This presentation was given at the University of Washington on January 18, 2016 and is publicly available on Google Docs. If I get worthwhile feedback, I will update the presentation. Like the rest of my blog, the presentation and images are CC-BY. I will include the images at the end of this article (pending).
01 of 31, title
This quote is from Edward Snowden, from October 2015, via Micah Lee’s interview from The Intercept.
This talk is for everyone. You don’t need to be an activist, journalist or a lawyer to have to need Tor. Even the most boring, uninteresting person in the world should be defending their rights to privacy and freedom of expression by using Tor.
The aim of this ~30 minute talk (plus Q/A) is to help make understanding of Tor and Onion Services easier. It is not a highly technical talk, but it is technical. I expect that users that wish to gain knowledge of how technical systems work, to take advantage of them, must learn technical material.
The talk discusses how the Tor network works to protect your privacy by juxtaposing plain HTTP, HTTPS, and also mainstream VPN technology. I will be discussing why the advertising industry is an even greater threat than even the NSA (to most people) and why VPNs just can’t cut it. Lastly, I will discuss how Onion services is a paradigm shift from standard client-server communications, how it works to protect your privacy, and why Onion services is an important application for service providers concerned about uptime and security.
02 of 31, sources
Most of the content of my talk is sourced from these two blog posts of mine.
https://yawnbox.com/index.php/2016/01/04/use-tor-browser-or-harden-firefox-for-privacy/
https://yawnbox.com/index.php/2015/10/25/comparing-http-https-vpn-and-tor-with-snail-mail-metaphors/
03 of 31, http / postcard
As you probably know, sending a postcard in the mail allows anyone that handles the postcard to view and retain both the metadata (activity records of who, when, and where) and content. Plain HTTP is no different, except digital content is much easier and cheaper to collect and store.
04 of 31, http / postcard
This clear-text content and metadata is represented here in purple. It is completely defenseless in transit. Anyone connecting to, for example, bbc.co.uk allows anyone between you and the BBC service provider to view, retain, and maybe even change the metadata or content in transit.
05 of 31, https / letter
Sending a letter in the mail has one layer of protection, the envelope, and is analogous to HTTPS. The NSA considers HTTPS encrypted traffic “clear text” because metadata is still clear text, and a lot can be learned about the content of HTTPS encrypted traffic through automated analysis.
06 of 31, https / letter
HTTPS protected content is represented here by a red circle protecting the purple content at the center. Connecting to yandex.ru, even though encrypted with (presumably) high-grade HTTPS, still divulges a great deal of information (metadata) to anyone handling your traffic as it traverses the Internet.
07 of 31, virtual private network… 1-hop proxy
VPNs are largely one-hop proxies. It is possible to set up your own multi-hop VPN proxies, just like you can set up your own private Tor network if you have the time, expertise, and money. But mainstream VPN providers, to keep the time it takes to send your traffic back and forth across the Internet, only use one proxy. In other words, VPN providers, to keep most people happy, focus on speed rather than privacy.
Purchasing a private PO BOX or mailbox from a UPS store is analogous to purchasing VPN service from a provider. You are paying someone to “one-hop” proxy your mail so that the destination of your mail cannot know your real home address.
08 of 31, vpn / postcard
In this example, you are using the Ipredator (ipredator.se) VPN service provider in order to connect to amazon.com. Amazon still does not provide transport security and thus privacy for users of their service when searching for products to buy. Your Amazon-bound Internet traffic has one layer of protection, the orange circle, only up until the VPN service provider. Once your Amazon-bound traffic leaves the VPN provider (the one-and-only one-hop proxy), Amazon searches are as naked as postcards.
If network adversaries observing the Amazon searches somewhere between the VPN provider and Amazon may also be able to determine who is doing the searches based on the content of the Internet traffic, because these Amazon searches are just like sending postcards in the mail. Said adversaries can view, record, and change any of the metadata or content.
09 of 31, vpn / letter
In this example, when connecting with HTTPS to Wikipedia.org and using the Ipredator VPN service, the data (purple) is protected by by a layer of HTTPS (red) and also the VPN (orange). Once the Wikipedia-bound Internet traffic is proxied by Ipredator, it loses the VPN-encrypted (orange) layer, and your traffic’s content is still protected by Wikipedia’s HTTPS-encrypted (red) layer.
10 of 31, vpn circuits
As previously discussed, VPNs are one-hop proxies. The “circuit” that is made between you and the VPN service provider is static — the operator and the IP subnet never changes. The “IP subnet” of the VPN provider determines the IP address that your Internet traffic uses and is constrained by the pool of available IP addresses the VPN provider has available.
The one-hop proxy / circuit design is purposeful in order to maintain minimal latency (the time it takes for your traffic to reach the VPN provider), and to maximize bandwidth (how much you can download or upload per second).
11 of 31, the onion router… 3-hop proxy
Tor is more complex and can generally be described as a three-hop proxy. It would be like purchasing PO BOX services from three different, globally diverse mail proxy service providers, and each of those providers automatically works with each other to relay your mail to maximally protect your home address and maybe even your identity.
When sending mail communications, the first mail proxy knows who you are and also knows who the second mail proxy is. The second mail proxy only knows who the first and third mail proxies are. By the time your mail gets to the third and final mail proxy, your home address is not in any of the metadata that is destined for the recipient. And unless you disclosed your identity in the content of your communications, the recipient cannot know your identity, either.
12 of 31, tor / postcard
1. Tor encrypts your Ebay-destined traffic in three layers before leaving your computer.
2. Green circle: the Tor encrypted traffic from your computer to the Tor guard relay. The guard relay removes this first layer of encryption.
3. Yellow circle: the Tor encrypted traffic from the guard relay to the middle relay. The middle relay removes the second layer of encryption.
4. Orange circle: the Tor encrypted traffic from the middle relay to the exit relay. The exit relay removes the last layer of encryption and sends your traffic on to Ebay. Naked.
Connecting to ebay.com over Tor and searching Ebay does not disclose your IP address or your identity unless you log in to Ebay. Logging in to Ebay would disclose your identity to Ebay and thus may disclose the probability of your physical location if you gave Ebay or PayPal your home address as a shipping destination. If you browse Ebay without logging in but search for things that could allow an adversary to identify who is doing the searches, then you may disclose your identity that way, too.
If network adversaries observing the Ebay searches somewhere between the Tor exit relay and Ebay may also be able to determine who is doing the searches based on the content of the Internet traffic, because these Ebay searches are just like sending postcards in the mail. Said adversaries can view, record, and change any of the metadata or content.
13 of 31, tor / letter
1. Tor encrypts your Twitter-destined traffic in three layers before leaving your computer. Then, because Twitter requires that you use HTTPS to connect to Twitter, the first connection to Twitter establishes HTTPS (red), and then all of your Twitter-bound traffic will be encrypted in four layers of encryption.
2. Green circle: the Tor encrypted traffic from your computer to the Tor guard relay. The guard relay removes this first layer of encryption.
3. Yellow circle: the Tor encrypted traffic from the guard relay to the middle relay. The middle relay removes the second layer of encryption.
4. Orange circle: the Tor encrypted traffic from the middle relay to the exit relay. The exit relay removes the last layer of encryption and sends your traffic on to Twitter. Because of HTTPS, the content of your Twitter-bound traffic is still protected.
Connecting to twitter.com over Tor and searching Twitter does not disclose your IP address or your identity unless you log in to Twitter. Logging in to Twitter would disclose your identity to Twitter. If you browse Twitter without logging in but search for things that could allow an adversary to identify who is doing the searches, then you may disclose your identity that way, too.
Network adversaries observing Twitter searches somewhere between the Tor exit relay and Twitter can not determine who is doing the searches, because these searches are like letters in the mail. Said adversaries can still view and record any of the metadata but not the content.
14 of 31, tor circuits
Unlike VPN circuits, Tor circuits are generated randomly by your local Tor client. Tor circuits are required to have significant international hops in order to minimize the threat of surveillance or attack from a potentially malicious volunteer operator operating multiple relays in different IP subnets. In addition to Tor circuit randomness when starting Tor Browser, circuits are automatically and randomly changed every 10 minutes.
The downsides of using Tor is that, due to the required use of three geographically diverse hops, each of which likely has limited bandwidth, both high-latency and low-bandwidth experiences are high probabilities.
This is more of a positive than a negative, especially versus a typical VPN, but a Tor user must trust a random selection of roughly 2,000 guard relay operators and roughly 1,000 exit relay operators per circuit. Further, the Tor specification requires that relays belonging to the same operator cannot be used within the same circuit, presuming any given volunteer operator is not using different IP subnets.
15 of 31, tor circuits
By now, it should be clear that the number of relay operators is critical to the success of Tor and its users. Similarly, because all Tor traffic generally looks the same, it is similarly critical for the success of the Tor network for there to be a high number of users and services (Onion services).
Most purchasable Internet security services are built using a controlled set of infrastructure. This is a form of centralization. Tor is powerful exclusively because of the decentralized nature of the Tor network and the requirements of the Tor protocol. No other centralized security service can come close to having all of the security and privacy properties as Tor.
16 of 31, ads vs. nsa
We know that there are two active and constant threats to the Internet and thus its users: governments with intelligence agencies that are bent on the presumption that mass surveillance is valuable, and advertising agencies that are bent on collecting as much information about people as possible in order to sell them products. It just so happens that intelligence agencies are leveraging the work of advertising agencies because of their already deep integration into the large majority of the public Internet. Thus, the “biggest threat” to any Internet user is being attacked by advertising agencies.
However, we know that the NSA and FVEY (Five Eyes) focuses on traffic analysis leaving the Tor network, so it is highly probable that the same focus occurs for IP subnets associated with VPN service providers.
https://medium.com/message/the-hypocrisy-of-the-internet-journalist-587d33f6279e
https://www.eff.org/deeplinks/2013/12/nsa-turns-cookies-and-more-surveillance-beacons
17 of 31, vpn behavior
18 of 31, vpn behavior
These are examples of two connections to two random Internet services via a one-hop proxy in Sweden. It should be quite obvious how simple this is and how trivial it would be for a global adversary to track low-latency, one-hop proxy connections.
19 of 31, vpn behavior
VPN services might feel safe. Especially when you pull out your credit card, you expect to get what you think you’re buying. But its largely false if your goal is to defend personal privacy. VPNs are still really powerful for getting around censorship, sometimes. VPNs are also still really powerful for file sharing. But both advertising agencies and intelligence agencies are not slowed by technologies that are trivial to undermine with automatic network and data analysis.
Also important to understand is that when you hire one corporate entity to safeguard your privacy, you create one target for an adversary to legally or technically attack. Nobody can assure that VPN services do not maintain connection logs; we know that they are required to maintain payment logs, and we know that some service providers have handed over connection information while also advertising that they do not store connection information.
20 of 31, tor behavior
21 of 31, tor behavior
These examples of two Tor circuits demonstrates why adding complexity to network connections is valuable, especially compared to standard options (HTTP, HTTPS, or VPN).
22 of 31, tor behavior
I included this slide again to further stress the importance of diversity of the Tor network.
23 of 31, onion services
Common client-server connections entails you making a request to a server, to see if that server is available, and to request digital resources if the server is available. This is done by communicating directly with the server. Onion services do not work this way.
Onion services, like the ProPublica Onion site, is like a permanent Tor user that is constantly connected to the Tor network. You, the client, and ProPublica, the server both inform the Tor network of your hidden identities. The only difference is that you, the client, makes an anonymous request to the Tor network to ask if the ProPublica server is available. The Tor network, automatically and anonymously, connects the two of you through a random rendezvous point inside the Tor network. You never actually talk directly to the ProPublica Onion site, and you both have your own three-hops to protect your IP address. Since none of this traffic ever leaves the Tor network, Onion services are not vulnerable to standard forms of passive Internet surveillance.
24 of 31, onion services
In addition to being free from passive Internet surveillance, Onion services have significant security properties.
It is important for user-focused security to be default, such as high-grade HTTPS. It is also important to empower users by offering a diversity of security properties. It is important to remember that it is impossible for any one organization to fully grasp each personalized threat model for every one of their users.
Aside from the obvious user-focused security benefits of providing Onion services, there are obvious organization-focused security benefits. For example, many Fortune 1000, 500, or 100 companies commonly have website outages because of problems with DNS, BGP, or their CA. Providing Onion services helps mitigate losing access to Web resources because of these failure points.
25 of 31, onion services
The quote on slide 24 is from Roger Dingeldine as stated in his 32C3 talk, “Tor Onion Services: More Useful Than You Think”. It is a very informative talk and covers deeper issues, problems, and opportunities for the future of Onion services.
https://media.ccc.de/v/32c3-7322-tor_onion_services_more_useful_than_you_think
Every “State of the Onion” presentation is worth watching and would be an excellent primer into understanding the nature of Tor and the quality of the people behind it.
https://media.ccc.de/v/32c3-7307-state_of_the_onion
26 of 31, onion services behavior
This example of a client accessing an Onion service demonstrates the complexity and importance of Onion services. Because both the client and the server makes independent Tor circuits, both maintain anonymity while also providing end-to-end encryption.
27 of 31, onion services hosting
If you are interested in learning about or advocating for the use of Onion services, these are some useful resources.
https://help.riseup.net/en/security/network-security/tor/onionservices-best-practices
https://storify.com/AlecMuffett/tor-tips
https://www.facebook.com/notes/alec-muffett/how-to-get-a-company-or-organisation-to-implement-an-onion-site-ie-a-tor-hidden-/10153762090530962
28 of 31, tor browser
If you are brand new to Tor, or generally need assistance with using a personal computer, these step-by-step guides are perfect for Tor Browser installation and basic use.
https://ssd.eff.org/en/module/how-use-tor-windows
https://ssd.eff.org/en/module/how-use-tor-mac-os-x
29 of 31, tor browser
Tor Browser, when juxtaposed to normal Web browsers, has significant advantages when the goal is to minimize identity exposure and the effects of Web tracking. Browser plug-ins cannot accomplish these privacy-focused goals, and many of these problems are identity-divulging browser features that advertising agencies always exploit.
30 of 31, tor applications
This list is a list of Tor related software applications for different platforms. It is not an exhaustive list, and in my talk I briefly described the purpose of each one.
31 of 31, questions?
If you use a version of this presentation, be sure to leave ample time for questions!
Focus Determines Reality 
