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1. Poster: End-to-End Secure Mobile Group Messaging with Conversation Integrity and Minimal Metadata Leakage

   https://doi.org/10.1145/3243734.3278506  

   Schliep, Michael; Hopper, Nicholas (January 2018, Proceedings of the 2018 ACM SIGSAC Conference on Computer and Communications Security)

   Existing End-to-End secure messaging applications trust a single service provider to deliver messages in a consistent order to a consistent group of conversation members. We propose a protocol that removes this single point of failure by using multiple service providers, enforcing conversation integrity as long as one service provider out of N behave honestly. However, this approach could potentially increase the number of entities that learn the metadata for a conversation. In this work we discuss the challenges and provide a protocol that limits the metadata leakage to that of existing messaging applications while still providing strong conversation integrity. 

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2. A Dynamic Dyadic Systems Perspective on Interpersonal Conversation

   https://doi.org/10.1080/19312458.2023.2237404  

   Solomon, Denise Haunani; Brinberg, Miriam; Bodie, Graham; Jones, Susanne; Ram, Nilam (October 2023, Communication Methods and Measures)

   Solomon, Denise Haunani; Brinberg, Miriam; Bodie, Graham; Jones, Susanne; Ram, Nilam (Ed.)

   Conversations between people are where, among other things, stressors are amplified and attenuated, conflicts are entrenched and resolved, and goals are advanced and thwarted. What happens in dyads’ back-and-forth exchanges to produce such consequential and varied outcomes? Although numerous theories in communication and in social psychology address this question, empirical tests of these theories often operationalize conversational behavior using either discrete messages or overall features of the conversation. Dynamic systems theories and methods provide opportunities to examine the interdependency, self-stabilization, and self-organization processes that manifest in conversations over time. The dynamic dyadic systems perspective exemplified by the articles in this special issue (a) focuses inquiry on the turn-to-turn, asynchronous exchange of messages between two partners, (b) emphasizes behavioral patterns within and the structural and temporal organization of conversations, and (c) adapts techniques used in analysis of intensive longitudinal data to identify and operationalize those dynamic patterns. As an introduction to the special issue, this paper describes a dynamic dyadic systems perspective on conversation and discusses directions for future research, such as applications to humancomputer interaction, family communication patterns, health care interventions, and group deliberation. 

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3. Deniable Encrypted Messaging: User Understanding after Hands-on Social Experience

   https://doi.org/10.1145/3688459.3688479  

   Rajendran, Anamika; Yadav, Tarun Kumar; Al-Jbour, Malek; Mares_Solano, Francisco Manuel; Seamons, Kent; Reynolds, Joshua (September 2024, ACM)

   Plausible deniability in cryptography allows users to deny their participation in a particular communication or the contents of their messages, thereby ensuring privacy. Popular end-to-end encrypted messaging apps employ the Signal protocol, which incorporates message deniability. However, their current user interfaces only allow access to the blunt tool of message deletion. Denying a message requires users to claim that the counterpart in their conversation has the technical sophistication to forge a message when no usable message forgery tools are available. We evaluate a step towards bridging this gap in the form of a new transcript-editing feature implemented within the Signal app which allows each user to maintain an independent, locally-editable transcript of their conversation. We gave users hands-on experience with this app in the context of resolving a social dispute, and measured their ability to understand its implications both technically and ethically. Users find our interface intuitive and can reason about deniability, but are divided by which circumstances for which deniability is appropriate or desirable. We recommend users be given transparent access to choose when their conversations are deniable versus non-repudiable, instead of the status quo of somewhere-in-between. Our study introduces a novel approach by providing hands-on experience and evaluating its usability. This method offers insights into practical deniability implementation and lays the groundwork for future research. 

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4. Private resource allocators and their applications

   https://doi.org/10.1109/SP40000.2020.00065  

   Angel, Sebastian; Kannan, Sampath; Ratliff, Zachary (May 2020, 2020 {IEEE} Symposium on Security and Privacy, {SP} 2020)

   This paper introduces a new cryptographic primitive called a private resource allocator (PRA) that can be used to allocate resources (e.g., network bandwidth, CPUs) to a set of clients without revealing to the clients whether any other clients received resources. We give several constructions of PRAs that provide guarantees ranging from information-theoretic to differential privacy. PRAs are useful in preventing a new class of attacks that we call allocation-based side-channel attacks. These attacks can be used, for example, to break the privacy guarantees of anonymous messaging systems that were designed specifically to defend against side-channel and traffic analysis attacks. Our implementation of PRAs in Alpenhorn, which is a recent anonymous messaging system, shows that PRAs increase the network resources required to start a conversation by up to 16× (can be made as low as 4×in some cases), but add no overhead once the conversation has been established. 

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5. Are You There?: Identifying Unavailability in Mobile Messaging

   https://doi.org/10.1145/3290607.3312893  

   Jain, Pranut; Farzan, Rosta; Lee, Adam J. (May 2019, Extended Abstracts of the 2019 CHI Conference on Human Factors in Computing Systems)

   Delays in response to mobile messages can cause negative emotions in message senders and can affect an individual's social relationships. Recipients, too, feel a pressure to respond even during inopportune moments. A messaging assistant which could respond with relevant contextual information on behalf of individuals while they are unavailable might reduce the pressure to respond immediately and help put the sender at ease. By modelling attentiveness to messaging, we aim to (1) predict instances when a user is not able to attend to an incoming message within reasonable time and (2) identify what contextual factors can explain the user's attentiveness---or lack thereof---to messaging. In this work, we investigate two approaches to modelling attentiveness: a general approach in which data from a group of users is combined to form a single model for all users; and a personalized approach, in which an individual model is created for each user. Evaluating both models, we observed that on average, with just seven days of training data, the personalized model can outperform the generalized model in terms of both accuracy and F-measure for predicting inattentiveness. Further, we observed that in majority of cases, the messaging patterns identified by the attentiveness models varied widely across users. For example, the top feature in the generalized model appeared in the top five features for only 41% of the individual personalized models. 

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