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Transfer between servers is over SMTP, which is not encrypted by default and almost always subject to degradation attacks (the MITM can claim not to support STA
by jedbrown 13y ago
Transfer between servers is over SMTP, which is not encrypted by default and almost always subject to degradation attacks (the MITM can claim not to support STARTTLS). In any case, the user cannot verify or demand that STARTTLS be used and many hosts don't support it at all. Meanwhile, PGP does not require any trust of intermediate entities, but relatively few people you might want to email have PGP keys and even those with keys might not have them on the device from which they intend to read your email. S/MIME is in a similar position to PGP, with a CAs trust model instead of Web of Trust.
- andrewaylett 13y agoNote that this is indeed almost always, rather than actually always. My mail server is configured to refuse to send to Google (and a few other hand-picked sites) unless protected by SSL. The converse is, unfortunately, not yet true. DANE[0] should allow me to put DNSSEC secured records in place to tell Google (et al) that they should always use SSL to talk to me too, but I don't have DNSSEC support for my domains yet and my version of Postfix isn't new enough to be able to use it for outgoing mail either. More frustratingly, many popular email providers (for example, BT) don't support SSL at all. That lowers the bar for eavesdropping from active MITM to passive listening. 0: http://www.internetsociety.org/deploy360/resources/dane/ http://www.internetsociety.org/deploy360/resources/dane/