330 research outputs found
Practical and Provably Secure Onion Routing
In an onion routing protocol, messages travel through several intermediaries before arriving at their destinations; they are wrapped in layers of encryption (hence they are called "onions"). The goal is to make it hard to establish who sent the message. It is a practical and widespread tool for creating anonymous channels.
For the standard adversary models - passive and active - we present practical and provably secure onion routing protocols. Akin to Tor, in our protocols each party independently chooses the routing paths for his onions. For security parameter lambda, our differentially private solution for the active adversary takes O(log^2 lambda) rounds and requires every participant to transmit O(log^{4} lambda) onions in every round
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
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A twoâstep authentication framework for Mobile ad hoc networks
The lack of fixed infrastructure in ad hoc networks causes nodes to rely more heavily on peer nodes for communication. Nevertheless, establishing trust in such a distributed environment is very difficult, since it is not straightforward for a node to determine if its peer nodes can be trusted. An additional concern in such an environment is with whether a peer node is merely relaying a message or if it is the originator of the message. In this paper, we propose an authentication approach for protecting nodes in mobile ad hoc networks. The security requirements for protecting data link and network layers are identified and the design criteria for creating secure ad hoc networks using several authentication protocols are analyzed. Protocols based on zero knowledge and challenge response techniques are presented and their performance is evaluated through analysis and simulation
Seeking Anonymity in an Internet Panopticon
Obtaining and maintaining anonymity on the Internet is challenging. The state
of the art in deployed tools, such as Tor, uses onion routing (OR) to relay
encrypted connections on a detour passing through randomly chosen relays
scattered around the Internet. Unfortunately, OR is known to be vulnerable at
least in principle to several classes of attacks for which no solution is known
or believed to be forthcoming soon. Current approaches to anonymity also appear
unable to offer accurate, principled measurement of the level or quality of
anonymity a user might obtain.
Toward this end, we offer a high-level view of the Dissent project, the first
systematic effort to build a practical anonymity system based purely on
foundations that offer measurable and formally provable anonymity properties.
Dissent builds on two key pre-existing primitives - verifiable shuffles and
dining cryptographers - but for the first time shows how to scale such
techniques to offer measurable anonymity guarantees to thousands of
participants. Further, Dissent represents the first anonymity system designed
from the ground up to incorporate some systematic countermeasure for each of
the major classes of known vulnerabilities in existing approaches, including
global traffic analysis, active attacks, and intersection attacks. Finally,
because no anonymity protocol alone can address risks such as software exploits
or accidental self-identification, we introduce WiNon, an experimental
operating system architecture to harden the uses of anonymity tools such as Tor
and Dissent against such attacks.Comment: 8 pages, 10 figure
Dark clouds on the horizon:the challenge of cloud forensics
We introduce the challenges to digital forensics introduced by the advent and adoption of technologies, such as encryption, secure networking, secure processors and anonymous routing. All potentially render current approaches to digital forensic investigation unusable. We explain how the Cloud, due to its global distribution and multi-jurisdictional nature, exacerbates these challenges. The latest developments in the computing milieu threaten a complete âevidence blackoutâ with severe implications for the detection, investigation and prosecution of cybercrime. In this paper, we review the current landscape of cloud-based forensics investigations. We posit a number of potential solutions. Cloud forensic difficulties can only be addressed if we acknowledge its socio-technological nature, and design solutions that address both human and technological dimensions. No firm conclusion is drawn; rather the objective is to present a position paper, which will stimulate debate in the area and move the discipline of digital cloud forensics forward. Thus, the paper concludes with an invitation to further informed debate on this issue
On the Complexity of Anonymous Communication Through Public Networks
Onion routing is the most widely used approach to anonymous communication
online. The idea is that Alice wraps her message to Bob in layers of encryption
to form an "onion," and routes it through a series of intermediaries. Each
intermediary's job is to decrypt ("peel") the onion it receives to obtain
instructions for where to send it next, and what to send. The intuition is
that, by the time it gets to Bob, the onion will have mixed with so many other
onions, that its origin will be hard to trace even for an adversary that
observes the entire network and controls a fraction of the participants,
possibly including Bob.
In spite of its widespread use in practice, until now no onion routing
protocol was known that simultaneously achieved, in the presence of an active
adversary that observes all network traffic and controls a constant fraction of
the participants, (a) fault-tolerance, where even if a few of the onions are
dropped, the protocol still delivers the rest; (b) reasonable communication and
computational complexity as a function of the security parameter and the number
of participants; and (c) anonymity.
In this paper, we give the first onion routing protocol that meets these
goals: our protocol (a) tolerates a polylogarithmic (in the security parameter)
number of dropped onions and still delivers the rest; (b) requires a
polylogarithmic number of rounds and a polylogarithmic number of onions sent
per participant per round; and (c) achieves anonymity. We also show that to
achieve anonymity in a fault-tolerant fashion via onion routing, this number of
onions and rounds is necessary.
Of independent interest, our analysis introduces two new security properties
of onion routing -- mixing and equalizing -- and we show that together they
imply anonymity
TARANET: Traffic-Analysis Resistant Anonymity at the NETwork layer
Modern low-latency anonymity systems, no matter whether constructed as an
overlay or implemented at the network layer, offer limited security guarantees
against traffic analysis. On the other hand, high-latency anonymity systems
offer strong security guarantees at the cost of computational overhead and long
delays, which are excessive for interactive applications. We propose TARANET,
an anonymity system that implements protection against traffic analysis at the
network layer, and limits the incurred latency and overhead. In TARANET's setup
phase, traffic analysis is thwarted by mixing. In the data transmission phase,
end hosts and ASes coordinate to shape traffic into constant-rate transmission
using packet splitting. Our prototype implementation shows that TARANET can
forward anonymous traffic at over 50~Gbps using commodity hardware
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