academic papers

Eavesdropping on Phone Taps from Voice Assistants

The microphones on voice assistants are very sensitive, and can snoop on all sorts of data:

In Hey Alexa what did I just type? we show that when sitting up to half a meter away, a voice assistant can still hear the taps you make on your phone, even in presence of noise. Modern voice assistants have two to seven microphones, so they can do directional localisation, just as human ears do, but with greater sensitivity. We assess the risk and show that a lot more work is needed to understand the privacy implications of the always-on microphones that are increasingly infesting our work spaces and our homes.

From the paper:

Abstract: Voice assistants are now ubiquitous and listen in on our everyday lives. Ever since they became commercially available, privacy advocates worried that the data they collect can be abused: might private conversations be extracted by third parties? In this paper we show that privacy threats go beyond spoken conversations and include sensitive data typed on nearby smartphones. Using two different smartphones and a tablet we demonstrate that the attacker can extract PIN codes and text messages from recordings collected by a voice assistant located up to half a meter away. This shows that remote keyboard-inference attacks are not limited to physical keyboards but extend to virtual keyboards too. As our homes become full of always-on microphones, we need to work through the implications.

Friday Squid Blogging: Newly Identified Ichthyosaur Species Probably Ate Squid

Friday Squid Blogging: Newly Identified Ichthyosaur Species Probably Ate Squid

This is a deep-diving species that “fed on small prey items such as squid.”

Academic paper.

As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.

Read my blog posting guidelines here.

Sidebar photo of Bruce Schneier by Joe MacInnis.

Oblivious DNS-over-HTTPS

Oblivious DNS-over-HTTPS

This new protocol, called Oblivious DNS-over-HTTPS (ODoH), hides the websites you visit from your ISP.

Here’s how it works: ODoH wraps a layer of encryption around the DNS query and passes it through a proxy server, which acts as a go-between the internet user and the website they want to visit. Because the DNS query is encrypted, the proxy can’t see what’s inside, but acts as a shield to prevent the DNS resolver from seeing who sent the query to begin with.

IETF memo.

The paper:

Abstract: The Domain Name System (DNS) is the foundation of a human-usable Internet, responding to client queries for host-names with corresponding IP addresses and records. Traditional DNS is also unencrypted, and leaks user information to network operators. Recent efforts to secure DNS using DNS over TLS (DoT) and DNS over HTTPS (DoH) havebeen gaining traction, ostensibly protecting traffic and hiding content from on-lookers. However, one of the criticisms ofDoT and DoH is brought to bear by the small number of large-scale deployments (e.g., Comcast, Google, Cloudflare): DNS resolvers can associate query contents with client identities in the form of IP addresses. Oblivious DNS over HTTPS (ODoH) safeguards against this problem. In this paper we ask what it would take to make ODoH practical? We describe ODoH, a practical DNS protocol aimed at resolving this issue by both protecting the client’s content and identity. We implement and deploy the protocol, and perform measurements to show that ODoH has comparable performance to protocols like DoH and DoT which are gaining widespread adoption,while improving client privacy, making ODoH a practical privacy enhancing replacement for the usage of DNS.

Slashdot thread.

Sidebar photo of Bruce Schneier by Joe MacInnis.

Indistinguishability Obfuscation

Indistinguishability Obfuscation

Quanta magazine recently published a breathless article on indistinguishability obfuscation — calling it the “‘crown jewel’ of cryptography” — and saying that it had finally been achieved, based on a recently published paper. I want to add some caveats to the discussion.

Basically, obfuscation makes a computer program “unintelligible” by performing its functionality. Indistinguishability obfuscation is more relaxed. It just means that two different programs that perform the same functionality can’t be distinguished from each other. A good definition is in this paper.

This is a pretty amazing theoretical result, and one to be excited about. We can now do obfuscation, and we can do it using assumptions that make real-world sense. The proofs are kind of ugly, but that’s okay — it’s a start. What it means in theory is that we have a fundamental theoretical result that we can use to derive a whole bunch of other cryptographic primitives.

But — and this is a big one — this result is not even remotely close to being practical. We’re talking multiple days to perform pretty simple calculations, using massively large blocks of computer code. And this is likely to remain true for a very long time. Unless researchers increase performance by many orders of magnitude, nothing in the real world will make use of this work anytime soon.

But but, consider fully homomorphic encryption. It, too, was initially theoretically interesting and completely impractical. And now, after decades of work, it seems to be almost just-barely maybe approaching practically useful. This could very well be on the same trajectory, and perhaps in twenty to thirty years we will be celebrating this early theoretical result as the beginning of a new theory of cryptography.

On Blockchain Voting

On Blockchain Voting

Blockchain voting is a spectacularly dumb idea for a whole bunch of reasons. I have generally quoted Matt Blaze:

Why is blockchain voting a dumb idea? Glad you asked.

For starters:

  • It doesn’t solve any problems civil elections actually have.
  • It’s basically incompatible with “software independence”, considered an essential property.
  • It can make ballot secrecy difficult or impossible.

I’ve also quoted this XKCD cartoon.

But now I have this excellent paper from MIT researchers:

“Going from Bad to Worse: From Internet Voting to Blockchain Voting”
Sunoo Park, Michael Specter, Neha Narula, and Ronald L. Rivest

Abstract: Voters are understandably concerned about election security. News reports of possible election interference by foreign powers, of unauthorized voting, of voter disenfranchisement, and of technological failures call into question the integrity of elections worldwide.This article examines the suggestions that “voting over the Internet” or “voting on the blockchain” would increase election security, and finds such claims to be wanting and misleading. While current election systems are far from perfect, Internet- and blockchain-based voting would greatly increase the risk of undetectable, nation-scale election failures.Online voting may seem appealing: voting from a computer or smart phone may seem convenient and accessible. However, studies have been inconclusive, showing that online voting may have little to no effect on turnout in practice, and it may even increase disenfranchisement. More importantly: given the current state of computer security, any turnout increase derived from with Internet- or blockchain-based voting would come at the cost of losing meaningful assurance that votes have been counted as they were cast, and not undetectably altered or discarded. This state of affairs will continue as long as standard tactics such as malware, zero days, and denial-of-service attacks continue to be effective.This article analyzes and systematizes prior research on the security risks of online and electronic voting, and show that not only do these risks persist in blockchain-based voting systems, but blockchains may introduce additional problems for voting systems. Finally, we suggest questions for critically assessing security risks of new voting system proposals.

You may have heard of Voatz, which uses blockchain for voting. It’s an insecure mess. And this is my general essay on blockchain. Short summary: it’s completely useless.

Detecting Phishing Emails

Research paper: Rick Wash, “How Experts Detect Phishing Scam Emails“:

Abstract: Phishing scam emails are emails that pretend to be something they are not in order to get the recipient of the email to undertake some action they normally would not. While technical protections against phishing reduce the number of phishing emails received, they are not perfect and phishing remains one of the largest sources of security risk in technology and communication systems. To better understand the cognitive process that end users can use to identify phishing messages, I interviewed 21 IT experts about instances where they successfully identified emails as phishing in their own inboxes. IT experts naturally follow a three-stage process for identifying phishing emails. In the first stage, the email recipient tries to make sense of the email, and understand how it relates to other things in their life. As they do this, they notice discrepancies: little things that are “off” about the email. As the recipient notices more discrepancies, they feel a need for an alternative explanation for the email. At some point, some feature of the email — usually, the presence of a link requesting an action — triggers them to recognize that phishing is a possible alternative explanation. At this point, they become suspicious (stage two) and investigate the email by looking for technical details that can conclusively identify the email as phishing. Once they find such information, then they move to stage three and deal with the email by deleting it or reporting it. I discuss ways this process can fail, and implications for improving training of end users about phishing.

Determining What Video Conference Participants Are Typing from Watching Shoulder Movements

Determining What Video Conference Participants Are Typing from Watching Shoulder Movements

Accuracy isn’t great, but that it can be done at all is impressive.

Murtuza Jadiwala, a computer science professor heading the research project, said his team was able to identify the contents of texts by examining body movement of the participants. Specifically, they focused on the movement of their shoulders and arms to extrapolate the actions of their fingers as they typed.

Given the widespread use of high-resolution web cams during conference calls, Jadiwala was able to record and analyze slight pixel shifts around users’ shoulders to determine if they were moving left or right, forward or backward. He then created a software program that linked the movements to a list of commonly used words. He says the “text inference framework that uses the keystrokes detected from the video … predict[s] words that were most likely typed by the target user. We then comprehensively evaluate[d] both the keystroke/typing detection and text inference frameworks using data collected from a large number of participants.”

In a controlled setting, with specific chairs, keyboards and webcam, Jadiwala said he achieved an accuracy rate of 75 percent. However, in uncontrolled environments, accuracy dropped to only one out of every five words being correctly identified.

Other factors contribute to lower accuracy levels, he said, including whether long sleeve or short sleeve shirts were worn, and the length of a user’s hair. With long hair obstructing a clear view of the shoulders, accuracy plummeted.

Sidebar photo of Bruce Schneier by Joe MacInnis.

The Legal Risks of Security Research

The Legal Risks of Security Research

Sunoo Park and Kendra Albert have published “A Researcher’s Guide to Some Legal Risks of Security Research.”

From a summary:

Such risk extends beyond anti-hacking laws, implicating copyright law and anti-circumvention provisions (DMCA §1201), electronic privacy law (ECPA), and cryptography export controls, as well as broader legal areas such as contract and trade secret law.

Our Guide gives the most comprehensive presentation to date of this landscape of legal risks, with an eye to both legal and technical nuance. Aimed at researchers, the public, and technology lawyers alike, its aims both to provide pragmatic guidance to those navigating today’s uncertain legal landscape, and to provoke public debate towards future reform.

Comprehensive, and well worth reading.

Here’s a Twitter thread by Kendra.

Sidebar photo of Bruce Schneier by Joe MacInnis.