MIME EDI ............6
        2.3 Definitions .............................................6
        2.4 Assumptions .............................................7
   3.0 Referenced RFCs ..............................................9
        3.1 RFC 2616 HTTP v1.1 ......................................9
        3.2 RFC 1847 MIME Security Multiparts .......................9
        3.3 RFC 3462 Multipart/report ...............................9
        3.4 RFC 1767 EDI Content ....................................9
        3.5 RFC 2045, 2046, 2049 MIME ..............................10
        3.6 RFC 3798 Message Disposition Notification ..............10
        3.7 RFC 3851, 2630 S/MIME Version 3 Message Specifications..10
        3.8 RFC 3023 XML Media Types ...............................10
   4.0 Structure of an AS2 message .................................10
        4.1 Introduction ...........................................10
        4.2 Structure of an Internet EDI MIME message ..............10
   5.0 HTTP Considerations .........................................11
        5.1 Sending EDI in HTTP Post Requests ......................11
        5.2 Unused MIME Headers and Operations .....................12
        5.3 Modification of MIME or other headers...................12
        5.4 HTTP Response Status Codes .............................13
        5.5 HTTP Error Recovery ....................................14
   6.0 Additional AS2 Specific HTTP Headers ........................14
        6.1 AS2 Version Header .....................................14
        6.2 AS2 System Identifiers .................................15
   7.0 Structure and Processing of an MDN Message ..................16
        7.1 Introduction ...........................................16
        7.2 Synchronous and Asynchronous MDNs ......................18
        7.3 Requesting a Signed Receipt ............................19
        7.4 MDN Format .............................................23
        7.5 Disposition Mode, Type, and Modifier ...................28
        7.6 Receipt Reply Considerations in a HTTP Post  ...........32
   8.0 Public Key Certificate Handling .............................33
   9.0 Security Considerations .....................................34
   10.0 IANA Considerations ........................................36
        10.1 Registration...........................................36
   11.0 Acknowledgements ...........................................36
   12.0 References .................................................37
        12.1 Normative References ..................................37
        12.2 Informative References ................................38
   13.0 Authors' Addresses .........................................38

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   Appendix ........................................................39
   A. Message Examples .............................................39






   1.0 Introduction

   1.1 Applicable RFCs

   Previous work on Internet EDI focused on specifying MIME content
   types for EDI data [2] and extending this work to support secure
   EC/EDI transport over SMTP [4].  This document expands on RFC 1767 to
   specify a comprehensive set of data security features, specifically
   data confidentiality, data integrity/authenticity, non-repudiation of
   origin and non-repudiation of receipt over HTTP.  This document also
   recognizes contemporary RFCs and is attempting to "re-invent" as
   little as possible.  While this document focuses on EDI data, any
   other data types describable in a MIME format are also supported.

   Internet MIME based EDI can be accomplished by using and complying
   with the following RFCs:

     o  RFC 2616 Hyper Text Transfer Protocol
     o  RFC 1767 EDI Content Type
     o  RFC 3023 XML Media Types
     o  RFC 1847 Security Multiparts for MIME
     o  RFC 3462 Multipart/Report
     o  RFC 2045 to 2049 MIME RFC's
     o  RFC 3798 Message Disposition Notification
     o  RFC 3851, 3852 S/MIME v3.1 Specification

   Our intent here is to define clearly and precisely how these are used
   together, and what is required by user agents to be compliant with
   this document.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL   NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [13].

   1.2 Terms

   AS2 - Applicability Statement 2 (this document)


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   EDI - Electronic Data Interchange

   EC - Business to Business Electronic Commerce

   B2B - Business to Business

   Receipt - The functional message that is sent from a receiver to a
   sender to acknowledge receipt of an EDI/EC interchange. 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 during the
   same HTTP session as the sender's original message.

   Asynchronous Receipt - A receipt returned to the sender on a
   different communication session than the sender's original message
   session.

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

   Non-repudiation of receipt (NRR) - NRR is 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 to be 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.

   CMS - Cryptographic Message Syntax (CMS) is 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 is the recommended algorithm for AS2.

   MD5 - A secure, one-way hash algorithm used in conjunction with
   digital signature. This algorithm is allowed in AS2.

   MIC - The message integrity check (MIC), also called the message
   digest, is the digest output of the hash algorithm used by the

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   digital signature. The digital signature is computed over the MIC.

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

   2.0 Overview

   2.1 Overall Operation

   A HTTP POST operation [3] is used to send appropriately packaged EDI,
   XML, or other business data. The Request-URI ([3], section 9.5)
   identifies a process to unpack and handle the message data and to
   generate a reply for the client that contains a message disposition
   acknowledgement (MDN), either signed or unsigned. The MDN is either
   returned in the HTTP response message-body or by a new HTTP POST
   operation to a URL for the original sender.

   This request/reply transactional interchange can
   provide secure, reliable, and authenticated transport for
   EDI or other business data using HTTP as a transfer protocol.

   The security protocols and structures used also support auditable
   records of these document data transmissions, acknowledgements and
   authentication.

   2.2 Purpose of a security guideline for MIME EDI

   The purpose of these specifications is to ensure interoperability
   between B2B Electronic Commerce user agents, invoking some or all of
   the commonly expected security features. This document is also NOT
   limited to strict EDI use, but applies to any electronic commerce
   application where business data needs to be exchanged over the
   Internet in a secure manner.

   2.3 Definitions

   2.3.1 The secure transmission loop

   This document's focus is on the formats and protocols for exchanging
   EDI/EC content securely in the Internet's HTTP environment.

   The "secure transmission loop" for EDI/EC involves one organization
   sending a signed and encrypted EDI/EC interchange to another
   organization, requesting a signed receipt, followed later by the
   receiving organization sending this signed receipt back to the
   sending organization.  In other words, the following transpires:

        o  The organization sending EDI/EC data signs and encrypts the
           data using S/MIME. In addition, the message will request a
           signed receipt to be returned to the sender of the message.

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           To support NRR, the original sender retains records of the
           message, message-ID, and digest (MIC) value.
        o  The receiving organization decrypts the message and verifies
           the signature, resulting in verified integrity of the data
           and authenticity of the sender.
        o  The receiving organization then returns a signed receipt
           using the HTTP reply body or a separate HTTP POST operation
           to the sending organization in the form of a signed message
           disposition notification.  This signed receipt will contain
           the hash of the received message, allowing the original
           sender to have evidence that the received message was
           authenticated and/or decrypted properly by the receiver.

   The above describes functionality which, if implemented, will satisfy
   all security requirements and implement non-repudiation of receipt
   for the exchange. This specification, however, leaves full
   flexibility for users to decide the degree to which they want to
   deploy those security features with their trading partners.

   2.3.2 Definition of receipts

   The term used for both the functional activity and the message for
   acknowledging delivery of an EDI/EC interchange is receipt or signed
   receipt.  The term is used if the acknowledgment is for an
   interchange resulting in a receipt which is NOT signed.  The second
   term is used if the acknowledgment is for an interchange resulting in
   a receipt which IS signed.

   A term often used in combination with receipts is non-repudiation of
   receipt.  NRR refers to a legal event which occurs only when the
   original sender of an interchange has verified the signed receipt
   coming back from recipient of the message, and has verified that
   the returned MIC value inside the MDN matches the previously
   recorded value for the original message.

   NRR is best established when both the original message and the
   receipt make use of digital signatures. See also the Security
   Considerations section for some cautions regarding NRR.

   For information on how to format and process receipts in AS2, refer
   to section 7.

   2.4 Assumptions

   2.4.1 EDI/EC process assumptions

   o  Encrypted object is an EDI/EC Interchange

   This specification assumes that a typical EDI/EC interchange is the
   lowest level object that will be subject to security services.


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   Specifically, in EDI ANSI X12, this means that anything between, and
   including segments ISA and IEA, is secured. In EDIFACT, this means
   anything between, and including, segments UNA/UNB and UNZ is secured.
   In other words, the EDI/EC interchanges including envelope segments
   remain intact and unreadable during fully secured transport.

   o  EDI envelope headers are encrypted

   Congruent with the above statement, EDI envelope headers are NOT
   visible in the MIME package.

   In order to optimize routing from existing commercial EDI networks
   (called Value Added Networks or VANs) to the Internet, it would be
   useful to make some envelope information visible.  This
   specification, however, provides no support for this optimization.

   o  X12.58 and UN/EDIFACT security considerations

   The most common EDI standards bodies, ANSI X12 and EDIFACT, have
   defined internal provisions for security.  X12.58 is the security
   mechanism for ANSI X12 and AUTACK provides security for EDIFACT. This
   specification does NOT dictate use or non-use of these security
   standards.  They are both fully compatible, though possibly
   redundant, with this specification.

   2.4.2 Flexibility assumptions

   o  Encrypted or unencrypted data

   This specification allows for EDI/EC message exchange where the
   EDI/EC data can either be unprotected or protected by means of
   encryption.

   o  Signed or unsigned data

   This specification allows for EDI/EC message exchange with or without
   digital signature of the original EDI transmission.

   o  Use of receipt or not

   This specification allows for EDI/EC message transmission with or
   without a request for receipt notification.  If a signed receipt
   notification is requested however, a MIC value is REQUIRED as part
   of the returned receipt, except when a severe error condition
   prevents computation of the digest value. In the exceptional case,
   a signed receipt should be returned with an error message that
   effectively explains why the MIC is absent.

   o  Use of synchronous or asynchronous receipts

   This specification allows in addition to a receipt request the

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   specification of the type of receipt that should be returned. It
   supports synchronous or asynchronous receipts in the MDN format
   specified in section 7 of this document.

   o  Security Formatting

   This specification relies on the guidelines set forth in RFC
   3851/3852  [8] "S/MIME Version 3.1 Message Specification;
   Cryptographic Message Syntax".

   o  Hash function, message digest choices

   When a signature is used, it is RECOMMENDED that the SHA-1 hash
   algorithm be used for all outgoing messages, and that both MD5 and
   SHA-1 be supported for incoming messages.

   o  Permutation Summary

   In summary, the following twelve security permutations are possible
   in any given trading relationship:

      1.   Sender sends un-encrypted data, does NOT request a receipt.
      2.   Sender sends un-encrypted data, requests an unsigned receipt.
           The receiver sends back the unsigned receipt.
      3.   Sender sends un-encrypted data, requests a signed receipt.
           The receiver sends back the signed receipt.
      4.   Sender sends encrypted data, does NOT request a receipt.
      5.   Sender sends encrypted data, requests an unsigned receipt.
           The receiver sends back the unsigned receipt.
      6.   Sender sends encrypted data, requests a signed receipt.
           The receiver sends back the signed receipt.
      7.   Sender sends signed data, does NOT request a signed or
           unsigned receipt.
      8.   Sender sends signed data, requests an unsigned receipt.
           Receiver sends back the unsigned receipt.
      9.   Sender sends signed data, requests a signed receipt.
           Receiver sends back the signed receipt.
      10.  Sender sends encrypted and signed data, does NOT request a
           signed or unsigned receipt.
      11.  Sender sends encrypted and signed data, requests an unsigned
           receipt. Receiver sends back the unsigned receipt.
      12.  Sender sends encrypted and signed data, requests a signed
           receipt. Receiver sends back the signed receipt.

   Users can choose any of the twelve possibilities, but only the
   last example (12), when a signed receipt is requested, offers the
   whole suite of security features described in the "Secure
   transmission loop" above.

   Additionally, the receipts discussed above may be either synchronous
   or asynchronous in nature depending on the type requested. The use of

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   either the synchronous or asynchronous receipts does not change the
   nature of the "Secure transmission loop" in support of NRR.

   3.0 Referenced RFC's and their contribution

   3.1 RFC 2616 HTTP v1.1 [3]

   This document specifies how data is transferred using HTTP.

   3.2 RFC 1847 MIME Security Multiparts [6]

   This document defines security multipart for MIME:
   multipart/encrypted and multipart/signed.

   3.3 RFC 3462 Multipart/report [9]

   This RFC defines the use of the multipart/report content type,
   something that the MDN RFC 3798 builds upon.

   3.4 RFC 1767 EDI Content [2]

   This RFC defines the use of content type "application" for ANSI X12
   (application/EDI-X12), EDIFACT (application/EDIFACT) and mutually
   defined EDI (application/EDI-Consent).

   3.5 RFC 2045, 2046, and 2049 MIME [1]

   These are the basic MIME standards, upon which all MIME related RFCs
   build, including this one.  Key contributions include definition of
   "content type", "sub-type" and "multipart", as well as encoding
   guidelines, which establishes 7-bit US-ASCII as the canonical
   character set to be used in Internet messaging.

   3.6 RFC 3798 Message Disposition Notification [5]

   This Internet RFC defines how a MDN is requested, and the format and
   syntax of the MDN. The MDN is the basis upon which receipts and
   signed receipts are defined in this specification.

   3.7 RFC 3851 and 3852 S/MIME Version 3.1 Message Specifications and
   Cryptographic Message Syntax (CMS) [8]

   This specification describes how S/MIME shall carry CMS Objects.

   3.8 RFC 3023 XML Media Types [12]

   This RFC defines the use of content type "application" for XML
   (application/xml).

   4.0 Structure of an AS2 message


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   4.1 Introduction

   The basic structure of an AS2 messages consists of MIME format inside
   an HTTP message with a few additional specific AS2 headers. The
   structures below are described hierarchically in terms of which RFC's
   are applied to form the specific structure.  For details of how to
   code in compliance with all RFC's involved, turn directly to the
   RFC's referenced. Any difference between AS2 implantations and RFCs
   are mentioned specifically in the sections below.

   4.2 Structure of an Internet EDI MIME message

   No encryption, no signature
      -RFC2616/2045
         -RFC1767/RFC3023 (application/EDIxxxx or /xml)

   No encryption, signature
      -RFC2616/2045
        -RFC1847 (multipart/signed)
          -RFC1767/RFC3023 (application/EDIxxxx or /xml)
          -RFC3851 (application/pkcs7-signature)

   Encryption, no signature
      -RFC2616/2045
        -RFC3851 (application/pkcs7-mime)
          -RFC1767/RFC3023  (application/EDIxxxx or /xml)(encrypted)

   Encryption, signature
      -RFC2616/2045
        -RFC3851 (application/pkcs7-mime)
          -RFC1847 (multipart/signed)(encrypted)
            -RFC1767/RFC3023  (application/EDIxxxx or
             /xml)(encrypted)
            -RFC3851 (application/pkcs7-signature)(encrypted)

   MDN over HTTP, no signature
      -RFC2616/2045
        -RFC3798 (message/disposition-notification)

   MDN over HTTP, signature
      -RFC2616/2045
        -RFC1847 (multipart/signed)
         -RFC3798 (message/disposition-notification)
         -RFC3851 (application/pkcs7-signature)

   MDN over SMTP, no signature
   MDN over SMTP, signature
     Refer to the EDI over SMTP standard [4].

   While all MIME content types SHOULD be supported. The
   following MIME content types MUST be supported:

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             Content-type: multipart/signed
             Content-Type: multipart/report
             Content-type: message/disposition-notification
             Content-Type: application/PKCS7-signature
             Content-Type: application/PKCS7-mime
             Content-Type: application/EDI-X12
             Content-Type: application/EDIFACT
             Content-Type: application/edi-consent
             Content-Type: application/XML

   5.0 HTTP Considerations

   5.1 Sending EDI in HTTP POST Requests

   The request line will have the form: "POST Request-URI HTTP/1.1",
   with spaces and followed by a CRLF. The Request URI is typically
   exchanged out of band, as part of setting up a bilateral trading
   partner agreement. Applications SHOULD be prepared to deal with an
   initial reply containing a status indicating a need for
   authentication of the usual types used for authorizing access to the
   Request-URI ([3], section 10.4.2 and elsewhere).

   The request line is followed by entity headers specifying content
   length ([3] section 14.14) and content type ([3],section 14.18). The
   Host request header ([3] sections 9 and 14.23) is also included.

   When using Transport Layer Security [10] or SSLv3, the request-URI
   SHOULD indicate the appropriate scheme value, HTTPS. Usually only a
   multipart/signed message body would be sent using TLS, as encrypted
   message bodies would be redundant. However, encrypted message bodies
   are not prohibited.

   The receiving AS2 system MAY disconnect from the sending AS2 system
   before completing the reception of the entire entity if it determines
   the entity being sent is too large to process.

   For HTTP version 1.1, TCP persistent connections are the default,
   ([3] sections 8.1.2, 8.2, and 19.7.1). A number of other differences
   exist because HTTP does not conform to MIME [1] as used in SMTP
   transport. Relevant differences are summarized below.

   5.2 Unused MIME Headers and Operations

   5.2.1 Content-Transfer-Encoding not used in HTTP transport

   HTTP can handle binary data and so there is no need to use the
   content transfer encodings of MIME [1]. This difference is discussed
   in [3] section 19.4.5. However, a Content transfer encoding value of
   binary or 8-bit is permissible but not required. The absence of this
   header MUST NOT result in transaction failure. Content transfer

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   encoding of MIME bodyparts within the AS2 message body is also
   allowed.

   5.2.2 Message bodies

   In [3] section 3.7.2, it is explicitly noted that multiparts MUST
   have null epilogues.

   In [4], sections 5.4.1, options for large file processing are
   discussed for SMTP transport. For HTTP, large files SHOULD be handled
   correctly by the TCP layer. However, [3] sections 3.5 and 3.6 discuss
   some options for compressing or chunking entities to be transferred.
   [3] Section 8.1.2.2 discusses a pipelining option that is useful for
   segmenting large amounts of data.

   5.3 Modification of MIME or other headers or parameters used

   5.3.1 Content-Length

   The use of the content-length header MUST follow the guidelines of
   [3], specifically sections 4.4 and 14.13.

   5.3.2 Final Recipient and Original Recipient

   The final and original recipient values SHOULD be the same value.
   These values MUST NOT be aliases or mailing lists.

   5.3.3 Message-Id and Original-Message-Id

   Message-Id and Original-Message-Id is formatted as defined in
   RFC2822:

          "<" id-left "@" id-right ">"        (RFC2822 3.6.4)

   Message-Id length is a maximum of 998 characters. For maximum
   backward compatibility, Message-Id length SHOULD be 255 characters or
   less. Message-Id SHOULD be globally unique, id-right SHOULD be
   something unique to the sending host environment (e.g. a host name).

   When sending a message, always include the angle brackets. Angle
   brackets are not part of the Message-Id value. For maximum backward
   compatibility, when receiving a message, do not check for angle
   brackets. When creating the Original-Message-Id header in an MDN,
   always use the exact syntax as received on the original message;
   don't strip or add angle brackets.

   5.3.4 Host header

   The host request header field MUST be included in the POST request
   made when sending business data. This field is to allow one server IP
   address to service multiple hostnames, and potentially conserve IP

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   addresses. See [3], sections 14.23 and 19.5.1.

   5.4 HTTP Response Status Codes

   The status codes return status concerning HTTP operations. For
   example, the status code 401, together with the WWW- Authenticate
   header, is used to challenge the client to repeat the request with
   an Authorization header. Other explicit status codes are documented
   in [3], sections 6.1.1 and throughout section 10.

   For errors in the request-URI, 400 ("Bad Request"), 404 ("Not Found")
   and similar codes are appropriate status codes. These codes and their
   semantics are specified by [3]. A careful examination of these codes
   and their semantics should be made before implementing any retry
   functionality. Retries SHOULD NOT be made if the error is not
   transient or if retries are explicitly discouraged.

   5.5 HTTP Error Recovery

   If the HTTP client fails to read the HTTP server response data, the
   POST operation with identical content, including same Message-ID
   SHOULD be repeated, if the condition is transient.

   The Message-ID on a POST operation can be reused if and only if all
   of the content (including the original Date) is identical.

   Details of the retry process -- including time intervals to pause,
   number of retries to attempt, timeouts for retrying are
   implementation dependent. These settings are selected as part of the
   trading partner agreement.

   Servers SHOULD be prepared to receive a POST with a repeated
   Message-ID. The MIME reply body previously sent SHOULD be resent,
   including the MDN and other MIME parts.

   6.0 Additional AS2 Specific HTTP Headers

   The following headers are to be included in all AS2 messages and all
   AS2 MDNs, except for asynchronous MDNs that are sent using SMTP and
   follow the AS1 semantics[4].

   6.1  AS2 Version Header

   To promote backward compatibility AS2 includes a version:

   AS2-Version: 1.0  - Used in all implementations implementing this
                       specification. 1.x will be interpreted as 1.0 by
                       all implementation implemented with the AS2
                       Version: 1.0 header. That is only the most
                       significant digit is used as the version
                       identifier for those not implementing additional

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                       non-AS2 specified functionality.
                       AS2-Version: 1.0 through 1.9 MAY be used
                       All implementations MUST interpret "1.0 through
                       1.9" as implementing this specification. However
                       Implementation MAY extend this specification with
                       additional functionality by specifying versions
                       1.1 through 1.9. If this mechanism is used the
                       additional functionality MUST be completely
                       transparent to implementations with AS2-Version:
                       1.0 designation.

   AS2-Version: 1.1  - Designates those implementations which support
                       compression as defined by RFC 3274.

   Receiving systems MUST NOT fail due to the absence of the AS2-Version
   header.  Absence would indicate the message is from an implementation
   based on a previous version of this specification.

   6.2  AS2 System Identifiers

   To aid the receiving system in identifying the sending system,
   AS2-From and AS2-To headers are used.

          AS2-From: < AS2-name >
          AS2-To: < AS2-name >

   These AS2 headers contain textual values, as described below,
   identifying the sender/receiver of a data exchange. Their values may
   be company specific, such as DUNS number, or it may be simply an
   identification string agreed upon between the trading partners.

        AS2-text = "!" /           ; printable ASCII characters
                   %d35-91 /       ; except double-quote (%d34)
                   %d93-126        ; or backslash (%d92)

        AS2-qtext = AS2-text / SP  ; allow space only in quoted text

        AS2-quoted-pair = "\" DQUOTE /  ; \" or
                          "\" "\"       ; \\

        AS2-quoted-name = DQUOTE 1*128( AS2-qtext /
                                        AS2-quoted-pair) DQUOTE

        AS2-atomic-name = 1*128AS2-text

        AS2-name = AS2-atomic-name / AS2-quoted-name

   The AS2-From header value and the AS2-To header value MUST each be an
   AS2-name, MUST each be comprised of from 1 to 128 printable ASCII
   characters and MUST NOT be folded. The value in each of these headers
   is case-sensitive. The string definitions given above are in ABNF

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   format.

   The AS2-quoted-name SHOULD be used only if the AS2-name does not
   conform to AS2-atomic-name.

   The AS2-To and AS2-From header fields MUST be present in all AS2
   messages and AS2 MDN's whether asynchronous or synchronous in nature,
   except for asynchronous MDNs which are sent using SMTP.

   The AS2-name for the AS2-To header in a response or MDN  MUST match
   the AS2-name of the AS2-From header in the corresponding request
   message. Likewise, the AS2-name for the AS2-From header in a response
   or MDN MUST match the AS2-name of the AS2-To header in the
   corresponding AS2 request message.

   The sending system may choose to limit the possible AS2- To/AS2-From
   textual values but MUST not exceed them. The receiving system MUST
   make no restrictions on the textual values and SHOULD handle all
   possible implementations. However, implementers must be aware that
   older AS2 products may not adhere to this convention. Trading partner
   agreements should be made to insure that older products can support
   the system identifiers that are used.

   There is no required response to a client request containing invalid
   or unknown AS2-From or AS2-To header values. The receiving AS2 system
   MAY return an unsigned MDN with an explanation of the error, if the
   sending system requested an MDN.

   7.0 Structure and Processing of an MDN Message

   7.1   Introduction

   In order to support non-repudiation of receipt, a signed receipt,
   based on digitally signing a message disposition notification, is to
   be implemented by a receiving trading partner's UA. The message
   disposition notification, specified by RFC 3798, is digitally signed
   by a receiving trading partner as part of a multipart/signed MIME
   message.

   The following support for signed receipts is REQUIRED:

         1. The ability to create a multipart/report; where the
            report-type = disposition-notification.
         2. The ability to calculate a message integrity check (MIC) on
            the received message. The calculated MIC value will be
            returned to the sender of the message inside the signed
            receipt.
         3. The ability to create a multipart/signed content with the
            message disposition notification as the first body part, and
            the signature as the second body part.
         4. The ability to return the signed receipt to the sending

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            trading partner.
         5. The ability to return either a synchronous or asynchronous
            receipt as the sending party requests.

   The signed receipt is used to notify a sending trading partner that
   requested the signed receipt that:

        1. The receiving trading partner acknowledges receipt of the
           sent EC Interchange.
        2. If the sent message was signed, then the receiving trading
           partner has authenticated the sender of the EC Interchange.
        3. If the sent message was signed, then the receiving trading
           partner has verified the integrity of the sent EC
           Interchange.

   Regardless of whether the EDI/EC Interchange was sent in S/MIME
   format or not, the receiving trading partner's UA MUST provide the
   following basic processing:

        1. If the sent EDI/EC Interchange is encrypted, then the
           encrypted symmetric key and initialization vector (if
           applicable) is decrypted using the receiver's private key.
        2. The decrypted symmetric encryption key is then used to
           decrypt the EDI/EC Interchange.
        3. The receiving trading partner authenticates signatures in a
           message using the sender's public key. The authentication
           algorithm performs the following:
              a. The message integrity check (MIC or Message Digest), is
                 decrypted using the sender's public key.
              b. A MIC on the signed contents (the MIME header and
                 encoded EDI object, as per RFC 1767) in the message
                 received is calculated using the same oneway hash
                 function that the sending trading partner used.
              c. The MIC extracted from the message that was sent, and
                 the MIC calculated using the same oneway hash function
                 that the sending trading partner used is compared for
                 equality.
        4. The receiving trading partner formats the MDN and sets the
           calculated MIC into the "Received-content-MIC" extension
           field.
        5. The receiving trading partner creates a multipart/signed MIME
           message according to RFC 1847.
        6.  The MDN is the first part of the multipart/signed message,
           and the digital signature is created over this MDN, including
           its MIME headers.
        7. The second part of the multipart/signed message contains the
           digital signature. The "protocol" option specified in the
           second part of the multipart/signed is as follows:

               S/MIME: protocol = "application/pkcs-7-signature"


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        8. The signature information is formatted according to S/MIME
           specifications.

   The EC Interchange and the RFC 1767 MIME EDI content header can
   actually be part of a multi-part MIME content-type. When the EDI
   Interchange is part of a multi-part MIME content-type, the MIC MUST
   be calculated across the entire multi-part content, including the
   MIME headers.

   The signed MDN, when received by the sender of the EDI Interchange
   can be used by the sender:

        o  As an acknowledgment that the EDI Interchange sent, was
           delivered and acknowledged by the receiving trading partner.
           The receiver does this by returning the original-message-id
           of the sent message in the MDN portion of the signed receipt.

        o  As an acknowledgment that the integrity of the EDI
           Interchange was verified by the receiving trading partner.
           The receiver does this by returning the calculated MIC of
           the received EC Interchange (and 1767 MIME headers) in the
           "Received-content-MIC" field of the signed MDN.

        o  As an acknowledgment that the receiving trading partner has
           authenticated the sender of the EDI Interchange.

        o  As a non-repudiation of receipt when the signed MDN is
           successfully verified by the sender with the receiving
           trading partner's public key and the returned MIC value
           inside the MDN is the same as the digest of the original
           message.

   7.2 Synchronous and Asynchronous MDNs

   The AS2-MDN exists in two varieties: synchronous and asynchronous.

   The synchronous AS2-MDN is sent as an HTTP response to an HTTP POST
   or as an HTTPS response to an HTTPS POST. This form of AS2-MDN is
   called synchronous because the AS2-MDN is returned to the originator
   of the POST on the same TCP/IP connection.

   The asynchronous AS2-MDN is sent on a separate HTTP, HTTPS, or SMTP
   TCP/IP connection. Logically, the asynchronous AS2- MDN is a response
   to an AS2 message. However, at the transfer-protocol layer, assuming
   that no HTTP pipelining is utilized, the asynchronous AS2-MDN is
   delivered on a unique TCP/IP connection, distinct from that used to
   deliver the original AS2 message. When handling an asynchronous
   request, the HTTP response MUST be sent back before the MDN is
   processed and sent on the separate connection.

   When an asynchronous AS2-MDN is requested by the sender of an AS2

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   message, the synchronous HTTP or HTTPS response returned to the
   sender prior to terminating the connection MUST be a transfer-layer
   response indicating the success or failure of the data transfer. The
   format of such a synchronous response MAY be the same as that
   response returned when no AS2-MDN is requested.

   The following diagram illustrates the synchronous versus asynchronous
   varieties of AS2-MDN delivery using HTTP:

   Synchronous AS2-MDN

   [Peer1] ----( connect )----> [Peer2]
   [Peer1] -----( send )------> [Peer2]   [HTTP Request [AS2-Message]]
   [Peer1] <---( receive )----- [Peer2]   [HTTP Response [AS2-MDN]]

   Asynchronous AS2-MDN

   [Peer1] ----( connect )----> [Peer2]
   [Peer1] -----( send )------> [Peer2]   [HTTP Request [AS2-Message]]
   [Peer1] <---( receive )----- [Peer2]   [HTTP Response]

   [Peer1]*<---( connect )----- [Peer2]
   [Peer1] <--- ( send )------- [Peer2]   [HTTP Request [AS2-MDN]]
   [Peer1] ----( receive )----> [Peer2]   [HTTP Response]

   * Note: An AS2-MDN may be directed to a different host than that of
   the sender of the AS2 message. It may utilize a different transfer
   protocol than that used to send the original AS2 message.

   The advantage of the synchronous MDN is that it can provide the
   sender of the AS2 Message with a verifiable confirmation of message
   delivery within a synchronous logic flow. However, if the message is
   relatively large, the time required to process this message and
   return an AS2-MDN to the sender on the same TCP/IP connection may
   exceed the maximum configured time permitted for an IP connection.

   The advantage of the asynchronous MDN is that it provides for the
   rapid return of a transfer-layer response from the receiver
   confirming the receipt of data, therefore not requiring a TCP/IP
   connection to necessarily remain open for very long. However, this
   design requires that the asynchronous AS2-MDN contain enough
   information to uniquely identify the original message so that, when
   received by the AS2 Message originator, the status of the original
   AS2 Message can be properly updated based on the contents of the
   AS2-MDN.

   Synchronous or asynchronous HTTP or HTTPS MDNs are handled according
   to the requirements of this specification.

   However, SMTP MDNs are formatted according to the requirements of
   RFC 3335 [4].

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   7.3 Requesting a Signed Receipt

   Message Disposition Notifications are requested as per RFC 3798.  A
   request that the receiving user agent issue a message disposition
   notification is made by placing the following header into the message
   to be sent:

        MDN-request-header = "Disposition-notification-to"
                            ":"  mail-address

   Example requesting a MDN:

        Disposition-notification-to: xxx@example.com

   This syntax is a residue of the use of MDNs using SMTP transfer.
   Since this specification is adjusting the functionality from SMTP to
   HTTP while retaining as much as possible from the [4] functionality,
   the mail-address MUST be present. The mail-address field is
   specified as an RFC 2822 localpart@domain [addr-spec] address.
   However, the address is not used to identify where to return
   the MDN. Receiving applications MUST ignore the value, and not
   complain about RFC 2822 address syntax violations.

   When requesting MDN based receipts, the originator supplies
   additional extension headers that precede the message body.
   These header "tags" are as follows:

   A Message-ID header is added to support message reconciliation,
   so that an Original-Message-Id value can be returned in the body
   part of MDN. Other headers, especially "Subject" and "Date", SHOULD
   be supplied; the values of these headers are often mentioned in
   the human-readable section of a MDN to aid in identifying the
   original message.

   MDNs will be returned in the HTTP response when requested unless
   an asynchronous return is requested.

   To request an asynchronous message disposition notification, the
   following header is placed into the message that is sent:

        Receipt-Delivery-Option: return-URL

   Here is an example requesting the MDN to be asynchronous

        Receipt-Delivery-Option: http://www.example.com/Path

   Receipt-delivery-option syntax allows return-url to use some schemes
   other that HTTP using the POST method.

   The "receipt-delivery-option: return-url" string indicates the URL

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   to use for an asynchronous MDN. This header is NOT present if the
   receipt is to be synchronous. The email value in
   Disposition-notification-to is not used in this specification
   because it was limited to RFC 2822 addresses; the extension header
   "Receipt-delivery-option" has introduced to provide a URL for
   the MDN return by several transfer options.

   The receipt-delivery-option's value MUST be a URL indicating the
   delivery transport destination for the receipt.

   An example request for an asynchronous MDN via an HTTP transport:

        Receipt-delivery-option: http://www.example.com

   An example request for an asynchronous MDN via an HTTP/S transport:

        Receipt-delivery-option: https://www.example.com

   An example request for an asynchronous MDN via an SMTP transport:

        Receipt-delivery-option: mailto:as2@example.com

   For more information on requesting SMTP MDNs, refer to RFC 3335 [4].

   Finally, the header, Disposition-notification-options, identifies
   characteristics of message disposition notification as in [5].
   The most important of these options is for indicating the signing
   options for the MDN as in the following example:

        Disposition-notification-options:
             signed-receipt-protocol=optional,pkcs7-signature;
             signed-receipt-micalg=optional,sha1,md5

   For signing options, consider the disposition-notification-options
   syntax:

        Disposition-notification-options =
                 "Disposition-Notification-Options" ":"
                  disposition-notification-parameters

    where
             disposition-notification-parameters =
                               parameter *(";" parameter)

    where
             parameter = attribute "=" importance ", " 1#value"

    where
             importance = "required" | "optional"

   So the Disposition-notification-options string could be:

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        signed-receipt-protocol=optional,<protocol symbol>;
        signed-receipt-micalg=optional,<micalg1>,<micalg2>,...;

   The currently used value for <protocol symbol> is "pkcs7-signature"
   for the S/MIME detached signature format.

   The currently supported values for MIC algorithm <micalg> values are:

        Algorithm   Value Used
        ---------    -------
         SHA-1        sha1
         MD5          md5

   The semantics of the "signed-receipt-protocol" and the
   "signed-receipt-micalg" parameters are as follows:

   1. The "signed-receipt-protocol" parameter is used to request a
   signed receipt from the recipient trading partner. The
   "signed-receipt-protocol" parameter also specifies the format
   in which the signed receipt SHOULD be returned to the requester.

   The "signed-receipt-micalg" parameter is a list of MIC algorithms
   preferred by the requester for use in signing the returned receipt.
   The list of MIC algorithms SHOULD be honored by the recipient from
   left to right.

   Both the "signed-receipt-protocol" and the "signed- receipt-micalg"
   option parameters are REQUIRED when requesting a signed receipt.

   The lack of the presence of the "Receipt-Delivery-Option" indicates a
   receipt is synchronous in nature. The presence of the
   "Receipt-Delivery-Option: return-url" indicates that an asynchronous
   receipt is requested and SHOULD be sent to the "return-url".

   2. The "importance" attribute of "Optional" is defined in the RFC
   3798 section 2.2 and has the following meaning:

   Parameters with an importance of "Optional" permit a UA that does not
   understand the particular options parameter to still generate a MDN
   in response to a request for a MDN.

   A UA that does not understand the "signed-receipt-protocol"
   parameter, or the "signed-receipt-micalg" will obviously not return a
   signed receipt.

   The importance of "Optional" is used for the signed receipt
   parameters because it is RECOMMENDED that an MDN be returned to the
   requesting trading partner even if the recipient could not sign it.


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   The returned MDN will contain information on the disposition of the
   message as well as why the MDN could not be signed. See the
   Disposition field in section 7.5 for more information.

   Within an EDI trading relationship, if a signed receipt is expected
   and is not returned, then the validity of the transaction is up to
   the trading partners to resolve.

   In general, if a signed receipt is required in the trading
   relationship and is not received, the transaction will likely not be
   considered valid.

   7.3.1 Signed receipt considerations

   The method used to request a receipt or a signed receipt is defined
   in RFC 3798, "An Extensible Message Format for Message Disposition
   Notifications".

   The "rule" is:

   1. When a receipt is requested, explicitly specifying that the
   receipt be signed, then the receipt MUST be returned with a
   signature.

   2. When a receipt is requested, explicitly specifying that the
   receipt be signed, but the recipient cannot support either the
   requested protocol format, or requested MIC algorithms, then either a
   signed or unsigned receipt SHOULD be returned.

   3. When a signature is not explicitly requested, or if the signed
   receipt request parameter is not recognized by the UA, then no
   receipt, an unsigned receipt, or a signed receipt MAY be returned by
   the recipient.

   NOTE: For Internet EDI, it is RECOMMENDED that when a signature is
   not explicitly requested, or if parameters are not recognized, that
   the UA send back at a minimum, an unsigned receipt. If a signed
   receipt however was always returned as a policy, whether requested or
   not, then any false unsigned receipts can be repudiated.

   When a request for a signed receipt is made, but there is an error in
   processing the contents of the message, a signed receipt MUST still
   be returned. The request for a signed receipt SHALL still be honored,
   though the transaction itself may not be valid. The reason for why
   the contents could not be processed MUST be set in the
   "disposition-field".

   When a signed receipt request is made, the "Received-content-MIC"
   MUST always be returned to the requester (except when corruption
   prevents computation of the digest in accordance with the following

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   specification). The "Received-content-MIC" MUST be calculated
   as follows:

      o  For any signed messages, the MIC to be returned is calculated
         on the RFC1767/RFC3023 MIME header and content.
         Canonicalization on the MIME headers MUST be performed
         before the MIC is calculated, since the sender requesting
         the signed receipt was also REQUIRED to canonicalize.

      o  For encrypted, unsigned messages, the MIC to be returned is
         calculated on the decrypted RFC 1767/RFC3023 MIME header
         and content. The content after decryption MUST be canonicalized
         before the MIC is calculated.

     o  For unsigned, unencrypted messages, the MIC MUST be calculated
         over the message contents without the MIME or any other RFC
         822 headers, since these are sometimes altered or reordered
         by MTAs.

   7.4 MDN Format and Values

   This section defines the format of the AS2 Message Disposition
   Notification (AS2-MDN).

   7.4.1 AS2-MDN general formats

   The AS2-MDN follows the MDN specification [5] except where noted in
   this section. The modified ABNF definitions in this document use
   the vertical-bar character, '|', to denote a logical "OR"
   construction. This usage follows RFC 2616 [3]. HTTP entities referred
   to below are not further defined in this document. Refer to RFC 2616
   [3] for complete definitions of HTTP entities. The format of the
   AS2-MDN is:

   AS2-MDN = AS2-sync-MDN | AS2-async-http-MDN |
       AS2-async-smtp-MDN

   AS2-sync-MDN =
       Status-Line
       *(( general-header | response-header | entity-header )
       CRLF )
       CRLF
       AS2-MDN-body

   Status-Line =
       HTTP-Version SP Status-Code SP Reason-Phrase CRLF

   AS2-async-http-MDN =
       Request-Line
       *(( general-header | request-header | entity-header )
       CRLF )

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       CRLF
       AS2-MDN-body

   Request-Line =
       Method SP Request-URI SP HTTP-Version CRLF

   AS2-async-smtp-MDN =
       *(( general-header | request-header | entity-header )
       CRLF )
       CRLF
       AS2-MDN-body

   AS2-MDN-body =
       AS2-signed-MDN-body | AS2-unsigned-MDN-body

   7.4.2 AS2-MDN construction

   The AS2-MDN-body is formatted as a MIME multipart/report with a
   report-type of "disposition-notification". When unsigned, the
   transfer-layer ( "outermost" ) entity-headers of the AS2-MDN contain
   the content-type header that specifies a content-type of
   "multipart/report" and parameters indicating the report-type, and the
   value of the outermost multipart boundary.

   When the AS2-MDN is signed, the transfer-layer ("outermost")
   entity-headers of the AS2-MDN contain a content-type header that
   specifies a content-type of "multipart/signed" and parameters
   indicating the algorithm used to compute the message digest, the
   signature formatting protocol ( e.g.pkcs7-signature ), and the value
   of the outermost multipart boundary. The first part of the MIME
   multipart/signed message is an embedded MIME multipart/report of type
   "disposition-notification". The second part of the multipart/signed
   message contains a MIME application/pkcs7-signature message.

   The first part of the MIME multipart/report is a "human-readable"
   portion that contains a general description of the message
   disposition. The second part of the MIME multipart/report is a
   "machine-readable" portion that is defined as:

   AS2-disposition-notification-content =
       [ reporting-ua-field CRLF ]
       [ mdn-gateway-field CRLF ]
       final-recipient-field CRLF
       [ original-message-id-field CRLF ]
       AS2-disposition-field CRLF
       *( failure-field CRLF )
       *( error-field CRLF )
       *( warning-field CRLF )
       *( extension-field CRLF )
       [ AS2-received-content-MIC-field CRLF ]


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   7.4.3 AS2-MDN fields

   The rules for constructing the AS2-disposition-notification content
   are identical to those for the disposition-notification-content
   rules provided in section 7 of RFC 3798 [5] except that
   the RFC 3798 disposition-field has been replaced with the
   AS2-disposition-field and that the AS2-received-content-MIC field has
   been added. The differences between the RFC 3798 disposition-field
   and the AS2-disposition-field are described below. Where there are
   differences between this document and RFC 3798, those entity names
   have been changed by pre-pending "AS2-". Entities that do not
   differ from RFC 3798 are not necessarily further defined in this
   document; refer to RFC 3798, section 7 "Collected Grammar"
   for the original grammar.

   AS2-disposition-field =
       "Disposition" ":" disposition-mode ";"
       AS2-disposition-type [ '/' AS2-disposition-modifier ]

   disposition-mode =
       action-mode "/" sending-mode

   action-mode =
       "manual-action" | "automatic-action"

   sending-mode =
       "MDN-sent-manually" | "MDN-sent-automatically"

   AS2-disposition-type =
       "processed" | "failed"

   AS2-disposition-modifier =
       ( "error" | "warning" ) | AS2-disposition-modifier-extension

   AS2-disposition-modifier-extension =
       "error: authentication-failed" |
       "error: decompression-failed" |
       "error: decryption-failed" |
       "error: insufficient-message-security" |
       "error: integrity-check-failed" |
       "error: unexpected-processing-error" |
       "warning: " AS2-MDN-warning-description |
       "failure: " AS2-MDN-failure-description

   AS2-MDN-warning-description = *( TEXT )

   AS2-MDN-failure-description = *( TEXT )

   AS2-received-content-MIC-field =
       "Received-content-MIC" ":" encoded-message-digest ","
       digest-alg-id CRLF

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   encoded-message-digest =
       1*( 'A'-Z' | 'a'-'z' | '0'-'9' | '/' | '+' | '=' )  (
       i.e. base64( message-digest ) )

   digest-alg-id = "sha1" | "md5"

   "Insufficient-message-security" and "decompression-failed" are new
   error codes that are not mentioned in the AS1 RFC 3335,
   and may not be compatible with earlier implementations of AS2.

   The "Received-content-MIC" extension field is set when the integrity
   of the received message is verified. The MIC is the base64-encoded
   message-digest computed over the received message with a hash
   function. This field is required for signed receipts but optional for
   unsigned receipts. For details defining the specific content over
   which the message digest is to be computed, see Section 7.3.1 of
   this document.

   For signed messages, the algorithm used to calculate the MIC MUST be
   the same as the algorithm that was used on the message that was
   signed. If the message is not signed, then the SHA-1 algorithm SHOULD
   be used. This field is set only when the contents of the message are
   processed successfully. This field is used in conjunction with the
   recipient's signature on the MDN in order for the sender to verify
   non-repudiation of receipt.

   AS2-MDN field names ( e.g. "Disposition:", "Final-Recipient:")
   are case-insensitive ( cf. RFC 3798, 3.1.1 ).  AS2-MDN action-modes,
   sending-modes, AS2-disposition-types, and AS2-disposition-modifier
   values that are defined above, and user-supplied *( TEXT ) values
   are also case insensitive. AS2 implementations MUST NOT make
   assumptions regarding the values supplied for AS2-MDN-
   warning-description, AS2-MDN-failure-description nor for the values
   of any (optional) error, warning, or failure fields.

   7.4.4 Additional AS2-MDN programming notes

      o  Unlike SMTP, for HTTP transactions, Original-Recipient and
         Final-Recipient SHOULD not be different. The value in
         Original-Message-ID SHOULD match the original Message-ID
         header value.

      o  Refer to RFC 3798 for the formatting of the MDN except for the
         specific deviations mentioned above.

      o  Refer to RFC 3462 and RFC 3798 for the formatting of the
         content-type entity-headers for the MDN.


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      o  Use an action-mode of "automatic-action" when the disposition
         described by the disposition type was a result of an automatic
         action, rather than an explicit instruction by the user for
         this message.

      o  Use an action-mode of "manual-action" when the disposition
         described by the disposition type was a result of an explicit
         instruction by the user rather than some sort of automatically
         performed action.

      o  Use a sending-mode of "MDN-sent-automatically" when the MDN is
         sent because the UA had previously been configured to do so.

      o  Use a sending-mode of "MDN-sent-manually" when the user
         explicitly gave permission for this particular MDN to be sent.

      o  The sending-mode "MDN-sent-manually" is ONLY meaningful with
         "manual-action", not with "automatic-action".

      o  The "failed" disposition type MUST NOT be used for the
         situation in which there is some problem in processing the
         message other than interpreting the request for an MDN. The
         "processed" or other disposition type with appropriate
         disposition modifiers is to be used in such situations.

   7.5 Disposition Mode, Type, and Modifier

   7.5.1 Disposition mode overview

   This section would provide a brief overview of how processed, error,
   failure, and warnings are used.

   7.5.2 Successful processing status indication

   When the request for a receipt or signed receipt, and the received
   message contents are successfully processed by the receiving EDI UA,
   a receipt or MDN SHOULD be returned with the disposition-type set
   to 'processed'. When the MDN is sent automatically by the EDI UA, and
   there is no explicit way for a user to control the sending of the
   MDN, then the first part of the "disposition-mode" SHOULD be set to
   "automatic-action". When the MDN is being sent under user
   configurable control, then the first part of the "disposition-mode"
   SHOULD be set to "manual-action". Since a request for a signed
   receipt should always be honored, the user MUST not be allowed to
   configure the UA to not send a signed receipt when the sender
   requests one.

   The second part of the disposition-mode is set to "MDN-sent-manually"
   if the user gave explicit permission for the MDN to be
   sent. Again, the user MUST not be allowed to explicitly refuse to
   send a signed receipt when the sender requests one. The second part

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   of the "disposition-mode" is set to "MDN-sent-automatically" whenever
   the EDI UA sends the MDN automatically, regardless of whether the
   sending was under the control of a user, administrator, or software.

   Since EDI content is generally handled automatically by the EDI UA, a
   request for a receipt or signed receipt will generally return the
   following in the "disposition-field":

         Disposition: automatic-action/MDN-sent-automatically; processed

   Note this specification does not restrict the use of the
   "disposition-mode" to just automatic actions. Manual actions are
   valid as long as it is kept in mind that a request for a signed
   receipt MUST be honored.

   7.5.3 Unsuccessful processed content

   The request for a signed receipt requires the use of two
   "disposition-notification-options", which specify the protocol format
   of the returned signed receipt, and the MIC algorithm used to
   calculate the MIC over the message contents. The "disposition-field"
   values that should be used in the case where the message content is
   being rejected or ignored, for instance if the EDI UA determines that
   a signed receipt cannot be returned because it does not support the
   requested protocol format, so the EDI UA chooses not to process the
   message contents itself, MUST be specified in the MDN
   "disposition-field" as follows:

       Disposition: "disposition-mode";  failed/Failure:
        unsupported format

   The "failed" AS2-disposition-type MUST be used when a failure occurs
   that prevents the proper generation of an MDN. For example, this
   disposition-type would apply if the sender of the message requested
   the application of an unsupported message-integrity-check (MIC)
   algorithm.

   The "failure:" AS2-disposition-modifier-extension SHOULD be used with
   an implementation-defined description of the failure. Further
   information about the failure may be contained in a failure-field.

   The syntax of the "failed" disposition-type is general, allowing
   the sending of any textual information along with the "failed"
   disposition-type. Implementations MUST support any printable
   textual characters after the Failure disposition-type.  For use in
   Internet EDI, the following "failed" values are pre-defined and MUST
   be supported:

       "Failure: unsupported format"

       "Failure: unsupported MIC-algorithms"

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   7.5.4 Unsuccessful non-content processing

   When errors occur processing the received message other than content,
   the "disposition-field" MUST be set to the "processed" value of
   disposition-type and the "error" value for disposition-modifier.

   The "error" AS2-disposition-modifier with the "processed"
   disposition-type MUST be used to indicate that an error of some sort
   occurred that prevented successful processing of the message. Further
   information may be contained in an error-field.

   An "error:" AS2-disposition-modifier-extension SHOULD be used to
   combine the indication of an error with a predefined description of a
   specific, well-known error. Further information about the error may
   be contained in an error field.

   For internet EDI use, the following "error" AS2-disposition-modifier
   values are defined:

   o "Error: decryption-failed"           -  the receiver could
                                             not decrypt the
                                             message contents.

   o "Error: authentication-failed"       - the receiver could not
                                            authenticate the sender.

   o "Error: integrity-check-failed"      - the receiver could not
                                            verify content integrity.

   o "Error: unexpected-processing-error" - a catch-all for any
                                            additional processing
                                            errors.

   An example of how the "disposition-field" would look when other than
   content processing errors are detected is as follows:

   Example

       Disposition: "disposition-mode"; processed/Error:
         decryption-failed

   7.5.5 Processing warnings

   Situations arise in EDI where even if a trading partner cannot be
   authenticated correctly, the trading partners still agree to continue
   processing the EDI transactions. Transaction reconciliation is done
   between the trading partners at a later time. In the content
   processing warning situations as described above, the
   "disposition-field' MUST be set to the "processed" disposition-type
   value, and the "warning" "disposition-modifier" value.

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   The "warning" AS2-disposition-modifier MUST be used with the
   "processed" disposition-type to indicate that the message was
   successfully processed but that an exceptional condition occurred.
   Further information may be contained in a warning-field.

   A "warning:" AS2-disposition-modifier-extension SHOULD be used to
   combine the indication of a warning with an implementation-defined
   description of the warning. Further information about the warning may
   be contained in an warning-field.

   For use in Internet EDI, the following "warning"
   disposition-modifier-extension value is defined:

       "Warning: authentication-failed, processing continued"

   An example of how the "disposition-field" would look when other than
   content processing warnings are detected is as follows:

   Example:

       Disposition: "disposition-mode"; processed/Warning:
         authentication-failed, processing continued

   7.5.6 Backwards compatibility with disposition type, modifier and
         extension

   The following set of examples represent typical constructions of the
   Disposition field that have been in use by AS2 implementations. This
   is NOT an exhaustive list of possible constructions. However, AS2
   implementations MUST accept constructions of this type to be backward
   compatible with earlier AS2 versions.

      Disposition: automatic-action/MDN-sent-automatically; processed

      Disposition: automatic-action/MDN-sent-automatically;
       processed/error: authentication-failed

      Disposition: automatic-action/MDN-sent-automatically;
       processed/warning: duplicate-document

      Disposition: automatic-action/MDN-sent-automatically;
       failed/failure: sender-equals-receiver

   The following set of examples represent allowable constructions of
   the Disposition field that combine the historic constructions above
   with optional RFC 3798 error, warning and failure fields. AS2
   implementations MAY produce these constructions. However, AS2 servers
   are not required to recognize or process optional error, warning, or
   failure fields at this time. Note that the use of the multiple Error
   fields in the second example below provides for the indication of

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   multiple error conditions.

      Disposition: automatic-action/MDN-sent-automatically; processed

      Disposition: automatic-action/MDN-sent-automatically;
       processed/error: decryption-failed
      Error: The signature did not decrypt into a valid PKCS#1
       Type-2 block.
      Error: The length of the decrypted key does not equal the
        octet length of the modulus.

      Disposition: automatic-action/MDN-sent-automatically;
        processed/warning: duplicate-document
      Warning: An identical message already exists at the
        destination server.

      Disposition: automatic-action/MDN-sent-automatically;
        failed/failure: sender-equals-receiver
      Failure: The AS2-To name is identical to the AS2-From name.

   The following set of examples represent allowable constructions of
   the Disposition field but that employ pure RFC 3798
   Disposition-modifiers with optional error, warning and failure
   fields. These examples are provided as informational only. These
   constructions are not guaranteed to be backward compatible with
   AS2 implementations prior to version 1.1.

      Disposition: automatic-action/MDN-sent-automatically; processed

      Disposition: automatic-action/MDN-sent-automatically;
       processed/error
      Error: authentication-failed
      Error: The signature did not decrypt into a valid PKCS#1 Type-2
       block.
      Error: The length of the decrypted key does not equal the
       octet length of the modulus.

      Disposition: automatic-action/MDN-sent-automatically;
        processed/warning
      Warning: duplicate-document

      Disposition: automatic-action/MDN-sent-automatically; failed
      Failure: sender-equals-receiver

   7.6  Receipt Reply Considerations in a HTTP POST

   The details of the response to the POST command vary depending upon
   whether a receipt has been requested.

   With no extended header requesting a receipt, and no errors accessing
   the request-URI specified processing, the status line in the Response

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   to the POST request SHOULD be in the 200 range. Status codes in the
   200 range SHOULD also be used when an entity is returned (a signed
   receipt in a multipart/signed content type or an unsigned receipt in
   a multipart/report). Even when the disposition of the data was an
   error condition at the authentication, decryption or other higher
   level, the HTTP status code SHOULD indicate success at the HTTP
   level.

   The HTTP server-side application may respond with an unsolicited
   multipart/report as a message body that the HTTP client might not
   have solicited, but this may be discarded by the client. Applications
   SHOULD avoid emitting unsolicited receipt replies because bandwidth
   or processing limitations might have led administrators to suspend
   asking for acknowledgements.

   Message Disposition Notifications, when used in the HTTP reply
   context, will closely parallel a SMTP MDN. For example, the
   disposition field is a required element in the machine readable
   second part of a multipart/report for a MDN. The
   final-recipient-field ([5] section 3.1) value SHOULD be derived
   from the entity headers of the request.

   In a MDN, the first part of the multipart/report (the
   "human-readable" part) SHOULD include items such as the subject,
   date and other information when those fields are present in entity
   header fields following the POST request.  An application MUST report
   the Message-ID of the request in the second part of the
   multipart/report (the "machine-readable" part). Also, a MDN SHOULD
   have its own unique Message-ID HTTP header. The HTTP reply SHOULD
   normally omit the third optional part of the multipart/report (used
   to return the original message or its headers in the SMTP context).

   8.0 Public Key Certificate Handling

   In the near term, the exchange of public keys and certification of
   these keys MUST be handled as part of the process of establishing a
   trading partnership. The UA and/or EDI application interface must
   maintain a database of public keys used for encryption or signatures,
   in addition to the mapping between EDI  trading partner ID and RFC
   822 [11] email address and http URL/URI. The procedures for
   establishing a trading partnership and configuring the secure EDI
   messaging system might vary among trading partners and software
   packages.

   X.509 certificates are REQUIRED. It is RECOMMENDED that trading
   partners self-certify each other if an agreed upon certification
   authority is not used. This applicability statement does NOT require
   the use of a certification authority. The use of a certification
   authority is therefore OPTIONAL. Certificates may be self-signed.

   It is RECOMMENDED that when trading partners are using S/MIME, that

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   they also exchange public key certificates considering advice
   provided in [15].

   The message formats useful for certificate exchange are found in
   [8] and [16].

   In the long term, additional standards may be developed
   to simplify the process of establishing a trading partnership,
   including the third party authentication of trading partners,
   as well as attributes of the trading relationship.

   9.0 Security Considerations

   This entire document is concerned with secure transport of business
   to business data, and considers both data confidentiality and
   authentication issues.

   Extracted from RFC 3851 [8]:
   40-bit encryption is considered weak by most cryptographers.
   Using weak cryptography in S/MIME offers little actual security over
   sending plaintext.  However, other features of S/MIME, such as the
   specification of tripleDES and the ability to announce stronger
   cryptographic capabilities to parties with whom you communicate,
   allow senders to create messages that use strong encryption.  Using
   weak cryptography is never recommended unless the only alternative is
   no cryptography.  When feasible, sending and receiving agents SHOULD
   inform senders and recipients of the relative cryptographic strength
   of messages.

   Extracted from RFC 3850 [15]:
   When processing certificates, there are many situations where the
   processing might fail. Because the processing may be done by a user
   agent, a security gateway, or other program, there is no single way
   to handle such failures. Just because the methods to handle the
   failures have not been listed, however, the reader should not assume
   that they are not important. The opposite is true: if a certificate
   is not provably valid and associated with the message, the processing
   software should take immediate and noticeable steps to inform the end
   user about it.

   Some of the many places where signature and certificate checking
   might fail include:

      o  no certificate chain leads to a trusted CA
      o  no ability to check the CRL for a certificate
      o  an invalid CRL was received
      o  the CRL being checked is expired
      o  the certificate is expired
      o  the certificate has been revoked

   There are certainly other instances where a certificate may be

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   invalid, and it is the responsibility of the processing software to
   check them all thoroughly, and to decide what to do if the check
   fails. See RFC 3280 for additional information on certificate path
   validation.

   The following are additional security considerations to those listed
   in [8] and [15].

   NRR Cautions

   This specification seeks to provide multiple mechanisms that can be
   combined in accordance with local policies to achieve a wide range
   of security needs as determined by threat and risk analyses of the
   business peers. It is required that all these mechanisms be
   implemented by AS2 software so that the software has capabilities
   that promote strong interoperability, no matter what policies are
   adopted.

   One strong cluster of mechanisms (the secure transmission loop)
   can provide good support for meeting the evidentiary needs
   of non-repudiation of receipt by the original sender and by
   a third party supplied with all stated evidence. However, this
   specification does not itself define non-repudiation of receipt
   nor enumerate its essential properties because NRR is a business
   analyst and/or legal requirement, and not relevantly defined
   by a technical applicability statement.

   Some analyses observe that non-repudiation of receipt presupposes
   that non-repudiation of the sender of the original message obtains,
   and further that non-repudiation should be implemented by means
   of digital signature on the original message. To satisfy strict
   NRR evidence, authentication and integrity MUST be provided by
   some mechanism, and the RECOMMENDED mechanism is to digitally
   sign both the original message and the receipt message.

   Given that this specification has selected several mechanisms that
   can be combined in several ways, it is important to realize that
   if a digital signature is omitted from the original message, in
   order to satisfy the preceding analysis of NRR requirements, some
   authentication mechanism MUST accompany the request for a signed
   receipt and its included Received-content-MIC value. This
   authentication might be from using client-side SSL,
   authentication via IPSEC, or use of HTTP authentication
   (while using SSL). In any case, records of the message content,
   its security basis, and the digest value need to be retained
   for the NRR process.

   So, if NRR is one of the goals of the policy that is adopted,
   by using the mechanisms of the secure transmission
   loop mentioned above and by retaining appropriate records of
   authentication at the original message sender site, strong

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   evidentiary requirements proposed for NRR can be fulfilled.

   Other ways of proceeding may fall short of fulfilling the
   most stringent sets of evidence required for NRR to obtain,
   but may nevertheless have been agreed to as part of a
   commercial trading agreement and, as such, are good enough
   for the parties involved. However, if MDNs are returned
   unsigned, evidentiary requirements for NRR are weak; some
   authentication of the identity of the receiver is needed.

   HTTPS Remark

   The following certificate types MUST be supported for SSL
   server-side certificates.

      o  with URL in the Distinguished Name Common Name attribute
      o  without URL in the Distinguished Name Common Name attribute
      o  self-signed (self-issued)
      o  certification authority certified

   The URL, which matches the source server identity, SHOULD be carried
   in the certificate. However, it is not required to make DNS checks
   or reverse lookups to vouch for the accuracy of the URL or server
   value.  Since server side certificates are to be exchanged and also
   trust established during the configuration of the trading partner
   relationship, runtime checks are not required by implementations
   of this specification.

   The complete certification chain MUST be included in all
   certificates. All certificate verifications MUST "chain to root" or
   to an accepted trust anchor. Additionally, the certificate hash
   SHOULD match the hash recomputed by the receiver.

   Replay Remark

   Because business data documents normally contain transaction ids,
   replays, like resends of not-yet-acknowledged messages, are discarded
   as part of the normal process of duplicate detection. Detection of
   duplicates by Message-Id or by business transaction identifiers is
   recommended.

   10.0 IANA Considerations

   RFC 3335 registered two Disposition-Notification-Options parameters

      Parameter-name: signed-receipt-protocol
      Parameter-name: signed-receipt-micalg

   that are also used by this specification (see section 7.3).

   RFC 3335 also registered on MDN Extension field name

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      Extension field name: Received-content-MIC

   that is also used by this specification (see section 7.4.3).
   Registration of the above is therefore NOT needed.

   10.1 This specification defines an extension to the Message
   Disposition Notification (MDN) protocol for a disposition-modifier
    in the Disposition field of a body of content-type
   "message/disposition-notification".

   10.1.1 Disposition modifier 'warning'

      Parameter-name:  warning
      Semantics: (see sections 7.4.3 and 7.5.5 of this document)

   11.0 Acknowledgements

   Carl Hage, Karen Rosenfeld, Chuck Fenton and many others have
   provided valuable suggestions improving this applicability statement.
   The authors would also like to thank the vendors who participated in
   the Drummond Group Inc. AS2 interoperability testing. Their
   contributions led to great improvement in the clarity of this
   document.

   12.0 References

   12.1 Normative References

   [1]  N. Borenstein,  N.Freed, "Multipurpose Internet Mail Extensions
        (MIME)
           Part One: Format of Internet Message Bodies", RFC 2045,
           December 02, 1996.

           N. Borenstein, N.Freed, "Multipurpose Internet Mail
           Extensions (MIME)
           Part Two: Media Types", RFC 2046, December 02, 1996.

           N. Borenstein, N.Freed, "Multipurpose Internet Mail
           Extensions (MIME)
           Part Five: Conformance Criteria and Examples", RFC 2049,
           December 02, 1996.

   [2]  D. Crocker, "MIME Encapsulation of EDI Objects",  RFC 1767,
           March 2, 1995.

   [3] R. Fielding, J.Gettys, J. Mogul, H. Frystyk, T. Berners- Lee,
       "Hypertext Transfer Protocol--HTTP/1.1", RFC 2616, March 1997.

   [4] T. Harding, R. Drummond, C. Shih, "Peer-to-Peer MIME-based
          Secure Business Data Interchange", RFC 3335, September 2002.

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   [5]  T. Hansen, G. Vaudreuil, "Message Disposition Notification", RFC
   3798, May 2004.

   [6]  J. Galvin, S. Murphy, S. Crocker, N. Freed,  "Security
   Multiparts for MIME: Multipart/Signed and Multipart/Encrypted", RFC
   1847, Oct. 3, 1995

   [8]  B. Ramsdell "S/MIME Version 3.1 Message Specification, RFC 3851,
   July 2004.

   [9]  G. Vaudreuil, "The Multipart/Report Content Type for the
   Reporting of Mail System Administrative Messages", RFC 3462, January,
   2003.

   [11] D. Crocker, "Standard for the Format of ARPA Internet Text
   Messages", STD 11,  RFC 822,  August 13, 1982.

   [12] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types", RFC 3023,
   January 2001.

   [13] Bradner, S., "Key words for use in RFCs to Indicate Requirement
   Levels", BCP 14, RFC 2119, March 1997.

   [14] Bradner, S., "The Internet Standards Process -- Revision 3",
   RFC 2026, October 1996.

   [15] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions
   (S/MIME) Version 3.1 Certificate Handling", RFC 3850, July, 2004.

   [16] R. Housley "Cryptographic Message Syntax CMS", RFC 3852,
   July 2004.

   12.2 Informative References

   [7]  J. Postel, "Simple Mail Transfer Protocol",  STD 10, RFC  821,
   August 1, 1982.

   [10] T. Dierks,C. Allen, "The TLS Protocol Version 1.0" RFC 2246,
   March 1999.

   [17] D. Crocker, "Augmented BNF for Syntax Specifications: ABNF", RFC
   2234, November, 1997.

   13.0  Authors' Addresses

       Dale Moberg
       dmoberg@cyclonecommerce.com
       Cyclone Commerce
       8388 E. Hartford Drive, Suite 100

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       Scottsdale, AZ  85255 USA

       Rik Drummond
       rvd2@drummondgroup.com
       Drummond Group Inc.
       4700 Bryant Irvin Court, Suite 303
       Fort Worth, TX  76107 USA

   Copyright Notice

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

   Appendices

   A. Message Examples

   NOTE: All examples are provided as an illustration only, and are not
   considered part of the protocol specification. If an example
   conflicts with the protocol definitions specified above or in the
   other referenced RFC's, the example is wrong.

   A.1 Signed message requesting a signed, synchronous receipt

   POST /receive HTTP/1.0
   Host: 10.234.160.12:80
   User-Agent: AS2 Company Server
   Date: Wed, 31 Jul 2002 13:34:50 GMT
   From: mrAS2@example.com
   AS2-Version: 1.1
   AS2-From: "\"  as2Name  \""
   AS2-To: 0123456780000
   Subject: Test Case
   Message-Id: <200207310834482A70BF63@\"~~foo~~\">
   Disposition-Notification-To: mrAS2@example.com
   Disposition-Notification-Options: signed-receipt-protocol=optional,
     pkcs7-signature; signed-receipt-micalg=optional,sha1
   Content-Type: multipart/signed; boundary="as2BouNdary1as2";
     protocol="application/pkcs7-signature"; micalg=sha1
   Content-Length: 2464


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   --as2BouNdary1as2
   Content-Type: application/edi-x12
   Content-Disposition: Attachment; filename=rfc1767.dat
     [ISA ...EDI transaction data...IEA...]

   --as2BouNdary1as2
   Content-Type: application/pkcs7-signature

     [omitted binary pkcs7 signature data]
   --as2BouNdary1as2--

   A.2 MDN for Message A.1 Above

   HTTP/1.0 200 OK
   AS2-From: 0123456780000
   AS2-To: "\"  as2Name  \""
   AS2-Version: 1.1
   Message-ID: <709700825.1028122454671.JavaMail@ediXchange>
   Content-Type: multipart/signed; micalg=sha1;
        protocol="application/pkcs7-signature";
        boundary="----=_Part_57_648441049.1028122454671"
   Connection: Close
   Content-Length: 1980

   ------=_Part_57_648441049.1028122454671

   & Content-Type: multipart/report;
   & Report-Type=disposition-notification;
   &    boundary="----=_Part_56_1672293592.1028122454656"
   &
   &------=_Part_56_1672293592.1028122454656
   &Content-Type: text/plain
   &Content-Transfer-Encoding: 7bit
   &
   &MDN for -
   & Message ID: <200207310834482A70BF63@\"~~foo~~\">
   &  From: "\"  as2Name  \""
   &  To: "0123456780000"
   &  Received on: 2002-07-31 at 09:34:14 (EDT)
   & Status: processed
   & Comment: This is not a guarantee that the message has
   &  been completely processed or &understood by the receiving
   &  translator
   &
   &------=_Part_56_1672293592.1028122454656
   &Content-Type: message/disposition-notification
   &Content-Transfer-Encoding: 7bit
   &
   &Reporting-UA: AS2 Server
   &Original-Recipient: rfc822; 0123456780000

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   &Final-Recipient: rfc822; 0123456780000
   &Original-Message-ID: <200207310834482A70BF63@\"~~foo~~\">
   &Received-content-MIC: 7v7F++fQaNB1sVLFtMRp+dF+eG4=, sha1
   &Disposition: automatic-action/MDN-sent-automatically;
   &  processed
   &
   &------=_Part_56_1672293592.1028122454656--

   ------=_Part_57_648441049.1028122454671
   Content-Type: application/pkcs7-signature; name=smime.p7s
   Content-Transfer-Encoding: base64
   Content-Disposition: attachment; filename=smime.p7s

   MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQ
   cp24hMJNbxDKHnlB9jTiQzLwSwo+/90Pc87x+Sc6EpFSUYWGAAAAAAAA
   ------=_Part_57_648441049.1028122454671--

      Notes:

   1. The lines proceeded with "&" is what the signature is
   calculated over.
   2. For details on how to prepare the multipart/signed with protocol =
   "application/pkcs7-signature" see the "S/MIME Message Specification,
   PKCS Security Services for MIME".)
   3. Note that the textual first body part of the multipart/report can
   be used to include a more detailed explanation of the error
   conditions reported by the disposition headers. The first body part
   of the multipart/report when used in this way, allows a person to
   better diagnose a problem in detail.
   4. As specified by RFC 3462 [9], returning the original or portions
   of the original message in the third body part of the
   multipart/report is not required. This is an optional body part.
   However, it is RECOMMENDED that this body part be omitted or left
   blank.

   A.3 Signed, encrypted message requesting a signed, asynchronous
   receipt

   Message-ID: <#as2_company#01#a4260as2_companyout#>
   Date: Thu, 19 Dec 2002 15:04:18 GMT
   From: me@example.com
   Subject: Async MDN request
   Mime-Version: 1.0
   Content-Type: application/pkcs7-mime;
     smime-type=enveloped-data; name=smime.p7m
   Content-Transfer-Encoding: binary
   Content-Disposition: attachment; filename=smime.p7m
   Recipient-Address: 10.240.1.2//
   Disposition-Notification-To:

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     http://10.240.1.2:8201/exchange/as2_company
   Disposition-Notification-Options: signed-receipt-protocol=optional,
    pkcs7-signature; signed-receipt-micalg=optional,sha1
   Receipt-Delivery-Option:
     http://10.240.1.2:8201/exchange/as2_company
   AS2-From: as2_company
   AS2-To: "AS2 Test"
   AS2-Version: 1.1
   Host: 10.240.1.2:8101
   Connection: close
   Content-Length: 3428

     [omitted binary encrypted data]

   A.4 Asynchronous MDN for Message A.3 Above

   POST / HTTP/1.1
   Host: 10.240.1.2:8201
   Connection: close, TE
   TE: trailers, deflate, gzip, compress
   User-Agent: RPT-HTTPClient/0.3-3I (Windows 2000)
   Date: Thu, 19 Dec 2002 15:03:38 GMT
   Message-ID: <AS2-20021219_030338@as2_company.dgi_th>
   AS2-Version: 1.1
   Mime-Version: 1.0
   Recipient-Address:
   http://10.240.1.2:8201/exchange/as2_company
   AS2-To: as2_company
   AS2-From: "AS2 Test"
   Subject: Your Requested MDN Response
   From: as2debug@example.com
   Accept-Encoding: deflate, gzip, x-gzip, compress, x-compress
   Content-Type: multipart/signed; micalg=sha1;
     protocol="application/pkcs7-signature";
     boundary="----=_Part_337_6452266.1040310218750"
   Content-Length: 3103

   ------=_Part_337_6452266.1040310218750
   Content-Type: multipart/report;
     report-type=disposition-notification;
     boundary="----=_Part_336_6069110.1040310218718"

   ------=_Part_336_6069110.1040310218718
   Content-Type: text/plain; charset=us-ascii
   Content-Transfer-Encoding: 7bit

   The message <x12.edi> sent to Recipient <AS2 Test> on Thu, 19 Dec
   2002 15:04:18 GMT with Subject <async MDN request> has been received,
   the EDI Interchange was successfully decrypted and its integrity was
   verified.  In addition, the sender of the message, Sender

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   <as2_company> at Location http://10.240.1.2:8201/exchange/as2_company
   was authenticated as the originator of the message. There is no
   guarantee however that the EDI interchange was syntactically correct,
   or was received by the EDI application/translator.

   ------=_Part_336_6069110.1040310218718
   Content-Type: message/disposition-notification
   Content-Transfer-Encoding: 7bit

   Reporting-UA: AS2@test:8101
   Original-Recipient: rfc822; "AS2 Test"
   Final-Recipient: rfc822; "AS2 Test"
   Original-Message-ID: <#as2_company#01#a4260as2_companyout#>
   Disposition: automatic-action/MDN-sent-automatically;
     processed
   Received-Content-MIC: Hes6my+vIxIYxmvsA+MNpEOTPAc=, sha1

   ------=_Part_336_6069110.1040310218718--

   ------=_Part_337_6452266.1040310218750
   Content-Type: application/pkcs7-signature; name=smime.p7s
   Content-Transfer-Encoding: base64
   Content-Disposition: attachment; filename=smime.p7s

   BhbWjEfbyXoTAS/H0zpnEqLqbaBh29y2v82b8bdeGw8pipBQWmf53hIcqHGM
   4ZBF3CHw5Wrf1JIE+8TwOzdbal30zeChw88WfRfD7c/j1fIA8sxsujvf2d9j
   UxCUga8BVdVB9kH0Geexytyt0KvWQXfaEEcgZGUAAAAAAAA=

   ------=_Part_337_6452266.1040310218750-

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed
   to pertain to the implementation or use of the technology
   described in this document or the extent to which any license
   under such rights might or might not be available; nor does it
   represent that it has made any independent effort to identify any
   such rights.  Information on the procedures with respect to
   rights in RFC documents can be found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use
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   specification can be obtained from the IETF on-line IPR repository
   at http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention
   any copyrights, patents or patent applications, or other

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   proprietary rights that may cover technology that may be required
   to implement this standard.  Please address the information to the
   IETF at ietf-ipr@ietf.org.

   Copyright (C) The Internet Society (2004). This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an
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   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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