49,204 research outputs found
CryptoMaze: Atomic Off-Chain Payments in Payment Channel Network
Payment protocols developed to realize off-chain transactions in Payment
channel network (PCN) assumes the underlying routing algorithm transfers the
payment via a single path. However, a path may not have sufficient capacity to
route a transaction. It is inevitable to split the payment across multiple
paths. If we run independent instances of the protocol on each path, the
execution may fail in some of the paths, leading to partial transfer of funds.
A payer has to reattempt the entire process for the residual amount. We propose
a secure and privacy-preserving payment protocol, CryptoMaze. Instead of
independent paths, the funds are transferred from sender to receiver across
several payment channels responsible for routing, in a breadth-first fashion.
Payments are resolved faster at reduced setup cost, compared to existing
state-of-the-art. Correlation among the partial payments is captured,
guaranteeing atomicity. Further, two party ECDSA signature is used for
establishing scriptless locks among parties involved in the payment. It reduces
space overhead by leveraging on core Bitcoin scripts. We provide a formal model
in the Universal Composability framework and state the privacy goals achieved
by CryptoMaze. We compare the performance of our protocol with the existing
single path based payment protocol, Multi-hop HTLC, applied iteratively on one
path at a time on several instances. It is observed that CryptoMaze requires
less communication overhead and low execution time, demonstrating efficiency
and scalability.Comment: 30 pages, 9 figures, 1 tabl
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
Revisiting Deniability in Quantum Key Exchange via Covert Communication and Entanglement Distillation
We revisit the notion of deniability in quantum key exchange (QKE), a topic
that remains largely unexplored. In the only work on this subject by Donald
Beaver, it is argued that QKE is not necessarily deniable due to an
eavesdropping attack that limits key equivocation. We provide more insight into
the nature of this attack and how it extends to other constructions such as QKE
obtained from uncloneable encryption. We then adopt the framework for quantum
authenticated key exchange, developed by Mosca et al., and extend it to
introduce the notion of coercer-deniable QKE, formalized in terms of the
indistinguishability of real and fake coercer views. Next, we apply results
from a recent work by Arrazola and Scarani on covert quantum communication to
establish a connection between covert QKE and deniability. We propose DC-QKE, a
simple deniable covert QKE protocol, and prove its deniability via a reduction
to the security of covert QKE. Finally, we consider how entanglement
distillation can be used to enable information-theoretically deniable protocols
for QKE and tasks beyond key exchange.Comment: 16 pages, published in the proceedings of NordSec 201
Anonymity for practical quantum networks
Quantum communication networks have the potential to revolutionise
information and communication technologies. Here we are interested in a
fundamental property and formidable challenge for any communication network,
that of guaranteeing the anonymity of a sender and a receiver when a message is
transmitted through the network, even in the presence of malicious parties. We
provide the first practical protocol for anonymous communication in realistic
quantum networks.Comment: 5 pages, published versio
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