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diff --git a/content/posts/sybil-resistance-identity/images/succulents.jpg b/content/posts/sybil-resistance-identity/images/succulents.jpg Binary files differnew file mode 100755 index 0000000..938bffd --- /dev/null +++ b/content/posts/sybil-resistance-identity/images/succulents.jpg diff --git a/content/posts/sybil-resistance-identity/index.rst b/content/posts/sybil-resistance-identity/index.rst new file mode 100644 index 0000000..869a782 --- /dev/null +++ b/content/posts/sybil-resistance-identity/index.rst @@ -0,0 +1,192 @@ +--- +title: "Sybil Resistance and Digital Identity" +date: 2020-09-09T15:00:00+02:00 +--- + +.. raw:: html + + <figure class="header"> + <img src="images/succulents.jpg"> + <figcaption>Photo by <a href="https://unsplash.com/@timbennettcreative">Tim Bennett</a> on <a href="https://unsplash.com/">Unsplash</a></figcaption> + </figure> + + +Sybil in Cyberspace +=================== + +In informatics, the term *distributed system* is used to describe the aggregate behavior of a complex network made up of +individual computers. For decades, computer scientists to some success have been trying to figure out how exactly the +individual computers that make up such a distributed system need to be programmed for the resulting amalgamation to +behave in a predictable, maybe even a desirable way. Though seemingly simple on its surface, this problem has a +surprising depth to it that has yielded research questions for a whole field for several decades now. One particular +as-of-yet unsolved problem is resistance against so-called *sybil attacks*. Named after the 1973 book by Flora Rheta +Schreiber on dissociative identity disorder, in distributed systems a sybil attack is an attack where one computer +acts to the rest of the network as if it were multiple, independent systems. The core insight is that there cannot be +any technological way of preventing such an attack, and any practical countermeasure must be grounded in some authority +or ground truth that is external to the systems—bridging from technology to its social or political context. + +Looking around, we can see a parallel between this question ("which computer is a real computer?") and a social issue +that recently has been growing in importance: Just like computers can pretend to be other computers, they can also +pretend to be humans. As can humans. Be it within the context of election manipulation or down-to-earth astroturfing_ +the recurring issue is that in todays online communities, it is hard for an individual to tell who of their online +acquaintances are who they seem to be. Different platforms attempt different solutions to this problem, and all fail in +some way or another. Facebook employs good old snitching, turning people against each other and asking them "Do you know +this person?". Twitter is more laid-back and instead of such Stasi_ methodology simply opts to require a working mobile +phone number from its subjects, essentially short-circuiting identity verification to the phone company's check of their +subscriber's national passport. + +Trusting Crypto-Anarchist Authorities +===================================== + +Beyond these centralistic solutions to the problem, crypto-anarchists and anarcho-capitalists have been brewing some +interesting novel approaches to this issue based on *blockchain* distributed ledger technology. Distributed ledgers, +often colloquially called "blockchains", are a distributed systems design pattern that yields a system that works like +an append-only logbook. Participants with the right permissions can create new entries in this logbook, but +noone—neither the original author, nor other participants—can retroactively change a logbook entry once it has been +committed to the log. In the blockchain model, past entries are essentially written into stone. This near-perfect +immutability is the property that opens them for a number of use cases from cryptographic pseudo-currencies +[#cryptocurrency]_. + +An overview over a variety of these unconventional blockchain identity verification approaches can be found in `this +unpublished 2020 survey by Siddarth, Ivliev, Siri and Berman <https://arxiv.org/ftp/arxiv/papers/2008/2008.05300.pdf>`_. +They walk their readers through a number of different projects that try to solve the question "Is this human who they +pretend to be?" using joint socio-technological approaches. In the following few sections, you may find a short outline +of a small selection of them. The conlusion of this post will be a commentary on these approaches, and on the underlying +problem of identity in a digital world. + +.. BrightID + +In one scheme, identity is determined by "notary" computers that aggregate large amounts of information on a user's +social contacts. These computers then run an algorithm derived from the SybilGuard_, SybilLimit_ and SybilInfer_ lineage +of random-walk based algorithms. These algorithms assume that authentic social graphs are small world graphs: Everyone +knows everyone else through a friend's friend's friend. They also assume that there is an upper bound on how many +connections with authentic users an attacker can forge: Anyone who is not embedded into the graph well enough is cut +out. Disregarding the catastrophic privacy issues of storing large amounts of data on social relationships on someone +else's computer, this second assumption is where this model unfortunately breaks down. Applying common sense, it is +completely realistic for an attacker to forge a large number of social connections: This is precisely what most of +social media marketing is about! A more malicious angle on this would be to consider how in meatspace [#meatspacefn]_ +multi-level marketing schemes are successful in coaxing people to abuse their social graphs to disastrous consequences +to the well-being of themselves and others. Similar schemes would certainly be possible in cyberspace as well. + +An additional point to consider is that the upper limit SybilGuard_ and others place on the number of fake identities +one can have is simply not that strict at all. An attacker could still get away with a reasonable number of false +identities before getting caught by any such algorithm. + +.. Duniter + +In another scheme, identity is awarded to anyone who can convince several people already in the network to vouch for +them, and who is at most a few degrees removed from one of several pre-determined celebrities. Apart from again being +vulnerable to conmen and other scammers, this system has the glaring flaw of roundly refusing to recognize any person +who is not willing or able to engage with multiple of its members. Along with the system's informal requirement for +members to only vouch for people they have physically met this leads to a nonstarter in a cyberspace that grown +specifically *because* it transcends national borders and physical distance. + +.. Idena Network + +The last scheme I will outline in this post is based around a set of `Turing tests`_, that is, quizzes that are designed +to tell apart man and machine. In this system, all participants have to simultaneously undergo a Turing test once in a +fortnight. The system uses a particular type of picture classification-based Turing test and does not seem to be +designed with the blind or mentally disabled in mind with accessibility concerns nowhere to be found in the so-called +"manifesto" published by its creators. But even ignoring that, the system obviously fails at an even more basic level: +The idea that everyone takes a Turing test at the same time only works in a world without time zones. Or jobs for that +matter. Also, it assumes that an attacker cannot simply hire a small army of people someplace else to fool the system. + +.. _SybilLimit: https://www.comp.nus.edu.sg/~yuhf/yuh-sybillimit.pdf +.. _SybilGuard: http://www.math.cmu.edu/~adf/research/SybilGuard.pdf +.. _SybilInfer: https://www.princeton.edu/~pmittal/publications/sybilinfer-ndss09.pdf +.. _`Turing Tests`: https://en.wikipedia.org/wiki/Turing_test + +Identity between Cyberspace and Meatspace +========================================= + +A common thread in all of these solutions, be it the Facebook'esque Stasi_ methods or the crypto-anarchist +challenge-response utopias, is that they all approach digital identity as a question of Objective Truth™ that can +unanimously be decided at a system level—or that can be externalized to the next larger system such as the state. Alas, +the important question remains unasked: + + What *is* identity? + +Departing from all the systems outlined above, I want to make a suggestion on how we can approach this topic in a more +practical, less discriminatory [#discriminatory]_ manner. I think both using people's social connections and proxying +the decisions of external authorities such as the state are bad systems to decide who is a person and who is not. Let us +now illustrate this point a bit. Let us think about how many digital identities a human beign might have. Let us first +consider the case of n=0, someone who simply wants no business with the system at all. For simplicity, let us assume +that we have solved this issue of consent, i.e. every person who is identified by the system consents to this practice. +For n=1, the approaches outlined above all provide some approximate solution. States may not grant every human +sufficient ID (e.g. children, mentally disabled or prisoners might be left out), and the social systems might fail to +catch people who simply do not have any friends, but otherwise their approximations hold. Maybe. But what about n=2, +n=3, ...? None of these systems adequately consider cases where a human being might legitimately wish to hold multiple +identities, non-maliciously. + +Consider the case of a lesbian, conservative politician. An active social media presence is a core component of a modern +politician's carreer. At the same time, "conservative homophobe" is still well within the realm of tautology and it +would be legitimate for this politician to wish to not disclose this aspect of their private life to the world at large, +and have a separate online identity for matters related to it. For this politician, the social relationship-based +systems referenced above would either have outing them as a design feature, or they would force them to choose either of +these identities: Requiring them to choose between private life and carreer. When deferring to the state as the decider +over personhood, at least the platform's operator would know about the outrageously sensitive link between the +politician's online identities. Clearly, none of these systems are socially just. + +Let us try not to be caught up on saving the world at this point. The issue of conservative homophobia is out of the +scope of our consideration, and it is not one that anyone can solve in the near future. Least of all can true change be +forced through contracts, legislation or other rules. There is a case for legitimate uses of multiple, separate digital +identities, and we do not have a technical or political answer to it. All hope is not lost yet, though. We can easily +undo this gordian knot by acknowledging an unspoken assumption that underlies any social relationships between real +people, past the procrustean bed of computer systems or organizational structures these relationships are cast into. + + Identity is subjective. Identity arises from a relationship between people, and the same person might legitimately + have multiple identities to different people. + +Thinking beyond the straw man politician above, this is evident in more subtle ways in almost all our everyday +relationships: Some people may know me by my legal name, some by my online nickname. To some I may be a computer +scientist, to some a flatmate. None of my friends and acquaintances have ever wanted to see my passport, or asked to +take my DNA to ascertain that I am in fact a differnet human than the others they know. It would simply be exceedingly +weird for someone I know to snoop around the other people I know, trying to build a map of where these people know me +from and whether they think the same about me. Yet, this concept of a consistent, global identity is exactly what up to +now all technological solutions to the identity problem are about. + +Building Bridges +================ + +I think I can offer you one main take-aways from the discussion above. + + Focus on relationships, not identity. + +Rephrased into more actionable points, as someone designing a digital system, do the following: + +1. Allow people to chose their own identifier. Don't require them to use their real names, they may not wish to + disclose those or they may not be in a format that is useful to you (they may be too long, too short, too + ubiquituous, in foreign characters etc.). A free-form text field with a reasonable length limit is a good + approach here. +2. Do not use credit cards or phone numbers to identify people. There are many people who do not have either, and + scammers can simply buy this data in bulk on the darknet. +3. Allow people to create multiple accounts [#accountswitchopsec]_, and acknowledge the role of social relationships in + your interaction features. People have very legitimate reasons to separate areas of their lifes, and it is not for + you or your computer to decide who is who to whom. If your thing requires a global search function, re-consider the + data protection aspects of your system. If you want to encourage social functions in the face of bots and trolls, + make it easy for people to share their identities out-of-band, such as through a QR code or a copy-and-pasteable + short link. + +While change of perspective comes with its share of user experience challenges, but also with a promise for a more +human, more dignified online experience. Perhaps we can find a way to adapt cyberspace to humans, instead of continuing +trying it the other way around. + +.. _astroturfing: https://en.wikipedia.org/wiki/Astroturfing +.. _Stasi: https://en.wikipedia.org/wiki/Stasi + +.. [#cryptocurrency] Pseudo-currencies in that while they provide some aspects of a regular currency such as ownership and + transactions, they lack most others. Traditional currencies are backed by states, regulated by central banks + tasked with maintaining their stability and ultimately provide accountability through law enforcement, courts and + political elections. + +.. [#discriminatory] Discriminatory as in discriminating against minorities, but also as in deciding what is and what is not. + +.. [#accountswitchopsec] This does mean that you should not actively prevent people from creating multiple accounts. It + does not necessarily entail building a proper user interface around this practice. If you do the latter, e.g. by + offering a "switch identity" button or an identiy drop-down menu on a post submission form, you can easily + encourage slip-ups that might disclose the connection between two identities, and you make it possible for + someone hacking a single login to learn about this connection as well. + +.. [#meatspacefn] Meatspace_ is where people physically are, as opposed to cyberspace + +.. _Meatspace: https://dictionary.cambridge.org/dictionary/english/meatspace |
