1.5", RFC 2313, March 1998. 9. RFC 1421 Linn, J., "Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures", RFC 1421, February 1993. 10. RFC 1422 Kent, S., "Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management", RFC 1422, February 1993. 11. RFC 1423 Balenson, D., "Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers", RFC 1423, February 1993. 12. RFC 2045 Freed N. & Borenstein N., “Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies”, RFC 2045, November 1996. 13. RFC 2046 Freed N. & Borenstein N., “Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types”, RFC 2046, November 1996. 14. RFC 2047 Moore K., “Multipurpose Internet Mail Extensions (MIME) Part Three: Header Extensions for Non-ASCII Text”, RFC 2047, November 1996. 15. RFC 2048 Freed N., Klensin J., Postel J., “Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures”, November 1996. 16. RFC 2049 Freed N. & Borenstein N., “Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples”, RFC 2049, November 1996.