RFC 1864 (rfc1864) - Page 3 of 4

The Content-MD5 Header Field

RFC 1864                Content-MD5 Header Field            October 1995


3. Processing the Content-MD5 field

   If the Content-MD5 field is present, a recipient user agent may
   choose to use it to verify that the contents of a MIME entity have
   not been modified during transport.  Message relays and gateways are
   expressly forbidden to alter their processing based on the presence
   of the Content-MD5 field.  However, a message gateway is allowed to
   remove the Content-MD5 field if the corresponding MIME entity is
   translated into a different content-type.

4. Security Considerations

   This document specifies a data integrity service that protects data
   from accidental modification while in transit from the sender to the
   recipient.  A secure data integrity service, such as that provided by
   Privacy Enhanced Mail [3], is conjectured to protect data from all
   modifications.

5. Acknowledgements

   This memo is based almost entirely on text originally written by
   Nathaniel Borenstein of Bellcore.  In addition, several improvements
   were suggested by Keith Moore of the University of Tennessee,
   Knoxville.

6. References

   [1] Borenstein, N., and N. Freed, "MIME (Multipurpose Internet Mail
       Extensions) Part One: Mechanisms for Specifying and Describing
       the Format of Internet Message Bodies", RFC 1521, Bellcore,
       Innosoft, September 1993.

   [2] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, MIT
       Laboratory for Computer Science and RSA Data Security, Inc.,
       April 1992.

   [3] Linn, J., "Privacy Enhancement for Internet Electronic Mail, Part
       I: Message Encryption and Authentication Procedures", RFC 1421,
       IAB IRTF PSRG, IETF PEM WG, February 1993.












Myers & Rose                Standards Track