3,142 research outputs found
Systemization of Pluggable Transports for Censorship Resistance
An increasing number of countries implement Internet censorship at different
scales and for a variety of reasons. In particular, the link between the
censored client and entry point to the uncensored network is a frequent target
of censorship due to the ease with which a nation-state censor can control it.
A number of censorship resistance systems have been developed thus far to help
circumvent blocking on this link, which we refer to as link circumvention
systems (LCs). The variety and profusion of attack vectors available to a
censor has led to an arms race, leading to a dramatic speed of evolution of
LCs. Despite their inherent complexity and the breadth of work in this area,
there is no systematic way to evaluate link circumvention systems and compare
them against each other. In this paper, we (i) sketch an attack model to
comprehensively explore a censor's capabilities, (ii) present an abstract model
of a LC, a system that helps a censored client communicate with a server over
the Internet while resisting censorship, (iii) describe an evaluation stack
that underscores a layered approach to evaluate LCs, and (iv) systemize and
evaluate existing censorship resistance systems that provide link
circumvention. We highlight open challenges in the evaluation and development
of LCs and discuss possible mitigations.Comment: Content from this paper was published in Proceedings on Privacy
Enhancing Technologies (PoPETS), Volume 2016, Issue 4 (July 2016) as "SoK:
Making Sense of Censorship Resistance Systems" by Sheharbano Khattak, Tariq
Elahi, Laurent Simon, Colleen M. Swanson, Steven J. Murdoch and Ian Goldberg
(DOI 10.1515/popets-2016-0028
CYCLOSA: Decentralizing Private Web Search Through SGX-Based Browser Extensions
By regularly querying Web search engines, users (unconsciously) disclose
large amounts of their personal data as part of their search queries, among
which some might reveal sensitive information (e.g. health issues, sexual,
political or religious preferences). Several solutions exist to allow users
querying search engines while improving privacy protection. However, these
solutions suffer from a number of limitations: some are subject to user
re-identification attacks, while others lack scalability or are unable to
provide accurate results. This paper presents CYCLOSA, a secure, scalable and
accurate private Web search solution. CYCLOSA improves security by relying on
trusted execution environments (TEEs) as provided by Intel SGX. Further,
CYCLOSA proposes a novel adaptive privacy protection solution that reduces the
risk of user re- identification. CYCLOSA sends fake queries to the search
engine and dynamically adapts their count according to the sensitivity of the
user query. In addition, CYCLOSA meets scalability as it is fully
decentralized, spreading the load for distributing fake queries among other
nodes. Finally, CYCLOSA achieves accuracy of Web search as it handles the real
query and the fake queries separately, in contrast to other existing solutions
that mix fake and real query results
Introducing Accountability to Anonymity Networks
Many anonymous communication (AC) networks rely on routing traffic through
proxy nodes to obfuscate the originator of the traffic. Without an
accountability mechanism, exit proxy nodes risk sanctions by law enforcement if
users commit illegal actions through the AC network. We present BackRef, a
generic mechanism for AC networks that provides practical repudiation for the
proxy nodes by tracing back the selected outbound traffic to the predecessor
node (but not in the forward direction) through a cryptographically verifiable
chain. It also provides an option for full (or partial) traceability back to
the entry node or even to the corresponding user when all intermediate nodes
are cooperating. Moreover, to maintain a good balance between anonymity and
accountability, the protocol incorporates whitelist directories at exit proxy
nodes. BackRef offers improved deployability over the related work, and
introduces a novel concept of pseudonymous signatures that may be of
independent interest.
We exemplify the utility of BackRef by integrating it into the onion routing
(OR) protocol, and examine its deployability by considering several
system-level aspects. We also present the security definitions for the BackRef
system (namely, anonymity, backward traceability, no forward traceability, and
no false accusation) and conduct a formal security analysis of the OR protocol
with BackRef using ProVerif, an automated cryptographic protocol verifier,
establishing the aforementioned security properties against a strong
adversarial model
An Anonymous System Based on Random Virtual Proxy Mutation
Anonymous systems are usually used to protect users\u27 privacy in network communication. However, even in the low-latency Tor system, it is accompanied by network communication performance degradation, which makes users have to give up using the anonymity system in many applications. Therefore, we propose a novel anonymity system with rotated multi-path accompanying virtual proxy mutation for data transmission. Unlike onion routing, in our system the randomly generated virtual proxies take over the address isolation executing directly on the network layer and expand the anonymity space to all terminals in the network. With the optimal algorithm of selecting the path, the network communication performance improved significantly also. The verification experiments show that the anonymity system terminal sends and receives data at 500 kbps, and only a slight delay jitter occurs at the receiving end, and the other network performance is not significantly reduced
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