This article introduces the concept of “3TOFU” — a harm-reduction process when downloading software that cannot be verified cryptographically.
⚠ NOTE: This article is about harm reduction.
It is dangerous to download and run binaries (or code) whose authenticity you cannot verify (using a cryptographic signature from a key stored offline). However, sometimes we cannot avoid it. If you’re going to proceed with running untrusted code, then following the steps outlined in this guide may reduce your risk.
TOFU
TOFU stands for Trust On First Use. It’s a (often abused) concept of downloading a person or org’s signing key and just blindly trusting it (instead of verifying it).
3TOFU
3TOFU is a process where a user downloads something three times at three different locations. If-and-only-if all three downloads are identical, then you trust it.
Why 3TOFU?
The EFF’s Deep Crack proved DES to be insecure and pushed a switch to 3DES.
During the Crypto Wars of the 1990s, it was illegal to export cryptography from the United States. In 1996, after intense public pressure and legal challenges, the government officially permitted export with the 56-bit DES cipher — which was a known-vulnerable cipher.
This article is a part 3/3 of a series describing how to setup an Ephemeral Firefox session as a Site-Specific Browser. The ultimate goal is to be able to have a self-destructing browsing session that can only access a single company’s services, such as Google or Facebook.
Part 1/3: Ephemeral Firefox in Ubuntu Part 2/3: Ephemeral Firefox with Extensions Part 3/3: Ephemeral Firefox as a Site-Specific Browser
After setting up the Site-Specific Ephemeral Firefox Browser, you can then blacklist services designated to your Site-Specific browser(s) (such as Google or Facebook) from your main browser. This significantly improves your ability to browse the internet without your activity being tracked by these companies — leaving your sensitive data vulnerable to being stolen by hackers.
Michael Altfield
Hi, I’m Michael Altfield. I write articles about opsec, privacy, and devops ➡
I recently posted about how to create a sandboxed firefox profile to compartmentalize (and shred) your firefox browsing history in an Ephemeral Firefox session. But so far I’ve only covered how to create a simple vanilla firefox profile. What if you want your Ephemeral Firefox to include a few basic extensions?
This post will cover how to add extensions to your Ephemeral Firefox profile.
Part 1/3: Ephemeral Firefox in Ubuntu Part 2/3: Ephemeral Firefox with Extensions Part 3/3: Ephemeral Firefox as a Site-Specific Browser Michael Altfield
Hi, I’m Michael Altfield. I write articles about opsec, privacy, and devops ➡
This post will describe what hardware to buy & how to configure it so that you have 2 wireless networks in your house: One that seamlessly forces all of the traffic on that network through a VPN–and one that connects to the Internet normally . When finished, the internet activity for any device connected to the first network will be entirely encrypted so that the ISP cannot see which websites are visited*, what software you use, and what information you send & receive on the internet.
* Assuming your config doesn’t leak DNS; see improvements section
Update 2017-08-25: Added “kill switch” firewall rule that prevents LAN traffic from escaping to the ISP unless it passed through the VPN’s vtun0 interface first. Following this change, if the VPN connection is down, the internet will not be accessible (as desired) over the ‘home’ wifi network (without this, the router bypasses the VPN by sending the packets straight to the ISP–giving a false sense of privacy).
Your browser aggrigates a *lot* of data about your computer, and it won’t hesitate to provide all of this data to a nosy web site. In fact, if a website requests a large dataset of your computer’s configuration, concatinates it together, and passes it through a hash function, the resulting hash can be farily unique.
This procedure can be done (and is done) on seperate websites to track users and their activity across multiple websites. If the same procedure [get data, concatenate, hash()] produces the same hash value when done on 2 seperate websites, the website can be fairly certain that you’re the same user. This technique for tracking users is known as Browser Fingerprinting.
Just to get an idea of how effective this is, here’s an excerpt from the above-linked article:
[The EFF] found that, over their study of around 1 million visits to their study website, 83.6% of the browsers seen had a unique fingerprint; among those with Flash or Java enabled, 94.2%. This does not include cookies!
You can test the uniqueness of your browser’s “fingerprint” using this handy EFF tool.
