On 2020-08-28 17:53, Grant Taylor wrote: > On 8/28/20 3:33 PM, Michael Orlitzky wrote: >> TLS only secures the channel; what comes out at the end is a plain-text >> message that can be read with minimal effort by the VPS provider, >> no skullduggery needed. > > I agree that STARTTLS only protects the email while it's in flight > between servers. > > Though I do think that it's going to somewhat difficult for a VPS > provider to read the contents of the message if it's stored on an > encrypted disk.
The contents of the disk are unencrypted while the server is powered on, or at least while the server is receiving email (while it's reading from and writing to that disk). In practice that will be all the time -- you can't log in and type the disk-encryption password every time an email arrives. >> Unless the sender and recipient have some pre-shared secret (like GPG >> assumes), > > I *REALLY* thought that PGP (GPG) was based on public & private key > pairs, much like S/MIME and TLS. > > As such, Alice and Bob can encrypt messages to each other, even through > an untrusted medium such as a questionable email server. > > Yes, that still leaves the bootstraping issue of how do Alice and Bob > get each other's public key. -- I defer to my recent comments about > publishing keys in DNS and relying on DNSSEC. > GPG is based on public keys, but you've anticipated my response: public-key encryption still requires you to verify that "my" public key does in fact belong to *me* somehow. If you believe in the web of trust, then someone you know (or someone someone you know knows...) has to have met me in person and signed my key before it means anything to you. I shouldn't have used the word "secret." Pre-established or out-of-band authentication would have been more accurate. With GPG, the trust is between you and I, and the VPS provider acts as the eavesdropper. All three parties are distinct, and the security can work. With TLS between MTAs, the trust is established on-the-fly between the other MTA and the VPS provider, but the VPS provider still also plays the the role of the eavesdropper. When the eavesdropper is trusted, you're in trouble.
