From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.io/gmane.emacs.gnus.general/55123 Path: main.gmane.org!not-for-mail From: Nathan Sullivan Newsgroups: gmane.emacs.gnus.general Subject: Re: Encrypting outgoing message but not Gcc? Date: Sun, 07 Dec 2003 03:07:03 -0800 Sender: ding-owner@lists.math.uh.edu Message-ID: <87zne43mzs.fsf@shampoo.pants.nu> References: <87vfot99o1.fsf@virgil.koldfront.dk> <87r7zh8k9h.fsf@virgil.koldfront.dk> NNTP-Posting-Host: deer.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: sea.gmane.org 1070795284 31754 80.91.224.253 (7 Dec 2003 11:08:04 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Sun, 7 Dec 2003 11:08:04 +0000 (UTC) Original-X-From: ding-owner+M3663@lists.math.uh.edu Sun Dec 07 12:08:02 2003 Return-path: Original-Received: from malifon.math.uh.edu ([129.7.128.13]) by deer.gmane.org with esmtp (Exim 3.35 #1 (Debian)) id 1ASwld-0000HD-00 for ; Sun, 07 Dec 2003 12:08:02 +0100 Original-Received: from localhost ([127.0.0.1] helo=lists.math.uh.edu) by malifon.math.uh.edu with smtp (Exim 3.20 #1) id 1ASwky-00006H-00; Sun, 07 Dec 2003 05:07:20 -0600 Original-Received: from justine.libertine.org ([66.139.78.221] ident=postfix) by malifon.math.uh.edu with esmtp (Exim 3.20 #1) id 1ASwko-000069-00 for ding@lists.math.uh.edu; Sun, 07 Dec 2003 05:07:10 -0600 Original-Received: from cynthia.pants.nu (adsl-216-102-214-42.dsl.snfc21.pacbell.net [216.102.214.42]) by justine.libertine.org (Postfix) with ESMTP id 699983A0043 for ; Sun, 7 Dec 2003 05:07:09 -0600 (CST) Original-Received: from shampoo.pants.nu (adsl-216-102-214-46.dsl.snfc21.pacbell.net [216.102.214.46]) by cynthia.pants.nu (Postfix) with SMTP id AA4AC2C030 for ; Sun, 7 Dec 2003 03:07:08 -0800 (PST) Original-Received: by shampoo.pants.nu (sSMTP sendmail emulation); Sun, 7 Dec 2003 03:07:03 -0800 Original-To: ding@gnus.org In-Reply-To: <87r7zh8k9h.fsf@virgil.koldfront.dk> ( =?iso-8859-1?q?Adam_Sj=F8gren's_message_of?= "Sun, 07 Dec 2003 02:54:50 +0100") User-Agent: Gnus/5.1002 (Gnus v5.10.2) XEmacs/21.4 (Common Lisp, linux) Precedence: bulk Xref: main.gmane.org gmane.emacs.gnus.general:55123 X-Report-Spam: http://spam.gmane.org/gmane.emacs.gnus.general:55123 spamtrap@koldfront.dk (Adam Sj=F8gren) writes: > On Sat, 06 Dec 2003 13:35:21 -0500, Lloyd wrote: > >> Also, I think there's a gap somewhere in my understanding of all >> this. How can it be that something encrypted twice, once with the >> recipient's public key and once with yours, would only need your >> private key to be decrypted? Wouldn't there have to be two >> decryptions, one for each of the previous encryptions? Or in this >> case, is the encryption done with some sort of mathematical >> combination of both public keys, such that either corresponding >> private key can decrypt it? > > I'm not able to adequately and comprehensibly explain the theory, but > I think it's a proporty of either assymetric key cryptography in > general or the way PGP/GnuPG is constructed (the latter being less > likely, probably, perhaps). It's a property of the way almost all assymetric cryptography is implemented. The problem is that public key encryption is grotesquely slow, so programs like PGP/GPG don't encrypt the entire message with the public key. Instead, they encrypt the message with a symmetric cypher, like IDEA or Blowfish, then encrypt the symmetric key with the public key for the desired recipient. If you have multiple recipients, then multiple copies of the encrypted symmetric key are included, each encrypted for a specific public key pair. --=20 Nathan Sullivan alfonso@pants.nu ---------------------------------------------------------------------------= ---- Conscience is what hurts when everthing else feels so good.