It shows that what you sent hasn't been modified subsequently. It links a message to YOU, and it not only says you are who you are, but that you DID say what's in the email.
Given how easy it is to edit an email after delivery, you can't really trust email for anything contractual without a certificate by way of proof.
MD5 files have existed for a long time as signatures for emails and also for downloads from websites.
Perversely certificate signing has been commonplace in Linux for a long time, perhaps because Linux was written by geeks who understood the value of the process and built it in.
An awful lot of the confusion is caused by multiple 'standards' on the windows platform - please don't treat this as a Microsoft attack because it's incompatibilities with third parties that's the real prob.
Discussion on:
Message 7 of 1
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