From: hughes@ah.com (Eric Hughes)
Date: Tue, 5 Oct 93 13:19:09 PDT
To: cypherpunks@toad.com
Subject: Crypto Idea; Multi-Part Sigs
In-Reply-To: <9310051612.AA03681@jobe.shell.portal.com.shell.portal.com>
Message-ID: <9310052004.AA13975@ah.com>
MIME-Version: 1.0
Content-Type: text/plain


>You can't have it that each of three individuals can decrypt messages
>sent to a key, while they all have to cooperate to sign messages.

You can, but the key can't be a regular RSA key.

>Generally speaking, decryption and signing are identical in the RSA
>cryptosystem.

That's right, don't use RSA as such.

Choose two RSA keys.  Make one as Hal describes for signing.  Use the
other one for receiving.  The public key in this system is a pair of
public RSA keys.  You break symmetry, and lose automatic PGP support,
but it seems to have the characteristics required.

Eric