Note on S/MIME Signature Verification

M. Gallant 07/01/2002
To manually verify a signed S/MIME message with detached content, the entire MIME entity representing the content must be passed to the verification routine. In the full S/MIME email sample appended below, the MIME entity that is actually signed is: 
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Test
where a final CR/LF is included in the data to be hashed/signed. If the content to be signed for S/MIME is binary or not 7 bit ASCII, the data is transfer encoded, typically as BASE64 which is then signed, packaged as pkcs #7, base64 encoded and finally wrapped as a MIME entity application/x-pkcs7-signature, similar to the text content sample below.
CDO facilitates constructing, signing and verification of S/MIME messages.

To: "Mitch Gallant" <neutron@istar.ca> Subject: Signed from OE Date: Sun, 30 Jun 2002 15:12:08 -0400 MIME-Version: 1.0 Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg=SHA1; boundary="----=_NextPart_000_0012_01C22048.805E6800" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Mozilla-Status: 8009 X-Mozilla-Status2: 00000000 X-UIDL: 5ec7c9d390588171ba025db7cd30de8e This is a multi-part message in MIME format. ------=_NextPart_000_0012_01C22048.805E6800 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Test ------=_NextPart_000_0012_01C22048.805E6800 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIKGDCCAjww 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