Re: On email and web security

[Doug Barton <[e-mail]>]

On 01/13/2016 12:23 AM, Dave Cridland wrote:
> When senders send to the proxy, they're encrypting in a special way
> which means that the proxy can't decrypt; instead it can only re-key the
> message to each member. The proxy also cannot add other keys (including
> its own), so cannot just add itself as a member and decrypt the result.
> Members receive the message, and thanks to the crypto-fairies, they see
> it as signed by the sender. I like to think of this as a special-case of
> homomorphic encryption, but only so I can sound like I know what I'm
> talking about.

I don't see any way that this could work using PGP, but I confess I 
don't know enough about S/MIME to know if it could be done using it or not.

Doug