The following example describes what the MIME parts and message source will
look like for a signed message.
X-Mailer: Microsoft Outlook Express 4.71.0729.0
From: "Ryan LaBrie" <ryanl@microsoft.com>
To: "steven@somecompany.com" <steven@somecompany.com>
Subject: signed message
Date: Wed, 30 Apr 1997 20:37:03 -0700
X-Priority: 3
X-MSMail-Priority: Normal
MIME-Version: 1.0
Content-Type: multipart/signed;
boundary="----=_NextPart_000_01BC55A9.8FA8A740";
micalg=sha1;
protocol=application/x-pkcs7-signature
X-MimeOLE: Produced By Microsoft MimeOLE Engine V4.71.0728.0
NOTE - This is a multi-part message in MIME format.
------=_NextPart_000_01BC55A9.8FA8A740
Content-Type: multipart/alternative;
boundary="----=_NextPart_001_01BC55A9.8FAA2DE0"
------=_NextPart_001_01BC55A9.8FAA2DE0
Content-Type: text/plain;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
NOTE - This is a clear signed message.
------=_NextPart_001_01BC55A9.8FAA2DE0
Content-Type: text/html;
charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML 3.2//EN"><HTML>
<HEAD>
<META HTTP-EQUIV=3D"Content-Type" CONTENT=3D"text/html; =
charset=3DUS-ASCII">
<META content=3D'"Trident 4.71.0729.0"' name=3DGENERATOR>
</HEAD>
<BODY>
<P><FONT SIZE=3D2 FACE=3D"Arial">This is a clear signed message =
hopefully...</FONT></P>
</BODY>
</HTML>
------=_NextPart_001_01BC55A9.8FAA2DE0--
------=_NextPart_000_01BC55A9.8FA8A740
Content-Type: application/x-pkcs7-signature;
name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="smime.p7s"
MIIGTAYJKoZIhvcNAQcCoIIGPTCCBjkCAQExCzAJBgUrDgMCGgUAMAsGCSqGSIb3DQEHAaCC
BTsw
ggU3MIIEoKADAgECAhBO9j8bsMhfLRsKSiktdU5hMA0GCSqGSIb3DQEBBAUAMGIxETAPBgNV
BAcT
CEludGVybmV0MRcwFQYDVQQKEw5WZXJpU2lnbiwgSW5jLjE0MDIGA1UECxMrVmVyaVNpZ24g
Q2xh
c3MgMSBDQSAtIEluZGl2aWR1YWwgU3Vic2NyaWJlcjAeFw05NzAyMjAwMDAwMDBaFw05ODAy
MjAy
. (lots of content deleted)
------=_NextPart_000_01BC55A9.8FA8A740--
The last part of the message is the signed hash of the message and is sent
using the content-transfer-encoding type of Base64 which will allow the
transmission of 8-bit data encoded in a 7-bit format. Hence, it is quite
unreadable. This part of the message is listed as an attachment with the
filename smime.p7s. Mail clients that are not S/MIME aware will display
this file as an attachment. If the message is received by an S/MIME aware
client, there will not be a visible attachment. In addition, in the above
message, the certificate was included and would be available for importing
into the Windows Address Book.