Re: strengthening remailer protocols

[Andrew Loewenstern <andrew_loewenstern@il.us.swissbank.com>]

Wei Dai writes:
>  How about a combination of the two?  Suppose Alice wants to
>  anonymously post a message and get replies.  She generates a
>  new RSA key, signs her post with it, and asks readers to send
>  encrypted replies to a server.  Then periodicly she sends a
>  one-time reply block to the server to retrieve the accumulated
>  replies.

I'd like to chime in and say that this is a really good idea.  Basically a  
nymserver that holds onto incoming mail until an e-mail arrives from the nym  
to retrieve it.

How would mixmaster be able to support one-time reply blocks?  If the nym's  
mailbox is larger than the mixmaster message size (pretty likely) and needs  
to be split up, then more than one reply-block is going to be required.   
Should the nym generate a big stack of reply-blocks/routing headers and send   
them in with the retrieval request?  I suppose the server could fillup as  
many mixmaster message parts as it had blocks, then append something like "15  
more messages waiting (32,082 bytes - Two More Reply Blocks Required)" and  
ship it off.

Reliability is a problem with remailers... what happens now if a remailer in  
your reply block goes out and you receive mail at your nym account?  Does it  
just disappear?  With this system you could have a simple ACK protocol to  
ensure reliable delivery of the mail.  A magic cookie would be appended to  
your retrieved mail, which the server would then hold onto (it would still  
count against your quota...).  The mail would be deleted once you sent back  
an ACK with the magic cookie.

Here is yet another good application for DigiCash.  The operator could offer  
free accounts with very small mailbox quotas, or charge for bigger accounts.  
 Message retrieval could also be charged, of course.  Another idea is that  
the sender could affix postage if they wanted their message to be appended to  
a full mailbox...

A service like this is no different from something like pobox.com, except  
that this service lets you pickup your mail through e-mail instead of POP.   
So I don't think the operator would/should incurr any more liability for what  
runs through the system than pobox.




andrew

p.s.
It would also be a cool thing, IMHO, for nym servers to bounce back an  
advertisement to everyone who sends mail to a nym....   A way to spread the  
word.