564 lines
18 KiB
TeX
564 lines
18 KiB
TeX
% $Header$
|
|
% use lualatex for compilation
|
|
|
|
\documentclass[aspectratio=169,navbar=false]{beamer}
|
|
|
|
% This file is a solution template for:
|
|
|
|
% - Talk at a conference/colloquium.
|
|
% - Talk length is about 20min.
|
|
% - Style is ornate.
|
|
|
|
|
|
|
|
% Copyright 2004 by Till Tantau <tantau@users.sourceforge.net>.
|
|
%
|
|
% In principle, this file can be redistributed and/or modified under
|
|
% the terms of the GNU Public License, version 2.
|
|
%
|
|
% However, this file is supposed to be a template to be modified
|
|
% for your own needs. For this reason, if you use this file as a
|
|
% template and not specifically distribute it as part of a another
|
|
% package/program, I grant the extra permission to freely copy and
|
|
% modify this file as you see fit and even to delete this copyright
|
|
% notice.
|
|
|
|
|
|
\mode<presentation>
|
|
{
|
|
\usetheme[cd2018,noddc,darktitlepage]{tud}
|
|
\usecolortheme{tud}
|
|
% or ...
|
|
|
|
%\setbeamercovered{transparent}
|
|
% or whatever (possibly just delete it)
|
|
}
|
|
|
|
% notes on 2nd screen:
|
|
\usepackage{pgfpages}
|
|
\setbeameroption{show notes on second screen}
|
|
|
|
\usepackage[british]{babel}
|
|
% or whatever
|
|
|
|
\usepackage[backend=biber, sorting=none]{biblatex}
|
|
|
|
\usepackage{ccicons}
|
|
\usepackage{wrapfig}
|
|
|
|
\usepackage{ifluatex}
|
|
|
|
\ifluatex
|
|
\usepackage{fontspec}
|
|
%\setmainfont{TeX Gyre Pagella}
|
|
%\RequirePackage{unicode-math}
|
|
%\setmathfont{XITS Math}
|
|
%\setmainfont{Open Sans}
|
|
%\setsansfont{Open Sans}
|
|
%\setmathfont[range={it}]{Open Sans:style=Italic}
|
|
%\setmathfont[range={it}]{Open Sans}
|
|
|
|
\else
|
|
\usepackage[T1]{fontenc}
|
|
\usepackage[utf8]{inputenc}
|
|
% Or whatever. Note that the encoding and the font should match. If T1
|
|
% does not look nice, try deleting the line with the fontenc.
|
|
\fi
|
|
|
|
\title[Decentralised Hashtag Federation] % (optional, use only with long paper titles)
|
|
{Decentralised Hashtag Search and Subscription
|
|
for Federated Social Networks}
|
|
|
|
\author
|
|
{Trolli Schmittlauch}
|
|
% - Give the names in the same order as the appear in the paper.
|
|
% - Use the \inst{?} command only if the authors have different
|
|
% affiliation.
|
|
|
|
\institute[] % (optional, but mostly needed)
|
|
{
|
|
Department of Computer Science\\
|
|
Technical University Dresden
|
|
}
|
|
|
|
\date[APConf 2019] % (optional, should be abbreviation of conference name)
|
|
{ActivityPubConf 2019}
|
|
\datecity{Prague}
|
|
% - Either use conference name or its abbreviation.
|
|
% - Not really informative to the audience, more for people (including
|
|
% yourself) who are reading the slides online
|
|
|
|
%\subject{Privacy}
|
|
% This is only inserted into the PDF information catalog. Can be left
|
|
% out.
|
|
|
|
|
|
|
|
% If you have a file called "university-logo-filename.xxx", where xxx
|
|
% is a graphic format that can be processed by latex or pdflatex,
|
|
% resp., then you can add a logo as follows:
|
|
|
|
% \pgfdeclareimage[height=0.5cm]{university-logo}{university-logo-filename}
|
|
% \logo{\pgfuseimage{university-logo}}
|
|
|
|
|
|
|
|
% Delete this, if you do not want the table of contents to pop up at
|
|
% the beginning of each subsection:
|
|
%\AtBeginSubsection[]
|
|
%{
|
|
% \begin{frame}<beamer>{Outline}
|
|
% \tableofcontents[currentsection,currentsubsection]
|
|
% \end{frame}
|
|
%}
|
|
|
|
|
|
% If you wish to uncover everything in a step-wise fashion, uncomment
|
|
% the following command:
|
|
|
|
%\beamerdefaultoverlayspecification{<+->}
|
|
|
|
|
|
\begin{document}
|
|
|
|
\maketitle
|
|
|
|
\note{introduce myself:\\
|
|
known as schmittlauch on the Internet\\
|
|
student of Computer Science @ TU Dresden\\
|
|
interest in federated systems and unusual social networks\\
|
|
presenting my work on a study paper from this year}
|
|
|
|
|
|
\begin{frame}{Outline}
|
|
\tableofcontents
|
|
% You might wish to add the option [pausesections]
|
|
\end{frame}
|
|
|
|
|
|
% Structuring a talk is a difficult task and the following structure
|
|
% may not be suitable. Here are some rules that apply for this
|
|
% solution:
|
|
|
|
% - Exactly two or three sections (other than the summary).
|
|
% - At *most* three subsections per section.
|
|
% - Talk about 30s to 2min per frame. So there should be between about
|
|
% 15 and 30 frames, all told.
|
|
|
|
% - A conference audience is likely to know very little of what you
|
|
% are going to talk about. So *simplify*!
|
|
% - In a 20min talk, getting the main ideas across is hard
|
|
% enough. Leave out details, even if it means being less precise than
|
|
% you think necessary.
|
|
% - If you omit details that are vital to the proof/implementation,
|
|
% just say so once. Everybody will be happy with that.
|
|
|
|
\section{Motivation}
|
|
|
|
\begin{frame}{Welcome to ActivityPubConf!}{Motivation}
|
|
|
|
|
|
\only<1>{
|
|
\includegraphics[width=\textwidth]{figures/toot_nohashtags.png}
|
|
\note{Who has been posting about this Conference?}
|
|
}
|
|
\only<2>{
|
|
\includegraphics[width=\textwidth]{figures/toot_hashtags.png}
|
|
\note{And who used \#ActivityPubConf?}
|
|
}
|
|
\end{frame}
|
|
|
|
|
|
\subsection{Importance of \#Hashtags}
|
|
|
|
\begin{frame}{Importance of \#Hashtags}{}
|
|
|
|
Hashtags are used for marking posts about certain topics or events:
|
|
\note{mark topics of posts, make them discoverable by content. No full text search in fediverse}
|
|
\begin{columns}
|
|
\begin{column}{0.47\textwidth}
|
|
|
|
\begin{itemize}
|
|
\item<1-> \textbf{events}: \#ActivityPubConf, \#CCCamp19
|
|
\item<2-> \textbf{political topics}: \#SaveTheInternet
|
|
\item<3-> \textbf{general topics}: \#mastoadmin, \#Tusky
|
|
\item<4-> \textbf{ongoing demonstrations}: \#GeziPark, \#WomensMarch
|
|
\item<5-> \textbf{social movements}: \#MeToo
|
|
\end{itemize}
|
|
\end{column}
|
|
\begin{column}{0.5\textwidth}
|
|
\begin{overlayarea}{\textwidth}{0.6\paperheight}
|
|
\center
|
|
\only<1>{
|
|
\includegraphics[width=\textwidth]{figures/APConfLogo.png}
|
|
}
|
|
\only<2>{
|
|
\includegraphics[height=0.58\paperheight]{figures/hashtag_savetheinternet.jpg}\\
|
|
\tiny{\href{https://www.flickr.com/photos/8183946@N05/14733648892}{"Obama in the Backseat: Rally to Save the Internet"} by \href{https://www.flickr.com/photos/8183946@N05}{Free Press Pics} is licensed under \href{https://creativecommons.org/licenses/by-sa/2.0/?ref=ccsearch&atype=rich}{CC BY-SA 2.0} \ccbysa}
|
|
}
|
|
\only<3>{
|
|
\includegraphics[height=0.6\paperheight]{figures/Elephant_Friend_(Greeting).png}
|
|
}
|
|
\only<4>{
|
|
\includegraphics[width=\textwidth]{figures/hashtag_gezipark.jpg}
|
|
}
|
|
\only<5>{
|
|
\includegraphics[height=0.6\paperheight]{figures/hashtag_metoo.jpg}\\
|
|
\tiny{\href{https://www.flickr.com/photos/50612692@N04/28039368079}{"IMG\_4263"} by \href{https://www.flickr.com/photos/50612692@N04}{GGAADD} is licensed under \href{https://creativecommons.org/licenses/by-sa/2.0/?ref=ccsearch&atype=rich}{CC BY-SA 2.0} \ccbysa}
|
|
}
|
|
\end{overlayarea}
|
|
\end{column}
|
|
\end{columns}
|
|
|
|
\end{frame}
|
|
|
|
\subsection{State of Hashtags in the Fediverse}
|
|
|
|
\begin{frame}{State of Hashtags on the Fediverse}{}
|
|
{\center \Large Hashtags are used in the fediverse}
|
|
\pause
|
|
\vspace{2em}
|
|
|
|
{\large But do they behave as expected?}
|
|
\end{frame}
|
|
|
|
\begin{frame}
|
|
\begin{columns}
|
|
\begin{column}{0.5\textwidth}
|
|
\begin{figure}
|
|
\includegraphics[height=0.65\paperheight]{figures/{activitypubconf_toot.matereal.eu}.png}
|
|
\caption{\#activitypubconf on the single-user instance \textit{toot.matereal.eu}}
|
|
\end{figure}
|
|
\end{column}
|
|
|
|
\begin{column}{0.5\textwidth}
|
|
\begin{figure}
|
|
\includegraphics[height=0.65\paperheight]{figures/{activitypubconf_mastodon.social}.png}
|
|
\caption{\#activitypubconf on the large instance \textit{mastodon.social}}
|
|
\end{figure}
|
|
\end{column}
|
|
\end{columns}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}{State of Hashtags on the Fediverse}{Fragmentation}
|
|
\begin{itemize}
|
|
\item fragmented view on hashtag posts depending on user's instance
|
|
\item hashtag search only on locally known posts
|
|
\item Result: incentive to cluster on large nodes \(\Leftarrow\) centralisation
|
|
\end{itemize}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}{Reason}{Push-Federation}
|
|
\begin{columns}
|
|
\begin{column}{0.55\textwidth}
|
|
\includegraphics[height=0.6\paperheight]{figures/push_federation.pdf}
|
|
\end{column}
|
|
|
|
\begin{column}{0.45\textwidth}
|
|
\begin{itemize}
|
|
|
|
\only<1>{\item subscription to \texttt{@alice@cyber.space} by contacting instance \texttt{cyber.space}}
|
|
\only<2>{\item all future posts by alice are delivered to instances of subscribers, but \textit{not} instances without any subscriber}
|
|
\only<3>{\item other ways for posts to reach an instance:\\ boosts, thread resolution}
|
|
\end{itemize}
|
|
\end{column}
|
|
\end{columns}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Current Solutions}
|
|
\begin{itemize}
|
|
\item Mastodon PubRelay or Pleroma lite-pub relay:
|
|
\begin{itemize}
|
|
\item centralised actor relaying all incoming posts
|
|
\item single point of failure, which relay to choose?
|
|
\item relaying all incoming posts \(\Rightarrow\) huge load on small instances
|
|
\item only access to posts sent after initial subscribtion
|
|
\end{itemize}
|
|
\item Diaspora* SocialRelay
|
|
\begin{itemize}
|
|
\item similar, but allows subscribing to certain tags only
|
|
\end{itemize}
|
|
|
|
|
|
\end{itemize}
|
|
|
|
\end{frame}
|
|
|
|
|
|
|
|
|
|
\section{System Architecture}
|
|
|
|
\begin{frame}{System Architecture}{Goals}
|
|
\begin{itemize}
|
|
\item \textbf{relay \& subscribe}: instances can subscribe to all public posts of a hashtag
|
|
\item \textbf{store \& query}: instances can retrieve 1 year of history for a hashtag without subscription
|
|
\item fully decentralised, no single point of authority for all tags
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
|
|
|
|
core idea: distribute responsibility for tags among instances using a \textbf{D}istributed \textbf{H}ash \textbf{T}able, \note{distribute responsibility for posts of a hashtag = relaying \& storage}
|
|
|
|
based on Chord
|
|
|
|
\note[item]{DHT: structured P2P networks providing efficient (log N) key-value storage and lookup}
|
|
\note[item]{self-organising, no central authority}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
|
|
\begin{columns}
|
|
\begin{column}{0.4\textwidth}
|
|
\begin{itemize}
|
|
\item calculate hash value of keys and node IDs
|
|
\item place these hashes onto the same circular name space
|
|
\item each node keeps routing table of \(\log \#number\_nodes\) entries\note[item]{joining and leaving covered in paper}
|
|
\end{itemize}
|
|
\end{column}
|
|
|
|
\begin{column}{0.6\textwidth}
|
|
\includegraphics[height=0.62\paperheight]{figures/finger_table_routing_1.pdf}
|
|
\end{column}
|
|
\end{columns}
|
|
\end{frame}
|
|
|
|
\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
|
|
\begin{columns}
|
|
\begin{column}{0.55\textwidth}
|
|
\begin{itemize}
|
|
\item next nodeID \(\geq\) \texttt{hash(hashtag)} (mod keyspace size) is responsible for handling posts containing \texttt{hashtag}
|
|
\item DHT used for iterative lookup of responsible relay/ storage node
|
|
\end{itemize}
|
|
\end{column}
|
|
|
|
\begin{column}{0.45\textwidth}
|
|
\includegraphics[height=0.62\paperheight]{figures/finger_table_routing_2.pdf}
|
|
\end{column}
|
|
\end{columns}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Publishing, Relaying and Storage}{lifecycle of posts}
|
|
\begin{enumerate}
|
|
\item publishing instance looks up responsible relay instance on DHT for each included hashtag
|
|
\item publishing instance sends post to responsible relay instance
|
|
\item relay instance looks up responsible storage node on DHT
|
|
\item relay instance verifies incoming post's signature, then relays post URI (ID) to all subscribers + storage node\note[item]{only post ID relayed, but not full post content. Reasons: LDSignatures not supported everywhere, deniability \& revocation}
|
|
\item subscribing instances can now retrieve the full authenticated post from received post URI
|
|
\end{enumerate}
|
|
\note[item]{for joining and leaving the DHT see paper}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}{Publishing, Relaying and Storage}
|
|
\begin{itemize}
|
|
\item separate DHTs for relay and storage instances
|
|
\item all actions after DHT lookup supposed to be done using ActivityPub via HTTPS
|
|
\item subscription to hashtags/ querying posts is done at the responsible instance
|
|
\end{itemize}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}
|
|
\note{so far so easy. But load distribution issues}
|
|
\begin{itemize}
|
|
\item node ID determines set of hashtags handled by instance
|
|
\item problem: for security reasons, node \textbf{must not} choose their IDs freely
|
|
\item Can instances be overloaded by their assigned hashtag posts?
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Distribution of Posts per Tag}
|
|
\includegraphics[width=0.49\textwidth]{statistics/twitter_hashtags_total.png}
|
|
~
|
|
\includegraphics[width=0.49\textwidth]{statistics/geraspora_hashtags_total.png}
|
|
|
|
\note{analysis of a 1 month dump of Twitter, Geraspora (Diaspora) and Friendica posts\\
|
|
Twitter: 70\% of posts used just once\\
|
|
note the logarithmic axis!}
|
|
|
|
distribution of posts per hashtag follows a steep power law
|
|
|
|
\note{So what if a small node gets several large hashtags? => need for load balancing}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Load Balancing}{of hashtags between nodes}
|
|
\begin{itemize}
|
|
\item \textit{k-choices} algorithm by Ledlie and Seltzer
|
|
\item each node can choose from \(\kappa\) possible IDs
|
|
\item nodes have a \textbf{capacity} and choose set of active IDs according to lowest mismatch of own and neighbour node capacity
|
|
\item querying load of potential IDs before joining, periodic re-balancing
|
|
\item independent load balancing of relay and storage nodes due to independent DHTs
|
|
\note[item]{a simple simulation on the effectivity of the balancing algorithm can be found in the paper}
|
|
\end{itemize}
|
|
% for Kolloquium, add simulation result
|
|
\end{frame}
|
|
|
|
\begin{frame}{Redundancy}
|
|
\begin{columns}
|
|
\begin{column}{0.55\textwidth}
|
|
\begin{itemize}
|
|
\item store redundant copies of hashtag data at equal distances on Chord ring\note{resilience against node failure, allows data validation through cross-checking}
|
|
\item default redundancy: \(2^2 = 4\), scalable in powers of 2
|
|
\item \textbf{relay nodes}: hot standby nodes take over in overload situations (load spikes)
|
|
\item \textbf{storage nodes}: overloaded nodes can split stored posts by content hash and double redundancy set
|
|
\end{itemize}
|
|
\end{column}
|
|
|
|
\begin{column}{0.45\textwidth}
|
|
\includegraphics[width=\textwidth]{figures/redundancy_ring.pdf}
|
|
\end{column}
|
|
\end{columns}
|
|
\end{frame}
|
|
|
|
|
|
\section{Discussion}
|
|
|
|
\begin{frame}{Discussion}{I need YOUR feedback}
|
|
|
|
I want feedback from all of you, no matter whether it's from a \textit{\LARGE technical} or from a \textit{\LARGE social perspective}.
|
|
|
|
\end{frame}
|
|
|
|
\subsection{Social Considerations}
|
|
|
|
\begin{frame}{Social Considerations}
|
|
Do we even want global hashtags in the Fediverse?
|
|
|
|
\begin{itemize}
|
|
\item positive potential (conversation, coordination) vs. negative potential (spam, harrasment)
|
|
\item visibility level: public posts only, unlisted, new level necessary?
|
|
\item relaying post URI only should provide plausible deniability
|
|
\item Does this circumvent instance-blocks and is this bad?
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
|
|
\subsection{Technical Considerations}
|
|
|
|
\begin{frame}{Technical Considerations}{instance admins}
|
|
|
|
\begin{itemize}
|
|
\item intended as opt-in, domain-based push federation still better for user subscriptions
|
|
\item assumption: instances offer \(5.5\times\) the storage \& \(2.5\times\) the bandwith of own posts
|
|
\item performance: Can this be implemented efficiently enough to not DDoS popular hashtag nodes?
|
|
\begin{itemize}
|
|
\item batched retrieval of posts from same source
|
|
\item exponential backoff retries
|
|
\end{itemize}
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Technical Considerations}{integration into the ActivityPub Fediverse}
|
|
\begin{itemize}
|
|
\item This architecture is an unimplemented concept so far!
|
|
\item integration into ActivityPub ecosystem\note[item]{disclaimer: I'm new to ActivityPub and have no implementation experience}
|
|
\begin{itemize}
|
|
\item hashtags may be represented as relay actors with own in- \& outbox, addressed in cc
|
|
\item relaying to subscribers via SharedInbox
|
|
\item idea for addressing: new URI scheme that gets transparently resolved to responsible node's domain via DHT\note[item]{application proxy for transparent URI scheme resolving?}
|
|
\item signalling of error codes and redundancy factors is needed
|
|
\end{itemize}
|
|
\item DHT routing communication does not use ActivityPub
|
|
\end{itemize}
|
|
\end{frame}
|
|
|
|
\begin{frame}{Technical Considerations}{node ID assignment}
|
|
|
|
\note[item]{Let's talk about the elephant in the room of ``federated services''}
|
|
\centering
|
|
\includegraphics<1>[height=0.59\paperheight]{figures/Elephant_Friend_(Greeting).png}
|
|
\includegraphics<2,4>[height=0.59\paperheight]{figures/hist_num_single_vs.png}
|
|
|
|
\note[item]{sorry to all instance admins, but: CloudFlare behaves like a MITM/ Sybil attacker}
|
|
|
|
\only<2,4>{1st peak: Masto.host, 2nd peak: Cloudflare}
|
|
|
|
\only<3>{{\ttfamily
|
|
\(h_n =\) hash(IPv6\_addr[0,63] ++ vserver)[0,63] \\
|
|
++ hash(domain ++ vserver)[0,127] \\
|
|
++ hash(IPv6\_addr[0,63] ++ vserver)[64,127]
|
|
}
|
|
\vspace{2em}
|
|
|
|
node ID derivation}
|
|
|
|
\end{frame}
|
|
|
|
\subsection{Security Considerations}
|
|
\begin{frame}{Security Considerations}
|
|
\begin{itemize}
|
|
\item attacker shall not be able to deliberately gain responsibility for certain hashtags
|
|
\begin{itemize}
|
|
\item node ID mainly dependant on IPv6 subnet
|
|
\end{itemize}
|
|
|
|
\item attacker shall not introduce arbitrary number of nodes
|
|
\begin{itemize}
|
|
\item valid domain required for node ID derivation, assumption: domains cost money
|
|
\end{itemize}
|
|
\end{itemize}
|
|
|
|
\end{frame}
|
|
|
|
|
|
\section{Summary}
|
|
|
|
\begin{frame}{Summary}
|
|
|
|
% Keep the summary *very short*.
|
|
\begin{itemize}
|
|
\item
|
|
decentralised architecture for handling posts of the same hashtag:
|
|
\begin{itemize}
|
|
\item \alert{subscribe to hashtag} and get posts \alert{relay}ed
|
|
\item \alert{query stored posts} of a certain hashtag without subscription
|
|
\end{itemize}
|
|
\item responsibility for hashtag divided among instances using a DHT
|
|
\item architecture \alert{balances the load} between nodes and maintains \alert{redundancy}
|
|
\item several open questions before implementation
|
|
\end{itemize}
|
|
|
|
% The following outlook is optional.
|
|
%\vskip0pt plus.5fill
|
|
\end{frame}
|
|
|
|
|
|
|
|
% All of the following is optional and typically not needed.
|
|
\appendix
|
|
\section<presentation>*{\appendixname}
|
|
\subsection<presentation>*{For Further Reading}
|
|
|
|
\begin{frame}[allowframebreaks]
|
|
\frametitle{References}
|
|
|
|
|
|
|
|
%\bibliography{literature}
|
|
|
|
\end{frame}
|
|
|
|
\begin{frame}
|
|
|
|
\center\huge{Questions, comments, feedback?}
|
|
|
|
\includegraphics[height=0.4\paperheight]{figures/qr_paper.png}\\
|
|
\large\url{https://git.orlives.de/schmittlauch/paper_hashtag_federation/src/branch/master/paper_hashtag_federation.pdf}
|
|
|
|
\end{frame}
|
|
|
|
|
|
\begin{frame}
|
|
|
|
|
|
%\includegraphics[height=0.5\textheight]{figures/nomnompingu.png}\tiny\footnote{CC-BY-SA 3.0 by Elektroll}
|
|
|
|
\end{frame}
|
|
|
|
|
|
\end{document}
|