Courrier électronique | EPFL Graph Search

vignette|alt=@|L’arobase, caractère indispensable de l’adresse électronique. Un courrier électronique, également nommé courriel, mel ou e-mail (de l'anglais, prononcé , raccourci en mail), est un message écrit, envoyé électroniquement via un réseau informatique. On appelle messagerie électronique l'ensemble du système qui permet la transmission des courriels. Elle respecte des règles normalisées afin d'autoriser le dépôt de courriels dans la boîte aux lettres électronique d’un destinataire choisi par l’émetteur. Pour émettre ou recevoir des messages par courrier électronique, il faut disposer d’une adresse électronique et d'un client de messagerie (ou d’une messagerie web permettant l'accès aux messages via un navigateur web). L’acheminement des courriels, qui peuvent contenir des documents, est régi par diverses normes concernant aussi bien le routage que le contenu. Toutefois, comme le destinataire ne reçoit pas une copie conforme de l’écran de l’expéditeur, il est d'usage de res

AntispamLab - A Tool for Realistic Evaluation of Email Spam Filters

Luis Hernandez, Jean-Yves Le Boudec, Raphaël Naefen, Slavisa Sarafijanovic

The existing tools for testing spam filters evaluate a filter instance by simply feeding it with a stream of emails, possibly also providing a feedback to the filter about the correctness of the detection. In such a scenario the evaluated filter is disconnected from the network of email servers, filters, and users, which makes the approach inappropriate for testing many of the filters that exploit some of the information about spam bulkiness, users' actions and social relations among the users. Corresponding evaluation results might be wrong, because the information that is normally used by the filter is missing, incomplete or inappropriate. In this paper we present a tool for testing spam filters in a very realistic scenario. Our tool consists of a set of Python scripts for unix/linux environment. The tool takes as inputs the filter to be tested and an affordable set of interconnected machines (e.g., PlanetLab machines, or locally created virtual machines). When started from a central place, the tool uses the provided machines to build a network of real email servers, installs instances of the filter, deploys and runs simulated email users and spammers, and computes the detection results statistic. Email servers are implemented using Postfix, a standard linux email server. Only per-email-server filters are currently supported, whereas per-email-client filters testing would require additional tool development. The size of the created emailing network is constrained only by the number of available PlanetLab or virtual machines. The run time is much shorter then the simulated system time, due to a time scaling mechanism. Testing a new filter is as simple as installing one copy of it in a real emailing network, which unifies the jobs of a new filter development, testing and prototyping. As a usage example, we test the SpamAssassin filter.

2007

Analyzing and Protecting Communication Metadata

Ludovic Barman

Most communication systems (e.g., e-mails, instant messengers, VPNs) use encryption to prevent third parties from learning sensitive information.However, encrypted communications protect the contents but often leak metadata: the amount of data sent and the time it was sent, the way the data should be decrypted, the identity of the sender and the recipient.These metadata are a pervasive threat to privacy: They enable a variety of attacks that range from recovering plaintext contents from encrypted communications to inferring communicating parties.Our goal in this thesis is two-fold: First, to raise awareness about this problem by demonstrating attacks that threaten user privacy; and second, to propose novel solutions that reduce the metadata leakage and maintain acceptable usability and costs.To achieve the first goal, we present the first work that performs an in-depth analysis of the communications of wearable devices under the lens of traffic analysis.We demonstrate that the metadata of Bluetooth communications of wearable devices (smartwatches, fitness trackers, and blood-pressure monitors) leak sensitive information to a passive observer, despite the use of encryption.By design, these devices handle fine-grained and long-term, personal, medical and lifestyle-related data from their users.Our work highlights the need to rethink how sensitive data is exchanged in this setting.More generally, we confirm that metadata can pose a threat to user privacy, even in settings where traffic-analysis attacks are perhaps not an immediate threat.For the second goal, we begin by presenting a theoretical contribution that concerns ciphertext formats:Padmé, a padding function designed to reduce the metadata leakage of files and messages through their length.Padmé efficiently hides the size of objects even when they have very different sizes.Padmé is a part of PURBs, a ciphertext format that does not leak metadata, except for a small amount about the size.Then, we design systems that enable communicating while reducing metadata leakage: Anonymous Communication Networks (ACNs).ACNs protect against some metadata leakage (e.g., who is communicating and when).Traffic-analysis resistant ACNs have not seen widespread adoption yet, possibly due to their technical shortcomings.We focus on two aspects that remain unsolved: small-scale traffic-agnostic communication that achieves low latency, and large-scale asynchronous messaging that handles millions of users.We present PriFi, an ACN that provides provable traffic-analysis resistance and low-latency in the context of a local-area network.The protocol hides the source and recipient of a message by ensuring that the communication patterns of all participants are equal, even in the presence of active attacks.PriFi ensures low-latency and traffic-agnostic communication for a small set of users.We then present Rubato, an ACN for anonymous messaging that handles millions of users.Other large-scale ACNs have an important limitation: A sender and a recipient need to be online at the same time to resist intersection attacks.As participants are uncoordinated, they need to be online and to send cover traffic at all times, which is infeasible for many users.Rubato is a circuit-based mixnet that enables its users to be asynchronous; they can participate in the network according to their own schedule.Unlike previous ACNs, this enables users to participate using their mobile devices.

EPFL2021

Enforcing email addresses privacy using tokens

Roman Schlegel, Serge Vaudenay

We propose a system which allows users to monitor how their email addresses are used and how they spread over the Internet. This protects the privacy of the user and can reduce the spam phenomenon. Our solution does not require changes to the email infrastructure, can be set up by the end user on an individual basis and is compatible with any email client as long as emails are centralized on a server (e.g. an IMAP server). Nevertheless, it requires that people use email messaging quite differently

2005