103 lines
4.1 KiB
TeX
103 lines
4.1 KiB
TeX
\documentclass{bfh}
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\usepackage[numbers]{natbib}
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\title{Informatikseminar}
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\subtitle{Bitmessage -- Communication Without Metadata}
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\author{Christian Basler}
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\tutor{Kai Brünnler}
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\date{\today}
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\newcommand{\msg}[1]{\textit{#1}}
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\newcommand{\obj}[1]{\textbf{#1}}
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\newcommand{\node}[1]{\textbf{#1}}
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\begin{document}
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\maketitle
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\tableofcontents
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\section{Synopsis}
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TODO
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% Section basics
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\input{basics}
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\section{Protocol}
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\subsection{Nomenclature}
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There are a few terms that are easily mixed up. Here's a list of the most confusing ones:
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\listinginfo{}{message}{is sent from one node to another, i.e. to announce new objects or to initialize the network connection.}{}
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\listinginfo{}{msg}{is the object payload containing the actual message written by a user. The term 'message' is never used to describe information exchange between users in this document.}{}
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\listinginfo{}{payload}{There are two kinds of payload: message payload for message types, e.g. containing inventory vectors, and object payload, which is distributed throughout the network.}{}
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\listinginfo{}{object}{is a kind of message whose payload is distributed among all nodes. Somtimes just the payload is meant.}{}
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\subsection{Process Flow}
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The newly started node \node{A} connects to a random node \node{B} from its node registry and sends a \msg{version} message, announcing the latest supported protocol version. If \node{B} accepts the version\footnote{A version is accepted by default if it is higher or equal to a nodes latest supported version. Nodes supporting experimental protocol versions might accept older versions.}, it responds with a \msg{verack} message, followed by a \msg{version} message announcing its own latest supported protocol version. Node \node{A} then decides whether it supports \node{B}'s version and sends its \msg{verack} mesage.
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If both nodes accept the connection, they both send an \msg{addr} message containing up to 1000 of its known nodes, followed by one or more \msg{inv} messages announcing all valid objects they are aware of. They then send \msg{getobject} request for all objects still missing from their inventory.
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\msg{Getobject} requests are answered by \msg{object} messages containing the requested objects.
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If a user writes a new mail on node \node{A}, it is offered via \msg{inv} to up to eight connected nodes. They will get the object and distribute it to up to eight of their connections, and so on.
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\subsection{Messages}
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The messages and binary format are very well discribed in the Bitmessage wiki \cite{wiki:protocol}, the message description is therefore narrowed down to a description of what they do and when they're used.
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\subsubsection{version / verack}
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A \msg{version} message contains the latest protocol version supported by a node, as well as the streams it is interested in and which features it supports. If the other node accepts, it acknowledges with a \msg{verack} message. The connection is initialized when both nodes sent a \msg{verack} message.
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\subsubsection{addr}
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Contains up to 1000 known nodes with their IP addresses, ports, streams and supported features.
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\subsubsection{inv}
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One \msg{inv} message contains the hashes of up to 50000 valid objects. If your inventory is larger, several messages can be sent.
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\subsubsection{getdata}
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Can request up to 50000 objects by sending their hashes.
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\subsubsection{object}
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Contains one requested object, which might be one of:
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\listinginfo{}{getpubkey}{A request for a public key, which is needed to encrypt a message to a specific user.}{}
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\listinginfo{}{pubkey}{A public key. See \ref{subsec:addrenc} \nameref{subsec:addrenc}}{}
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\listinginfo{}{msg}{}{}
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\listinginfo{}{broadcast}{}{}
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\subsubsection{ping / pong}
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\subsection{Addresses and Encryption}
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\label{subsec:addrenc}
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\section{Issues}
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\subsection{Scalability}
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TODO
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\section{Discussion}
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TODO
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\bibliographystyle{plain}
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\bibliography{bibliography}
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\appendix
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\addcontentsline{toc}{section}{Appendix}
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\section*{Appendix}
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\renewcommand{\thesubsection}{\Alph{subsection}}
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\subsection{TODO}
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\end{document} |