From gnupg-users  Tue Mar 13 19:51:33 2012
From: Ingo =?iso-8859-15?q?Kl=F6cker?= <kloecker () kde ! org>
Date: Tue, 13 Mar 2012 19:51:33 +0000
To: gnupg-users
Subject: Re: Symmetric encryption - options?
Message-Id: <201203132051.40931 () thufir ! ingo-kloecker ! de>
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On Tuesday 13 March 2012, jpemail2001-321@yahoo.com wrote:
> >It isn't RSA because this is symmetric encryption.  CAST5 is a
> >128-bit block cypher.
>=20
> So its not really safe, is it?

Why do you think so? Define "really safe".


> @Robert
>=20
> >If you choose to use someone's public certificate to encrypt a
> >message, they use the private part of that certificate to decrypt
> >it -- different things for encryption and decryption, thus a
> >different kind of algorithm, an asymmetric one, is used.So you
> >would suggest, to use RSA? I think so because it seems to be
> >stronger encryption.
>=20
> The problem is I need to encrypt a message but I dont know the
> recipient yet. So I considered a passphrase method. Cause he dont
> need to send me his public key (if he has any).
>=20
> But.... OK I will try to encrypt the message with a new created
> private key (specially created for the recipient) which I will send
> later to him, so he will be able to decrypt the message. A bit
> complicated but possible, I think!? ^^

That doesn't make any sense. If you use symmetric encryption then you=20
have to tell the recipient the passphrase you used for encryption via a=20
safe channel.

If you use a private key then you have to tell the recipient the private=20
key and the passphrase you used to protect the private key again via a=20
safe channel. Of course, you could choose to leave the private key=20
unprotected.

In both cases you have to share a secret with the recipient via a safe=20
channel. So, where do you see the advantage of using a private key? A=20
possible reason would be re-use of the private key. But then you could=20
as well re-use the passphrase.


Regards,
Ingo

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