problems opening .asc file

Daniel Kahn Gillmor dkg at fifthhorseman.net
Fri Sep 6 15:44:35 CEST 2013


Hi Matt--

On 09/05/2013 09:35 PM, Matt D wrote:

> i was sent a .asc file as an attachment.

It sounds like you may have been sent a PGP/MIME-signed message.  The
message i'm sending now is PGP/MIME-signed.  These kinds of messages
show up in some Mail User Agents that don't know about PGP/MIME as
though it is a message with an attachment, instead of a single signed
message.

In fact, the signature part is not an "attachment" in the traditional
sense of the word, and it can only be evaluated in the context of the
message it was sent with.

For more detail on PGP/MIME, see https://tools.ietf.org/html/rfc3156

> when i try to open it it says
> "Couldn't decrypt file: No data"

this is probably because the data it is signing is missing (i.e. you are
evaluating the signature without the message body itself)

> What am i doing wrong here?

If you want to be able to verify these message signatures, you should
set yourself up with a Mail User Agent that can handle PGP/MIME-signed
messages.  Some examples are:

 * thunderbird with the enigmail plugin
 * evolution
 * claws mail
 * outlook with gpgOL (http://gpg4win.org/about.html)
 * notmuch

hth,

	--dkg

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