From: "Rev. Mark Grant" <mark@unicorn.com>
Date: Thu, 7 Dec 95 10:55:04 PST
To: Mark Twain Ecash Support <support@marktwain.com>
Subject: Re: Still more on the Digicash protocol
Message-ID: <Pine.3.89.9512071804.A21520-0100000@unicorn.com>
MIME-Version: 1.0
Content-Type: text/plain


On Thu, 7 Dec 1995, Mark Twain Ecash Support wrote:

> >Anyhow, the obvious solution is encryption.  Our new observation is
> >that encrypting deposits & cancellations with the mint's public key
> >is not enough to solve the problem.
> [Argument in support of claim elided... I am not conviced.]

I think he means you shouldn't use a stream cipher like RC4 that XORs the
plaintext with the generated keystream, since if you know part of the
plaintext, you can XOR those bytes with (the id you want) XOR (the id
being sent) and change the encrypted data so that the payment goes into
your account and not theirs. This is a tough, but potentially feasible
attack if you use that kind of encryption scheme. 

Is there anywhere that you could use a similar attack on SSL ?

	Mark