Strong metadata privacy for mobile devices and applications
type: CreativeWork
description: Smartphones have become the primary computing devices for many. Living inconspicuously in our pockets, they store our most intimate personal messages and pictures as well as sensitive corporate information and government secrets. This has already motivated widespread adoption of end-to-end encryption for mobile messaging applications, such as WhatsApp and Signal, which protect the confidentiality of messages. However, metadata, such as who has been messaging whom and when, can still be observed by platform operators, local internet providers, and other adversaries tapping into network traffic. This dissertation presents protocols and applications for mobile devices that not only protect the content of messages but also communication patterns. Anonymity networks provide metadata privacy, but the most popular ones, like Tor, remain vulnerable to traffic analysis, while strong alternatives, like Loopix, use cover traffic at the expense of higher bandwidth and latency. In this context smartphones raise two important challenges: battery constraints dictate conservative power usage and connectivity is often intermittent. In order to better understand power consumption on modern smartphones we run experiments on real hardware and find that cryptographic operations are cheap while radio transmission can be costly. In particular, popular solutions such as VPN and Tor are practical with negligible impact on the battery life. However, more secure designs using cover traffic are impractical and highlight the need for protocol design that takes energy limitations into account. The latency and bandwidth requirements of protocols with strong metadata privacy are particularly challenging when sending messages to many recipients---especially on mobile devices where users are often offline. We design Rollercoaster, a multicast scheme for mix networks which incorporates these constraints and allows better utilisation of the underlying network for sporadic group communication. This ena…
abstract: Smartphones have become the primary computing devices for many. Living inconspicuously in our pockets, they store our most intimate personal messages and pictures as well as sensitive corporate information and government secrets. This has already motivated widespread adoption of end-to-end encryption for mobile messaging applications, such as WhatsApp and Signal, which protect the confidentiality of messages. However, metadata, such as who has been messaging whom and when, can still be observed by platform operators, local internet providers, and other adversaries tapping into network traffic. This dissertation presents protocols and applications for mobile devices that not only protect the content of messages but also communication patterns. Anonymity networks provide metadata privacy, but the most popular ones, like Tor, remain vulnerable to traffic analysis, while strong alternatives, like Loopix, use cover traffic at the expense of higher bandwidth and latency. In this context smartphones raise two important challenges: battery constraints dictate conservative power usage and connectivity is often intermittent. In order to better understand power consumption on modern smartphones we run experiments on real hardware and find that cryptographic operations are cheap while radio transmission can be costly. In particular, popular solutions such as VPN and Tor are practical with negligible impact on the battery life. However, more secure designs using cover traffic are impractical and highlight the need for protocol design that takes energy limitations into account. The latency and bandwidth requirements of protocols with strong metadata privacy are particularly challenging when sending messages to many recipients---especially on mobile devices where users are often offline. We design Rollercoaster, a multicast scheme for mix networks which incorporates these constraints and allows better utilisation of the underlying network for sporadic group communication. This ena…
author: Hugenroth, Daniel
language: eng
keywords: anonymity network, metadata privacy, mobile devices, security
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c30e2243-b01a-4d5c-9a54-8876274f3024/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2023-09-29
date modified: 2026-07-22T22:24:08Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.106942