[rfc-i] Unicode characters for ASCII control characters

Phillip Hallam-Baker phill at hallambaker.com
Wed Jun 3 10:28:59 PDT 2015

On Wed, Jun 3, 2015 at 1:06 PM, Paul Hoffman <paul.hoffman at vpnc.org> wrote:

> On Jun 3, 2015, at 9:54 AM, Nico Williams <nico at cryptonector.com> wrote:
> >
> > On Wed, Jun 03, 2015 at 12:33:33PM -0400, Phillip Hallam-Baker wrote:
> >>> On 6/3/15 9:02 AM, Phillip Hallam-Baker wrote:
> >>>> Does anyone know if there is a defined unicode character for
> >>>> 'printable non-printable' ? I had a look and could not see
> >>>> anything.
> >>
> >> Found it! U+241E
> >> ␞
> >>
> >> I think this should allow a lot more useful examples when writing specs
> >> with significant CRLF sequences.
> >
> > Very nice!
> If we put the actual U+241E character in an RFC so that people can "see"
> the character, many people will copy-and-paste it into the programs,
> instead of using an U+001E character. I cannot imagine how you can word the
> surrounding text well enough to make it clear that you're just showing a
> character that you don't want them to copy-and-paste.
> We have not heard any problems so far with people misunderstanding RFC
> 7464 and copying in the six characters "U+001E", or the four characters
> "001E", or even the two characters "RS". The proposal above seems likely to
> cause way more problems than it would fix.
> If you absolutely need to indicate that character as a single unit among
> other characters, in the upcoming v3 RFC format, you can include SVG
> artwork, and that artwork can use a little picture for RS (and for LF,
> which is also useful for RFC 7464 examples). That artwork would be quite
> clear and no one would expect to be able to copy-and-paste from the artwork.

Not sure how you use examples Paul. I don't find cutting and pasting them
into Visual Studio causes code to be emitted.

The type of situation I would see them being useful is as follows:

Example of message signing

If the JSON header and message is

{ "protected" : "askfkjh"
  "signature" : "aslkdqwlkjhdfjkl" }
␞␍␊{"operation" : ...}

The signature is calculated over the byte sequence:
␍␊{"operation" : ...}

Note that this is an example, not a substitute for precise text. But both
are usually required.
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