Subject: [TLS] [Editorial Errata Reported] RFC6347 (4642)

From: RFC Errata System <[email-masked]>
Date: Fri, 18 Mar 2016 12:41:26 -0700 (PDT)

The following errata report has been submitted for RFC6347,
"Datagram Transport Layer Security Version 1.2".

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You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=6347&eid=4642

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Type: Editorial
Reported by: Dale R. Worley <[email-masked]>

Section: 4.1

Original Text
-------------
   version
      The version of the protocol being employed.  This document
      describes DTLS version 1.2, which uses the version { 254, 253 }.
      The version value of 254.253 is the 1's complement of DTLS version
      1.2.  This maximal spacing between TLS and DTLS version numbers
      ensures that records from the two protocols can be easily
      distinguished.  It should be noted that future on-the-wire version
      numbers of DTLS are decreasing in value (while the true version
      number is increasing in value.)

Corrected Text
--------------
Replace "1's complement of DTLS version" with "1's complement
of TLS version":

   version
      The version of the protocol being employed.  This document
      describes DTLS version 1.2, which uses the version { 254, 253 }.
      The version value of 254.253 is the 1's complement of TLS version
      1.2.  This maximal spacing between TLS and DTLS version numbers
      ensures that records from the two protocols can be easily
      distinguished.  It should be noted that future on-the-wire version
      numbers of DTLS are decreasing in value (while the true version
      number is increasing in value.)

Notes
-----
Clearly this won't confuse the reader, but it is incorrect as written and should be corrected at some time.

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RFC6347 (draft-ietf-tls-rfc4347-bis-06)
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Title               : Datagram Transport Layer Security Version 1.2
Publication Date    : January 2012
Author(s)           : E. Rescorla, N. Modadugu
Category            : PROPOSED STANDARD
Source              : Transport Layer Security
Area                : Security
Stream              : IETF
Verifying Party     : IESG

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From: Henrik Grubbström <[email-masked]>
Date: Mon, 21 Mar 2016 16:37:15 +0100

> "Datagram Transport Layer Security Version 1.2".

As far as I can see, the original text is correct, which is easy to
see if you look at the corresponding paragraph of RFC 4347 (DTLS 1.0):

    version
      The version of the protocol being employed. This document describes DTLS
      Version 1.0, which uses the version { 254, 255 }. The version
value of 254.255
      is the 1's complement of DTLS Version 1.0.

If the suggested text had been correct, then the encoding in RFC 4347
would have been { 254, 254 } as DTLS 1.0 is based on TLS 1.1.

-- 
Henrik Grubbström                                       [email-masked]
Roxen Internet Software AB                              [email-masked]

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From: [email-masked] (Dale R. Worley)
Date: Tue, 22 Mar 2016 14:17:19 -0400

<[email-masked]> writes:
>       describes DTLS Version 1.0, which uses the version { 254, 255 }.
>       The version value of 254.255 is the 1's complement of DTLS
>       Version 1.0.
>

You're right, { 254, 255 } is the complement of { 1, 0 }, so the erratum
must be incorrect.

Oddly, the following sentence in RFC 4347 is factually incorrect as an
architectural statement but is correct as a description of the protocol:
"This maximal spacing between TLS and DTLS version numbers ensures ..."
The Hamming spacing isn't maximal, that would be obtained with { 254,
254 }, but it is the value that is used and it does ensure that the
protocols are easily distinguished.

Dale