Category Archives: Academics

NextGen Korea Scholars

I had the incredible opportunity to spend the end of last week in Washington DC with the CSIS NextGen Scholars program meeting the US policy makers who define the US policy towards the DPRK.

It was fascinating to see the process has been put in place for weighing the different factors that go into these decisions, and how at the same time there really is truth to the almost inconceivable notion that the best any of us can hope for is that Trump and Kim Jong Un will have a successful summit and be able to make progress based on some unexpected personal trust.

I am hopeful I was able to offer some insight into what life is like in the country, and perhaps was able to offer some sense of the value provided by engagements like PUST.

Several tweets provide a sense of who we got to meet.

Ethics of Censorship Measurement

I gave a talk this past summer at DEFCON on the ethical quandary that continues to play a role in the academic discussion of network censorship measurement. Over the course of my phd studies, there was a significant arc of time where the community yielded to caution as the issues around ethics were better understood.

These issues have not gone away, and in the intervening six months since this talk, we’ve seen new groups re-develop techniques deemed problematic by the prevailing winds of the academic community.

Watch on Youtube

Slides

Corporate Censorship

One of the most interesting lines of inquiry within the Censored Planet project at the University of Michigan is trying to pull apart the different actors involved in Internet  censorship. One of the interesting quirks is that a significant factor in why content might not be available to users is that the web publisher themselves have limited who they’ll respond to.

This relates to existing phenomenons like increased balkanization of the web, where regions and nations promote domestic services and networks, but is as much a function of where lucrative markets are and a reaction to the background of fraud and malicious online traffic.

One outcome of this research is a set of measurements looking at how and where CDNs limit access, that will be presented tomorrow at IMC.

Like many parts of the Internet, a take-away here is that attribution is hard.

Open Letter to the Cuba Internet Task Force

The following is a response to an invitation to participate in the recently formed Cuba Internet Task Force.

Task Force Representatives:
I will not be joining the Cuba Internet Task Force, or Subcommittees, because I believe the harm done by the existence of these committees outweighs any potential benefit of the recommendations that can come from them.

In recent years, Cuba has increasingly normalized Internet usage, through expansion and cost reduction of WiFi, through the advent of AirBNB as a major source of tourism revenue, and through growing traffic capacity.

In the scope of my work, I have documented the flourishing community wireless networks operating in tandem with official Internet service from ETECSA. These community efforts already address the “last mile” problem, and it is not hard to imagine the future where they are consolidated or integrated to provide Internet-to-the-home for many more Cubans.

These efforts are hindered by the perception by the Cuban government that the Internet and its associated ‘freedom’ are being forced upon them by the United States. In the wake of the creation of this task force, Cuban media has focused on the implied pressure, and private individuals in the Cuban technology sector have come under increased scrutiny.

Instead of attempting to influence the policies of another sovereign nation, I encourage us to reflect more on our internal policies. US government sanctions currently require a wide range of US-based education and reference sites from blocking Cuban traffic. Likewise, limitations preventing Cubans from connecting to US-invested undersea cables are partially responsible for the scarcity and cost of Cuban Internet connections. Reducing these sanctions can allow Cubans to become a market for US companies, and will provide additional incentives for widespread connectivity across the country.

Initial Measurements of the Cuban Street Network

Internet access in Cuba is severely constrained, due to limited availability, slow speeds, and high cost. Within this isolated environment, technology enthusiasts have constructed a disconnected but vibrant IP network that has grown organically to reach tens of thousands of households across Havana. We present the first detailed characterization of this deployment, which is known as the SNET, or Street Network. Working in collaboration with SNET operators, we describe the network’s infrastructure and map its topology, and we measure bandwidth, available services, usage patterns, and user demographics. Qualitatively, we attempt to answer why the SNET exists and what benefits it has afforded its users. We go on to discuss technical challenges the network faces, including scalability, security, and organizational issues. To our knowledge, the SNET is the largest isolated community-driven network in existence, and its structure, successes, and obstacles show fascinating contrasts and similarities to those of the Internet at large.

Talks

The Internet in Cuba: A Story of Community Resilience. Chaos Communication Congress. 2017

Publication

P Pujol, Eduardo E., Will Scott, Eric Wustrow, and J. Alex Halderman. “Initial measurements of the cuban street network.” In Proceedings of the 2017 Internet Measurement Conference, pp. 318-324. ACM, 2017. Slides

IETF 98

Last week I talked briefly about the state of open internet measurement for network anomalies at IETF 98. This was my first time attending an IETF in-person meeting, and it was very useful in getting a better understanding of how to navigate the standards process, how it’s used by others, and what value can be gained from it.

A couple highlights that I took away from the event:

There’s a concern throughout the IETF about solving the privacy leaks in existing protocols for general web access. There are three major points in the protocol that need to be addressed and are under discussion as part of this: The first is coming up with a successor to DNS that provides confidentiality. This, I think, is going to be the most challenging point. The second is coming up with a SNI equivalent that doesn’t send the requested domain in plain-text. The third is adapting the current public certificate transparency process to provide confidentiality of the specific domains issued certificates, while maintaining the accountability provided by the system.

Confidential DNS

There are two proposals with traction for encrypting DNS that I’m aware of. Neither fully solve the problem, but both provide reasonable ways forward. The first is dnscrypt, a protocol with support from entities like yandex and cloudflare. It maintains a stateless UDP protocol, and encrypts requests and responses against server and client keys. There are working client proxies for most platforms, although installation on mobile is hacky, and a set of running providers. The other alternative, which was represented at IETF and seems to be preferred by the standards community is DNS over TLS. The benefit here that there’s no new protocol, meaning less code that needs to be audited to gain confidence of the security properties for the system. There are some working servers and client proxies available for this, but the community seems more fragmented, unfortunately.

The eventual problem that isn’t yet addressed is that you still need to trust some remote party with your dns query and neither protocol changes the underlying protocol where the work of dns resolution is performed by someone chosen by the local network. Current proxies allow the client to choose who this is instead, but that doesn’t remove the trust issue, and doesn’t work well with captive portals or scale to widespread deployment. It also doesn’t prevent that third party from tracking the chain of dns requests made by the client and getting a pretty good idea about what the client is doing.

Hidden SNI

SNI, or server name identification, is a process that occurs at the beginning of an HTTPS request where the client tells the server which domain it wants to talk to. This is a critical part of the protocol, because it allows a single IP address to host HTTPS servers for multiple domains. Unfortunately, it also allows the network to detect and potentially block requests at a domain, rather than IP granularity.

Proposals for encrypting the SNI have been around for a couple years. Unfortunately, they did not get included in TLS1.3, which means that it will be a while before the next iteration of the standard and the potential to include this update.

The good news was that there seems to be continued interest in figuring out ways to protect the SNI of client requests, though no current proposal I’m aware of.

Certificate Transparency Privacy

Certificate Transparency is an addition to the HTTPS system to enforce additional accountability in to the certificate authority system. It requires authorities (CA)’s to publish a log of all certificates they issue publicly, so that third parties can audit their list and make sure they haven’t secretly mis-issued certificates. While a great feature for accountability and web security, it also opens an additional channel where the list of domains with SSL certificates can be enumerated. This includes internal or private domains that the owner would like to remain obscure.

As google and others have moved to require the CT log from all authorities through requirements on browser certificate validity, this issue is again at the fore. There’s been work on addressing this problem, including a cryptographic proposal and the IETF proposal for domain label redaction which seems to be advancing through the standards process.

There remains a ways to go to migrate to protocols which provide some protection against a malicious network, but there’s willingness and work to get there, which is at least a start.