Zero-Knowledge Succinct Non-Interactive Argument of Knowledge (zk-SNARK) schemes have gained significant adoption in privacy-preserving applications, in decentralized systems (e.g., blockchain), and in verifiable computation due to their efficiency. However, the most efficient zk-SNARKs often rely on a one-time trusted setup to generate public parameters, often known as the ''Powers of Tau'' (PoT) string. The leakage of the secret parameter τ in the string would allow attackers to generate false proofs, compromising the soundness of all zk-SNARK systems built on it.

Modern Web3 wallets offer hybrid recovery solutions that combine multiple key recovery methods to balance security, availability, and usability. These methods include secret sharing of wallet private keys, encrypted cloud storage, and smart contract-based advanced recovery functionalities. However, such combined approaches can introduce new attack vectors that are not present in standalone recovery solutions. In this work, we propose a formal security analysis frame-work for blockchain/Web3 wallet designs with key or asset recovery functionalities. To assess whether a wallet design is secure, our framework considers several factors, including user availability and responsiveness to malicious actions, co-custodianship with external parties, the total value of assets managed by the wallet, and the reputation of the entities chosen by the user to facilitate spending or recovery functionalities. Through probabilistic model checking, our framework identifies the conditions under which a wallet design remains secure. We also include two examples of Web3 wallet designs with composite recovery mechanisms (inspired by existing designs) to demonstrate the effectiveness of our framework.

Cryptocurrency users saw a sharp increase in different types of crypto wallets in the past decade. However, the emerging multi-device wallets, even with improved security guarantees over their single-device counterparts, are yet to receive proportionate adoption. This work presents a data-driven investigation into the perceptions of users towards multi-device wallets, using a survey of 357 crypto-wallet users. Our results revealed two significant groups among our participants-Newbies and Non-newbies. Our follow-up qualitative analysis, after educating, revealed a gap between the mental model for these participants and actual security guarantees. Furthermore, we investigated preferred default settings for crypto-wallets across our participants over different key-share distribution settings of multi-device wallets-the threat model considerations affected user preferences, signifying a need for contextualizing default settings. We identified concrete, actionable design avenues for future multi-device wallet developers to improve adoption.

In this paper, we perform the first multifaceted measurement study to investigate the widespread insecure practices employed by tertiary education institutes (TEIs) around the globe when offering WPA2-Enterprise Wi-Fi services. The security of such services critically hinges on two aspects: (1) the connection configuration on the client-side; and (2) the TLS setup on the authentication servers. Weaknesses in either can leave users susceptible to credential theft. Typically, TEIs prescribe to their users either manual instructions or pre-configured profiles (e.g., eduroam CAT). For studying the security of configurations, we present a framework in which each configuration is mapped to an abstract security label drawn from a strict partially ordered set. We first used this framework to evaluate the configurations supported by the user interfaces (UIs) of mainstream operating systems (OSs), and discovered many design weaknesses. We then considered 7045 TEIs in 54 countries/regions, and collected 7275 configuration instructions from 2061 TEIs. Our analysis showed that majority of these instructions lead to insecure configurations, and nearly 86% of those TEIs can suffer from credential thefts on at least one OS. We also analyzed a large corpus of pre-configured eduroam CAT profiles and discovered several misconfiguration issues that can negatively impact security. Finally, we evaluated the TLS parameters used by authentication servers of thousands of TEIs and discovered perilous practices, such as the use of expired certificates, deprecated versions of TLS, weak signature algorithms, and suspected cases of private key reuse among TEIs. Our long list of findings have been responsibly disclosed to the relevant stakeholders, many of which have already been positively acknowledged.

Abstract The Bitcoin network has offered a new way of securely performing financial transactions over the insecure network. Nevertheless, this ability comes with the cost of storing a large (distributed) ledger, which has become unsuitable for personal devices of any kind. Although the simplified payment verification (SPV) clients can address this storage issue, a Bitcoin SPV client has to rely on other Bitcoin nodes to obtain its transaction history and the current approaches offer no privacy guarantees to the SPV clients. This work presents T 3, a trusted hardware-secured Bitcoin full client that supports efficient oblivious search/update for Bitcoin SPV clients without sacrificing the privacy of the clients. In this design, we leverage the trusted execution and attestation capabilities of a trusted execution environment (TEE) and the ability to hide access patterns of oblivious random access machine (ORAM) to protect SPV clients’ requests from potentially malicious nodes. The key novelty of T 3 lies in the optimizations introduced to conventional ORAM, tailored for expected SPV client usages. In particular, by making a natural assumption about the access patterns of SPV clients, we are able to propose a two-tree ORAM construction that overcomes the concurrency limitation associated with traditional ORAMs. We have implemented and tested our system using the current Bitcoin Unspent Transaction Output (UTXO) Set. Our experiment shows that T 3 is feasible to be deployed in practice while providing strong privacy and security guarantees to Bitcoin SPV clients.

Abstract Cryptocurrencies play a major role in the global financial ecosystem. Their presence across different geopolitical corridors, including in repressive regimes, has been one of their striking features. In this work, we leverage this feature for bootstrapping Censorship Resistant communication. We conceptualize the notion of stego-bootstrapping scheme and its security in terms of rareness and security against chosencovertext attacks. We present MoneyMorph, a provably secure stego-bootstrapping scheme using cryptocurrencies. MoneyMorph allows a censored user to interact with a decoder entity outside the censored region, through blockchain transactions as rendezvous, to obtain bootstrapping information such as a censorshipresistant proxy and its public key. Unlike the usual bootstrapping approaches (e.g., emailing) with heuristic security, if any, MoneyMorph employs public-key steganography over blockchain transactions to ensure provable cryptographic security. We design rendezvous over Bitcoin, Zcash, Monero, and Ethereum, and analyze their effectiveness in terms of available bandwidth and transaction cost. With its highly cryptographic structure, we show that Zcash provides 1148 byte bandwidth per transaction costing less than 0.01 USD as fee.

Abstract Most social platforms offer mechanisms allowing users to delete their posts, and a significant fraction of users exercise this right to be forgotten. However, ironically, users’ attempt to reduce attention to sensitive posts via deletion, in practice, attracts unwanted attention from stalkers specifically to those (deleted) posts. Thus, deletions may leave users more vulnerable to attacks on their privacy in general. Users hoping to make their posts forgotten face a “damned if I do, damned if I don’t” dilemma. Many are shifting towards ephemeral social platform like Snapchat, which will deprive us of important user-data archival. In the form of intermittent withdrawals, we present, Lethe, a novel solution to this problem of (really) forgetting the forgotten. If the next-generation social platforms are willing to give up the uninterrupted availability of non-deleted posts by a very small fraction, Lethe provides privacy to the deleted posts over long durations. In presence of Lethe, an adversarial observer becomes unsure if some posts are permanently deleted or just temporarily withdrawn by Lethe; at the same time, the adversarial observer is overwhelmed by a large number of falsely flagged undeleted posts. To demonstrate the feasibility and performance of Lethe, we analyze large-scale real data about users’ deletion over Twitter and thoroughly investigate how to choose time duration distributions for alternating between temporary withdrawals and resurrections of non-deleted posts. We find a favorable trade-off between privacy, availability and adversarial overhead in different settings for users exercising their right to delete. We show that, even against an ultimate adversary with an uninterrupted access to the entire platform, Lethe offers deletion privacy for up to 3 months from the time of deletion, while maintaining content availability as high as 95% and keeping the adversarial precision to 20%.

Mobile ad hoc networks (MANETs) have been turned into very attractive area of research in the duration of recent years, whereas security is the most challenging point that they undergo. Cryptography is an essential solution for providing security within MANETs. However, storing all keys in every node, if practically possible, is inefficient in large scale MANETs due to some limitations such as memory or process capability. This paper extends our previous idea which was a novel probabilistic key management algorithm that stores only a few randomly chosen keys instead of all ones. In this paper, several different scenarios are proposed for key selection in which they are more practical, and then, the impact of each scenario on the performance and security metrics is analyzed. Results show that the proposed scenarios can reduce the path length in addition to keeping the network highly connected.