[14959] in cryptography@c2.net mail archive
Re: Super-Encryption
daemon@ATHENA.MIT.EDU (Ben Laurie)
Thu Dec 18 12:00:43 2003
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Tue, 16 Dec 2003 18:44:59 +0000
From: Ben Laurie <ben@algroup.co.uk>
To: mlong@bridgetonconsulting.com
Cc: cryptography@metzdowd.com
In-Reply-To: <1071498336.3fddc460b7477@66.150.199.3>
mlong@bridgetonconsulting.com wrote:
> Quoting Ben Laurie <ben@algroup.co.uk>:
>
>
>>I don't see any value added by cipher1 - what's the point?
>
>
> The message is encrypted, i.e, cipher1, then cipher1 is encrypted yeilding
> cipher2.
>
> Since symmetric_key1 of cipher1 is RSA_Encrypt(sender's private key), access
> to sender's public key can decrypt cipher1(must be *this* sender).
>
> Since symmetric_key2 of cipher2 is RSA_Encrypt(receiver's public key), only
> the receiver can decrypt cipher2.
>
> As was pointed out to me, the process of decrypting cipher2, yields an
> encrypted message, i.e., cipher1, that can forwarded on behalf of the original
> sender. This is not necessarily undesirable. However, SHA1(message) is to
> ensure that cipher1 has not be altered in transport. Therefore, the receiver
> knows three items.
> (1) The sender who originated the message.
> (2) The receiver is the intended receiver.
> (3) The message was not altered during transport.
Yes, but you could know all this from cipher2 and RSA of SHA1(message),
so I still don't see what value is added by cipher1.
Cheers,
Ben.
--
http://www.apache-ssl.org/ben.html http://www.thebunker.net/
"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff
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