Feature suggestion: options to require MDC or trusted signature on decryption

[Holger Smolinski via [gnupg-devel]]

Am 24.05.2018 um 22:34 schrieb Uri Blumenthal:
> I do *not* want to enforce the presence of a signature (to preserve the possibility of anonymity) - but I do want a true AE.

+1 - anonymity is important, and AE is the way to prohibit variant 2
(the one with gadget injection)

variant 1 (wrapping) is more difficult to handle, as secured content is
presented and parsed in a potentially unsecured environment. Any
solution will have to ensure, that the entire message (including the
non-encrypted parts) has not been modified between the sender and the
recipient.

I'd suggest clients to wrap any (partially) encrypted message in a fully
encrypted (and AE'ed by the sender) single part envelope message, and
consequently neverever parse any surroundings of an encrypted envelope
beyond decrypting the contents of that single part.
At least that will secure future messages against variant 1 leaks -
messages stored unpacked from the envelope (like old stored messages)
will still be vulnerable.

Regards
	Holger

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