Lines Beginning with "From" Dash-Escaped?

[Ingo Klöcker]

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On Saturday, 28. April 2001 04:35, Nick Andriash wrote:
> Strange, but I just noticed that both PGP and GPG insert a dash/space
> (dash-escape) at the start of a line beginning with "From". I never
> noticed that before, and although I do realize that some Mail Clients
> used to use "From" as a delimiter, I never thought PGP/GPG would
> dash-escape it.
>
> The dash/space is only applied if "From" starts a sentence, and the
> word must be capitalised. "From" by itself is not affected. Below is
> an example of what I mean:
> With both PGP and GPG involved, I thought this must be part of RFC
> 2440 so I looked through it and found Section 7.1/Dash-Escaped Text.
> It hints at PGP applying the dash-escape to "From" lines because some
> MUA change these lines to ">From", so therefore GPG should follow.
> Although I've heard of some MUA's that use "From" as a delimiter,
> I've never seen it used.
>
> Can anyone expand on the reasons why PGP and GPG use the dash-escape
> in this manner, aside from what is written in the RFC?

I found this in the NEWS:

Noteworthy changes in version 0.9.0 ----------------------------------- 
[snip]
    * New option --escape-from-lines to "dash-escape" "From " lines to  
	prevent mailers to change them to ">From ".  This is not enabled by    
	default because it is not in compliance with rfc2440 - however, you
	should turn it on.

Reason:
If a MUA uses the mailbox format, i.e. a simple text file where all 
messages are stored one after the other a line starting with "From " is 
used to mark the start of the next message. There are a lot of MUAs 
which use the mailbox format, for example Netscape Messenger, KMail and 
also Pine and Mutt.
Now if a line inside a message starts with "From " it will be changed 
to ">From " by the MUA while receiving the mail. But this additional 
">" would break the signature. Therefore PGP and GnuPG dash-escape the 
"From " if they clear-sign messages.

The reason why you never have seen a line beginning with ">From " might 
be because the MUA automatically removes the ">" before displaying the 
mail. The ">" can only be found in the mailbox file in which the 
message is stored.

I hope this clears things up.

Regards,
Ingo
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