[TLS] Protocol version bit to use, was Justification for "Ugly Dirty Hack"

[Bill Frantz <frantz at pwpconsult.com>]

mike-list at pobox.com (Michael D'Errico) on Thursday, November 19, 2009 wrote:

>My suggestion is to set the upper bit of the minor version field.
>This provides a clear and unmistakable signal to the client, and is
>completely contained within the 0x03 major version number space.  Is
>it a "hack", yeah, but it's entirely reasonable.

If I understand the minor version field correctly, there are 5 or 6 bits
that are always sent as zero by all current versions of TLS/SSL. Any of
them would be suitable as a S->C signal.

There may be advantages to using bits other than the 0x80 bit. For example,
if the 0x04 bit is available, then it could be used for the signaling
requirement, leaving 0x08 and higher available for future versions of TLS.
This approach would still leave a simple ordered compare available for
selecting the "most recent" protocol version both ends support.

Cheers - Bill

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Bill Frantz        |"After all, if the conventional wisdom was working, the
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