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The Content-MD5 Header Field (RFC1544)

IP.com Disclosure Number: IPCOM000002376D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 3 page(s) / 6K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Rose: AUTHOR

Abstract

This memo specifies an optional header field, Content-MD5, for use with MIME-conformant messages.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 49% of the total text.

Network Working Group M. Rose

Request for Comments: 1544 Dover Beach Consulting, Inc.

Category: Standards Track November 1993

The Content-MD5 Header Field

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Abstract

This memo specifies an optional header field, Content-MD5, for use

with MIME-conformant messages.

Table of Contents

1. Introduction .......................................... 1

2. Generation of the Content-MD5 Field ................... 2

3. Processing the Content-MD5 field ...................... 2

4. Security Considerations ............................... 3

5. Acknowledgements ...................................... 3

6. References ............................................ 3

7. Author's Address ...................................... 3

1. Introduction

Despite all of the mechanisms provided by MIME [1] which attempt to

protect data from being damaged in the course of email transport, it

is still desirable to have a mechanism for verifying that the data,

once decoded, are intact. For this reason, this memo defines the use

of an optional header field, Content-MD5, which may be used as a

message integrity check (MIC), to verify that the decoded data are

the same data that were initially sent.

MD5 is an algorithm for computing a 128 bit "digest" of arbitrary-

length data, with a high degree of confidence that any alterations in

the data will be reflected in alterations in the digest. The MD5

algorithm itself is defined in [2]. This memo specifies how the

algorithm may be used as an integrity check for MIME mail.

2. Generation of the Content-MD5 Field

The Content-MD5 field is generated by only an originating user agent.

Message relays and gateways are expressly forbidden from generating a

Content-MD5 field.

Use of the Content-MD5 field is completely optional, but its use is

recommended whenever data integrity is desired, but Privacy-Enhanced

Mail services [3] are not available. (Consult Section 4 for further

details.) The Content-MD5 field may only be added to MIME entities of

a `leaf' nature, i.e., the Content-MD5 field may be used with any

content type other than multipart or message/rfc822.

To generate the value of the Content-MD5 field, the MD5 algorithm is

computed on the canonical form of the data. In particular, this

means that the sender applies the MD5 algorithm on the raw data,

before applying any content-transfer-encoding, and that the receiver

also applies the MD5 algorithm on the raw data, after undoing any

conten...