Hal <hfinney@shell.portal.com>:

Let me get straight where we are. Rishab's concrete proposal was not an implementation, but rather a set of requirements. There was no suggestion about any specific algorithms that would meet those requirements, right? The question is whether any such algorithm could exist.

Right.

It is hard for me to see how this could possibly work. The message receiver sends this "selection key" to the intermediary, and that somehow pulls out the saved message, but in a form such that the intermediary doesn't recognize it. And the intermediary himself can't tell exactly which message is produced. But it is nevertheless exactly the message which was meant for this particular receiver.

It need not be the same information - i.e. if the encryption process adds enough noise to the message, the extraction process might by lossy, without any total loss for the receiver. This may be possible particularly if Fourier-style transforms are used, as the "selection key" could pick up less "frequencies" of a message than are stored at the intermediary.

The thing is, the receiver does not have much more information than the intermediary.

The same could be said of a private/public key pair. What is crucial is the association between the keys. This said, while I can imagine separate systems for the intermediary loosing correlation between incoming and outgoing messages (eg - it's _really_ tough, without fancy pattern recognition, to associate a JPEG with the original), and for generating three associated keys (secret splitting? something to do with Brands' blind signatures?), I really can't imagine a way of putting it all together. Someone will have to be inspired, as Diffie was... ----------------------------------------------------------------------------- For Electric Dreams subscriptions and back issues, send a mail to rishab@arbornet.org with 'get help' as the message Subject. Rishab Aiyer Ghosh rishab@dxm.ernet.in rishab@arbornet.org Vox +91 11 6853410 Voxmail 3760335 H 34C Saket, New Delhi 110017, INDIA