Uneditable Mail (OL 2000/2003)

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We need to send to the organizations we work with an e-mail with a certain notification. This notification has a list of files they are supposed to send us. We want to make sure no one can modify this list. We thought of different alternatives:

a) Attaching the list in a suitable text file, computing a hash of this file and sending the hash value in the e-mail so if they modify the text file they won’t be able to generate the same hash.
Sending a digitally signed e-mail containing the list either plainly typed or within an attached file.
c) A combination of a) and .

The problems we fear might arise, respectively, are:
a) That someone might tamper with the attachment, generate the modified file’s hash value and modify the hash value stated in the e-mail. I know that Outlook mails properties (File | Properties) show if and when the message has been modified (e.g. via Edit | Modify). But I don’t know if all mail clients are so trustworthy.
This is my short experience with signed mail: Outlook will show if the message has been tampered with in any form. That is, if it’s been manually edited of modified by some program (e.g.: Anti Virus software, Anti-Spam software, etc). What I don’t know is, again, if all mail clients are so trustworthy / compatible with digital signatures.

I also thought of an alternative involving PGP, but if possible I’d prefer not to force recipients to have PGP installed. It’s an alternative I would consider, though.

What do you think? Any suggestions?

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Why not just send them a link to a (secure) page on your website. That would need to be hacked into to change the list.

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Hi Leif,

It’s a good alternative (hadn’t thought of that), but if possible we’d like the system to be more transparent. That is, our recipients have no guarantee that we will not change the list in the web site without notice. As a rather formal notification, we’d want something both parties can rely on. As if it were a printed notification, but in electronic format.

Thanks for the suggestion

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You could send a “Screen shot” image of the files listing, then one would have to edit the image and not just a few letters of text.

DaveA I am so far behind, I think I am First
Genealogy....confusing the dead and annoying the living

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Hi Dave,

I’d thought about that, but the list is about 20 pages long and the only way I know to convert such a long text file is via IrfanView, saving the data in the TXT format, opening the TXT with IView, and saving as an image format (JPG for example).
It would be difficult to modify the image, but it can be done, and I wanted the procedure to be as trustworthy as possible, so I decided to ask for your advice
I had also thought of PDFing the image, so the recipient wouldn’t be able to alter text very easily (not even if they got to know/crack the PDF password). But IView crams the whole list in a single JPG that gets printed in a single PDF page, which results in the output PDF being illegible.

In any case, as time passes by and I get a taste of all your ideas, my paranoia tends to cease

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Sounds like you need to invest in to a GOOD well protected PDF program such as Adobe Acrobat. The investment will save you a lot work and headaches.

DaveA I am so far behind, I think I am First
Genealogy....confusing the dead and annoying the living

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You have no guarantee your recipients are going to receive your emails, let alone read them!

I don’t quite follow the need for guarantees, and it may be difficult for you to explain the setup that you require. I can still see pitfalls whatever route you take. Is there a difference between you updating the list on a web-page without telling them, and you emailing them notification which they don’t receive?

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You have no guarantee your recipients are going to receive your emails, let alone read them!

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[/indent]You make a point there. As things are now, it seems we’ll try to make do with something in the short run until we can implement a user-based site (perhaps a not user-based site).
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I can still see pitfalls whatever route you take. Is there a difference between you updating the list on a web-page without telling them, and you emailing them notification which they don’t receive?

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[/indent]Several organizations are to send us certain attachments periodically and on schedule.
When we receive their attachment, we want to send them a receipt. We also want to send them a warning of which files we have not received in due time. I know the whole scheme isn’t totally reliable as it’s internet-based, but this is the way it was designed a while ago. The reception of the attachments is somewhat critical, as it triggers payments to the organizations. That’s why I wanted to make as sure as possible that someone couldn’t alter the contents of the receipts, in case a recepient might try to tamper with mail contents to take legal actions. In a nutshell, we warn them we have not received a certain attachment, they alter the mail contents so it reads we have received the purported attachment and they sue us for not having payed them.

Our idea is, however, to move to a web-based file-upload system.

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Along the lines of DaveA’s suggestion, could you send a document with hyperlinks which is password protected to open?

In the US documents which contain personal medical information must by law be kept very secure; for such information my company uses this service:
http://www.zixcorp.com[/url%5D

The product my company uses basically sends a non-secure e-mail requesting the recipient to log in to a secure site and get the ‘real’ message from a web-based mail system. I have no idea how much it costs, I assume it’s not cheap, but I expect that my company reviewed the market and found it to be the best combination of price and security. You’ll see a lot of well-known US health, health insurance, and banking companies listed in the “SuccessStories” section/applet.

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In the US documents which contain personal medical information must by law be kept very secure

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[/indent]Good to know that. Our traffic does not include such information. AFAIK, in Argentina there is not such a well-establish body of legislation (there’s a kind of legal gap). Over the last years there have been some improvements on digital signatures, and at this very moment legislators seem to be working on it. Hopefully things will be tidier some time from now.

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