"Content-Md5" in mail header sent by dtmail
2007-12-25 9:16:00
First of all, I have to thank for the prompt response from:
Matti Saarinen <mjs@butler.cc.tut.fi>
Michael F Gordon <Michael.Gordon@ee.ed.ac.uk>
Rich Kulawiec <rsk@itw.com>
Scott McDermott <scottm@kcls.org>
and the others that are still in the Net.
My original question:
> When I use dtmail to send mail, the mail header contains a line
> "Content-Md5", followed by some codes.
>
> My question is: what is the significance of this field? I know Md5 is a
> kind of security measures. But what can I, both as a sys-admin and an
> ordinary user, make use of this field?
>
> I have asked the above question in comp.unix.solaris, comp.security.unix and
> others. But I still can't get any answer. So would the experts here give me
> the hints?
The responses are as follow:
> From mjs@butler.cc.tut.fi Mon Jan 20 17:14:39 1997
> From: Matti Saarinen <mjs@butler.cc.tut.fi>
> Subject: Re: "Content-Md5" in mail header sent by dtmail
> To: wawong@asl.com.hk
> Date: Mon, 20 Jan 1997 11:12:08 +0200 (EET)
> You can verify that the content of the message has not been changed
> on its way by calculating md5-sum of the body of the message.
>
> From Michael.Gordon@ee.ed.ac.uk Mon Jan 20 17:37:35 1997
> From: Michael F Gordon <Michael.Gordon@ee.ed.ac.uk>
> X-At: Department of Electrical Engineering, The University of Edinburgh
> Date: Mon, 20 Jan 1997 09:34:45 GMT
> To: wawong@asl.com.hk
> Subject: Re: "Content-Md5" in mail header sent by dtmail
>
> > When I use dtmail to send mail, the mail header contains a line
> > "Content-Md5", followed by some codes.
> >
> > My question is: what is the significance of this field? I know Md5 is a
> > kind of security measures. But what can I, both as a sys-admin and an
> > ordinary user, make use of this field?
>
> The two RFCs included below explain what MD5 is and how it is used in
> the Content-Md5: header.
>
> Michael Gordon
>
By wales: the two RFCs are little bit large and are not attached here.
Request for Comments: 1321 and RFC 1864
> From edd@aic.net Mon Jan 20 19:00:34 1997
> Subject: Re: "Content-Md5" in mail header sent by dtmail
> To: wawong@asl.com.hk
> Date: Mon, 20 Jan 1997 13:49:24 +0300 (GMT)
> Cc: sun-managers@ra.mcs.anl.gov
> From: edd@acm.org
>
> MD5 is a message digest algorith invented by Ron Rivest of RSA Data Security
> and MIT LCS. MD5 reads a file of finite length and produces 128 bit hash.
> It is proved that this hash is very secure.
>
> In DTmail it is used to detect modified message body - when a message is created,
> its MD5 hash is computed and inserted in the headers. However, I don't
> know does dtmail checks it when receiving mail - you may want to check it
> yourself.
>
> Regards,
>
> Edgar
>
>
> PS For more info about MD5 et al visit www.rsa.com
>
>
> From rsk@itw.com Mon Jan 20 20:59:45 1997
> From: Rich Kulawiec <rsk@itw.com>
> Subject: Re: "Content-Md5" in mail header sent by dtmail
> To: wawong@asl.com.hk
> Date: Mon, 20 Jan 1997 07:58:12 -0500 (EST)
> X-Last-River: Brandywine
> X-Last-Cd: Duncan Shiek, "Duncan Shiek"
> Mime-Version: 1.0
> Content-Transfer-Encoding: 7bit
>
> It's a digital signature that provides a degree of assurance that the
> message contents have not been disturbed. See the various security-related
> FAQs which are regularly posted to Usenet's news.answers for full details.
>
>
> Rich Kulawiec
>
> From scottm@kcls.org Tue Jan 21 02:56:59 1997
> Date: Mon, 20 Jan 1997 10:54:32 -0800 (PST)
> From: Scott McDermott <scottm@kcls.org>
> X-Sender: scottm@rain
> To: Wales Wong <wawong@asl.com.hk>
> Subject: Re: "Content-Md5" in mail header sent by dtmail
> X-No-Archive: yes
> Mime-Version: 1.0
>
> On Mon, 20 Jan 1997, Wales Wong wrote:
>
> > When I use dtmail to send mail, the mail header contains a line
> > "Content-Md5", followed by some codes.
>
> I'm not sure, but my best guess would be that it's a checksum of the
> message so people can tell if it was modified from it's original form.
Best Regards,
Wales Wong
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