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Re: secure sign & encrypt

2002-05-21 05:59:02

----- Original Message -----
From: "Terje Braaten" <Terje(_dot_)Braaten(_at_)concept(_dot_)fr>
To: <ietf-openpgp(_at_)imc(_dot_)org>
Sent: Monday, May 20, 2002 7:31 PM
Subject: RE: secure sign & encrypt


The problem is that most users when they decrypt a message
that is signed, they will think they can be sure the signer
and the encrypter is the same person/entity.
It would be a major improvement in the OpenPGP specification
to allow applications to ensure that that really is the case.


Functionally, that is the case now in Open PGP.

Even though a signed and encrypted message can be separated into a
verifiable free standing signed message, and then
re-encrypted and sent on to someone else,
it 'cannot' {afaik} be re-combined into a signed and encrypted message that
appears the same as a de-novo signed and encrypted message.

The most that can be done with the separation and re-encryption, is to have
a message, that upon decryption, is clearsigned,
or armored signed, and even the armored signed message is clearly of a
different form than a de novo armored signed message;
{a de novo armored signed message always has the message block begin with
the letters 'ow', the separated armored signed
message never does}.

Someone receiving a re-encrypted separated signed message, can instantly
tell upon decryption, that it was an 'intentionally'
re-encrypted message, and not an original.

The only time that this could be a problem, is for very new users, who may
inadvertently get into a habit of clearsigning and then encrypting, instead
of using the one-function 'sign and encrypt' , and as soon as it is pointed
out to them that it is simpler and easier to use 'sign and encrypt' single
function, they will probably do so.



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