Author: dbkr
Date: 2006-07-12 17:29:28 +0000 (Wed, 12 Jul 2006)
New Revision: 9580
Modified:
trunk/apps/Freemail/docs/spec/spec.tex
Log:
More work on spec doc.
Modified: trunk/apps/Freemail/docs/spec/spec.tex
===================================================================
--- trunk/apps/Freemail/docs/spec/spec.tex 2006-07-12 17:09:01 UTC (rev
9579)
+++ trunk/apps/Freemail/docs/spec/spec.tex 2006-07-12 17:29:28 UTC (rev
9580)
@@ -45,6 +45,7 @@
\item messagetype - This should be 'rts', to indicate that this message is an
RTS.
\item to - The Freenet URI that appears encoded in Bob's Freemail address.
This is necessary in order to prevent surreptitious forwarding to support the
enryption explained later.
\item mailsite - Alice's mailsite URI
+\item ctsssk - A randomly generated KSK that Bob should insert to once he has
recieved Alice's RTS message in order to acknoweldge that he is ready to
recieve messages. This should be randomly generated and un-guessable so that
only Bob knows which key to insert to.
\end{itemize}
Following the last data item, there are two carriage-return-line-feeds,
followed by Alice's signature. This is the SHA-256 hash of the message RSA
encrypted with Alice's private key, included as raw bytes. The resulting
message is then RSA encrypted with Bob's public key. If the resulting message
is longer than a single RSA block, the message is encoded in chunks equal to
the maximum block size and the ciphertext blocks are concatenated to form the
final message.
@@ -53,8 +54,23 @@
This RTS message is then inserted to Freenet. The URI which it inserted to is
derived from the 'rtskey' value in Bob's mailsite. The string, 'KSK@' is
prepended a hyphen, the current date in the standard date format (see section
\ref{standard_date}) is appended, followed by another hypen and a slot number.
The slot number should be set to the lowest integer starting from 1, that does
not cause a collision.
+Alice then regularly polls the KSK she put as the value of 'ctsssk' until she
retrives a CTS message (see next section).
+
\subsection{CTS Messages}
+When Bob recieves an RTS message from Alice, he decrypts the message using his
RSA private key. He then retrives the mailsite advertised in the RTS message.
Having done this, he reads the signature on the end and decrypts the signature
with the public key he just retrieved from the mailsite. He then calculates a
SHA-256 checksum of the message and checks that his checksum is identical to
the one he has decrypted. If it is not, he must discard the message. This
ensures that the message is really from Alice. He must then read the 'to' field
and ensure that its value is identical to his mailsite URI. If it is not, he
must discard the message. This ensures that he is the intended recipient of the
message.
+Bob then records the value of the 'commssk' key so that he can poll this SSK
for messages periodicaly. Before doing so, he creates another propfile with the
following values:
+
+\begin{itemize}
+\item messagetype - This should be 'cts' to indicate that this is a
clear-to-send message
+\end{itemize}
+
+Bob inserts this file to the value of the 'ctsssk' key in the RTS message.
+
+This message contains no valuable information and so does not need to be
encrypted. It also does not need to be signed since only Alice and Bob know the
KSK to which it must be inserted, so Alice knows that Bob must have inserted
the message. The KSK that Bob inserts this message to tells Alice what RTS it
relates to if there is any ambiguity.
+
+TODO: Polling of commssks.
+
\section{Message Exchange}
\subsection{The Messages}
