\documentclass{article} \usepackage{fancyheadings} \pagestyle{fancy} \lhead{Free Haven Notation \\David Molnar, Roger Dingledine} \rhead{ The Free Haven Project \\http://freehaven.net/} \begin{document} \section{Glossary of Notation} \begin{description} \item[``:''] Separator between ``who is sending" and %%@ ``what is being sent." \item[$A, B, C \dots$ :] Name of a servnet node, when on %%@ left hand side of separator ``:". \item[$A_?$ :] Subscripts indicate a servnet node's %%@ status with respect to the presence or absence of a %%@ share. At this point, this reads as ``It is not known %%@ whether $A$ has the share." Which share is ``the" share %%@ is inferred from context. \item[$A_{[ ]}$ : ] Servnet node $A$ does not have the %%@ share. \item[$A_{\Phi_i}$ : ] Servnet node $A$ has share $i$ of %%@ document $\Phi$. \item[$A_{[\Phi_i]}$ :] Servnet node $A$ does not have %%@ share $i$ of document $\Phi$, but it has a pointer to %%@ someone who might have the share. \item[$A_{\Phi_i \cdot \Phi_j}$ :] Servnet node $A$ has share $i$ of document $\Phi$, which is the buddy of share $j$ of the same document. \item[$ := $ ] Becomes known. Used in a protocol to %%@ indicate a servnet node's transition from one state %%@ regarding a share to another. For example, a node may %%@ begin in a state where it is not known if it has any %%@ shares. After being asked for a particular share, the %%@ node then either has the share or it does not. \item[$ | $ :] Used to indicate several possibilities; %%@ read as an ``Or." \item[$\rightarrow$:] ``Sends to," e.g. $A \rightarrow B$ %%@ reads as ``A sends to B." \item[$\rightarrow^{\forall A}$ :] ``Sends to all members %%@ of $A$," where $A$ is some set of servnet nodes. \item[``\{, \}''] Delimiters for payload of a message. \item[$T$ :] In payload, read as holder for ``Transaction %%@ Type." \item[$E$ :] In payload, read as holder for ``Method of %%@ Encryption." \item[$<\cdot>, $ :] Reply block for whatever is %%@ inside. Read as ``reply block A" \item[$\emptyset$ :] Nobody; message received from %%@ anonymous channel. \item[$\Phi$ :] Stands for a document. \item[$\Phi$.key :] The public key associated with a %%@ document. \item[$\Phi_i$ :] Share number $i$ of the document %%@ $\Phi$. \item[$H(\cdot)$ :] Indicates a collision-resistant one-way hash function. Used to send a description of an item without sending the entire item. \end{description} \section{Document Request} In a document request, an anonymous reader sends a %%@ message to every servnet node with a description of the %%@ document it wants and a reply block. Then every node %%@ which has shares of this document sends its shares to the reply block. $ \emptyset \rightarrow A_? : \{ T, \Phi.key, , E \} $ $\forall A_{\Phi_i} A_{\Phi_i} \rightarrow : \{ E(\Phi_i) \} $ \section{Trading} Trading takes place in four steps. In the first two steps, shares are exchanged. In the next two steps, receipts for the shares are exchanged. In a trade, we have node $A$ holding share $\Phi_i$ and node $B$ holding share $\Lambda_j$ who wish to switch. $ A_{\Phi_i} \rightarrow B_{\Lambda_j} : \{ T_{T_1}, \Phi_i, Description(\Lambda_j) \}$ $ B_{\Lambda_j} \rightarrow A_{\Phi_i} : \{ T_{T_2} ,\Lambda_j, H(\Phi_i) \}$ $A_{\Phi_i} \rightarrow B_{\Lambda_j} : \{ T_{T_3}, H(\Phi_i), H(\Lambda_j), receipt \}$ $B_{\Phi_i} \rightarrow A_{\Lambda_j, \Phi_i} : \{ T_{T_4}, H(\Phi_i), H(\Lambda_j), receipt \}$ \section{Buddy Update} When a trade occurs, each share must tell its buddy about its new location. \section{Buddy Check} Now and then, a share will consult itself, realize that some time has passed, and then attempt to verify that its buddy still exists. \end{document}