[146834] in cryptography@c2.net mail archive
Re: [Cryptography] Trapdoor symmetric key
daemon@ATHENA.MIT.EDU (ianG)
Sun Sep 8 13:37:23 2013
X-Original-To: cryptography@metzdowd.com
Date: Sun, 08 Sep 2013 20:31:13 +0300
From: ianG <iang@iang.org>
To: cryptography@metzdowd.com
In-Reply-To: <CAMm+Lwg5XHe2My04jYws_orHpZcU0eg7t5j157Gea7WhH1u7aA@mail.gmail.com>
Cc: Phillip Hallam-Baker <hallam@gmail.com>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
On 8/09/13 16:42 PM, Phillip Hallam-Baker wrote:
> Two caveats on the commentary about a symmetric key algorithm with a
> trapdoor being a public key algorithm.
>
> 1) The trapdoor need not be a good public key algorithm, it can be
> flawed in ways that would make it unsuited for use as a public key
> algorithm. For instance being able to compute the private key from the
> public or deduce the private key from multiple messages.
>
> 2) The trapdoor need not be a perfect decrypt. A trapdoor that reduced
> the search space for brute force search from 128 bits to 64 or only
> worked on some messages would be enough leverage for intercept purposes
> but make it useless as a public key system.
Thanks. This far better explains the conundrum. There is a big
difference between a conceptual public key algorithm, and one that is
actually good enough to compete with the ones we typically use.
iang
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