E-Mail Clients That Support X.509 Digital IDs?
"I have already checked a previous Ask Slashdot on this, as the title would suggest being close, but it seems to be more about sending anonymous e-mail through a secure POP/SMTP connection for an ISP which is a tad different and a tad more complicated than my needs.
In my particular case, I have this Digital ID that confirms that any mail a recipient gets is actually sent from me. The way it works, every time I send mail, it pops up a dialog and asks for my password. After confirmation, it encrypts the contents and attaches a security certificate that the recipient can view to confirm authenticity. In this way, even someone on my machine can't send mail as me. The certificate allows me to encrypt mail also, so only people that have my specific key can read it. It has several other useful features as well. (Here's a quick FAQ link)
I have to do this because, at work, I deal with about 100 developers that live in an unnamed former Soviet bloc country, and are QUITE security concious. The Verisign DigitalID allows them to be sure that the mail they are getting comes from me. It's quite cool, and I would LOVE to have this capability in Linux. Unfortunately, there seem to be no solutions to this problem, at least none that are obvious."
S/MIME is the way to do email with X509 certificates, and Netscape Communicator is one mail app which uses S/MIME.
You can manipulate S/MIME messages (encrypt, decrypt, sign, verify) using OpenSSL at the command line. I'd love to see mutt hacked to front-end OpenSSL smime the way it can with PGP.
There are those who would argue that X509 is evil, thanks to its strict hierarchical structure (where Verisign's root CA is the big daddy of everything), and that only PGP gives the power to the people -- but from a pragmatic point of view, X509 is everywhere thanks to SSL etc. and if you want to be able to do secure email with the world, S/MIME is the way to go. PGP is attempting to converge with the S/MIME standard in any case.
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x.509 is typically used with a message format called S/MIME. Recent versions of Netscape Communicator have a facility for sending, receiving, encrypting, and decrypting S/MIME messages using x.509 certificates.
If you use a flexible mail program such as mutt, you can pipe your message through the openssl smime command. By canning openssl smime with the options -encrypt, -decrypt, -sign, and -verify, you can perform all the same operations you could with a client that supported S/MIME natively.