The Experts below are selected from a list of 17523 Experts worldwide ranked by ideXlab platform
Christian Kurtsiefer - One of the best experts on this subject based on the ideXlab platform.
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asymmetric delay attack on an entanglement based bidirectional Clock Synchronization protocol
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate an attack on a Clock Synchronization protocol that attempts to detect tampering of the Synchronization channel using polarization-entangled photon pairs. The protocol relies on a symmetrical channel, where propagation delays do not depend on the propagation direction, for correctly deducing the offset between Clocks—a condition that could be manipulated using optical circulators, which rely on static magnetic fields to break the reciprocity of propagating electromagnetic fields. Despite the polarization transformation induced within a set of circulators, our attack creates an error in time Synchronization while evading detection.
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symmetrical Clock Synchronization with time correlated photon pairs
Conference on Lasers and Electro-Optics, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a distance-independent Clock Synchronization protocol, using counter-propagating photons from spontaneous parametric down-conversion pair sources, secure against symmetric-delay attacks. With rates of 200 coincidences/s, we record a precision of 51 ps over 100 s. © 2019 The Author(s)
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symmetrical Clock Synchronization with time correlated photon pairs
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a point-to-point Clock Synchronization protocol based on bidirectionally exchanging photons produced in spontaneous parametric down conversion. The technique exploits tight timing correlations between photon pairs to achieve a precision of 51 ps in 100 s with count rates of order 200 s−1. The protocol is distance independent, is secure against symmetric delay attacks, and provides a natural complement to techniques based on Global Navigation Satellite Systems. The protocol works with mobile parties and can be augmented to provide authentication of the timing signal via a Bell inequality check.
Antia Lamaslinares - One of the best experts on this subject based on the ideXlab platform.
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asymmetric delay attack on an entanglement based bidirectional Clock Synchronization protocol
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate an attack on a Clock Synchronization protocol that attempts to detect tampering of the Synchronization channel using polarization-entangled photon pairs. The protocol relies on a symmetrical channel, where propagation delays do not depend on the propagation direction, for correctly deducing the offset between Clocks—a condition that could be manipulated using optical circulators, which rely on static magnetic fields to break the reciprocity of propagating electromagnetic fields. Despite the polarization transformation induced within a set of circulators, our attack creates an error in time Synchronization while evading detection.
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symmetrical Clock Synchronization with time correlated photon pairs
Conference on Lasers and Electro-Optics, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a distance-independent Clock Synchronization protocol, using counter-propagating photons from spontaneous parametric down-conversion pair sources, secure against symmetric-delay attacks. With rates of 200 coincidences/s, we record a precision of 51 ps over 100 s. © 2019 The Author(s)
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symmetrical Clock Synchronization with time correlated photon pairs
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a point-to-point Clock Synchronization protocol based on bidirectionally exchanging photons produced in spontaneous parametric down conversion. The technique exploits tight timing correlations between photon pairs to achieve a precision of 51 ps in 100 s with count rates of order 200 s−1. The protocol is distance independent, is secure against symmetric delay attacks, and provides a natural complement to techniques based on Global Navigation Satellite Systems. The protocol works with mobile parties and can be augmented to provide authentication of the timing signal via a Bell inequality check.
Jianwei Lee - One of the best experts on this subject based on the ideXlab platform.
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asymmetric delay attack on an entanglement based bidirectional Clock Synchronization protocol
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate an attack on a Clock Synchronization protocol that attempts to detect tampering of the Synchronization channel using polarization-entangled photon pairs. The protocol relies on a symmetrical channel, where propagation delays do not depend on the propagation direction, for correctly deducing the offset between Clocks—a condition that could be manipulated using optical circulators, which rely on static magnetic fields to break the reciprocity of propagating electromagnetic fields. Despite the polarization transformation induced within a set of circulators, our attack creates an error in time Synchronization while evading detection.
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symmetrical Clock Synchronization with time correlated photon pairs
Conference on Lasers and Electro-Optics, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a distance-independent Clock Synchronization protocol, using counter-propagating photons from spontaneous parametric down-conversion pair sources, secure against symmetric-delay attacks. With rates of 200 coincidences/s, we record a precision of 51 ps over 100 s. © 2019 The Author(s)
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symmetrical Clock Synchronization with time correlated photon pairs
Applied Physics Letters, 2019Co-Authors: Jianwei Lee, Lijiong Shen, Alessandro Cere, James Troupe, Antia Lamaslinares, Christian KurtsieferAbstract:We demonstrate a point-to-point Clock Synchronization protocol based on bidirectionally exchanging photons produced in spontaneous parametric down conversion. The technique exploits tight timing correlations between photon pairs to achieve a precision of 51 ps in 100 s with count rates of order 200 s−1. The protocol is distance independent, is secure against symmetric delay attacks, and provides a natural complement to techniques based on Global Navigation Satellite Systems. The protocol works with mobile parties and can be augmented to provide authentication of the timing signal via a Bell inequality check.
Christoph Lenzen - One of the best experts on this subject based on the ideXlab platform.
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Self-Stabilizing Byzantine Clock Synchronization with Optimal Precision
Theory of Computing Systems, 2019Co-Authors: Pankaj Khanchandani, Christoph LenzenAbstract:In the Byzantine-tolerant Clock Synchronization problem, the goal is to synchronize the Clocks of n fully connected nodes. The Clocks run at rates between 1 and > 1, and messages have a delay (including computation) between d − U and d . Moreover, up to f < n /3 of the nodes can fail by deviating arbitrarily from the protocol, i.e., are Byzantine. Despite this interference, correct nodes need to generate distinguished events (or pulses ) almost simultaneously and periodically. The quality of the solution is measured by the skew , which is the maximum real time difference between corresponding pulses. In the self-stabilizing setting, in addition we allow for transient failures, possibly of all nodes. Once transient faults have ceased and at most f nodes remain faulty, the system should start generating synchronized pulses again. We design a self-stabilizing solution to this problem with asymptotically optimal skew. We achieve our goal by refining and extending the protocol of Lynch and Welch and make the following contributions in the process. We give a simple analysis of the Lynch and Welch protocol with improved bounds on skew and tolerable difference in Clock rates by rebuilding upon the main ingredient of their protocol, called approximate agreement . We give a modified version of the protocol so that the frequency and amount of communication between the nodes is reduced. The modification adds a step to adjust the Clock rates by another application of approximate agreement. The skew bound achieved is asymptotically optimal for suitable choices of parameters. We present a method to add self-stabilization to the above protocols while preserving their skew bounds. The heart of the method is a coupling scheme that leverages a self-stabilizing protocol with a larger skew.
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self stabilizing byzantine Clock Synchronization with optimal precision
Theory of Computing Systems \ Mathematical Systems Theory, 2019Co-Authors: Pankaj Khanchandani, Christoph LenzenAbstract:In the Byzantine-tolerant Clock Synchronization problem, the goal is to synchronize the Clocks of n fully connected nodes. The Clocks run at rates between 1 and > 1, and messages have a delay (including computation) between d − U and d. Moreover, up to f < n/3 of the nodes can fail by deviating arbitrarily from the protocol, i.e., are Byzantine. Despite this interference, correct nodes need to generate distinguished events (or pulses) almost simultaneously and periodically. The quality of the solution is measured by the skew, which is the maximum real time difference between corresponding pulses. In the self-stabilizing setting, in addition we allow for transient failures, possibly of all nodes. Once transient faults have ceased and at most f nodes remain faulty, the system should start generating synchronized pulses again. We design a self-stabilizing solution to this problem with asymptotically optimal skew. We achieve our goal by refining and extending the protocol of Lynch and Welch and make the following contributions in the process.
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self stabilizing byzantine Clock Synchronization with optimal precision
arXiv: Distributed Parallel and Cluster Computing, 2016Co-Authors: Pankaj Khanchandani, Christoph LenzenAbstract:We revisit the approach to Byzantine fault-tolerant Clock Synchronization based on approximate agreement introduced by Lynch and Welch. Our contribution is threefold: (1) We provide a slightly refined variant of the algorithm yielding improved bounds on the skew that can be achieved and the sustainable frequency offsets. (2) We show how to extend the technique to also synchronize Clock rates. This permits less frequent communication without significant loss of precision, provided that Clock rates change sufficiently slowly. (3) We present a coupling scheme that allows to make these algorithms self-stabilizing while preserving their high precision. The scheme utilizes a low-precision, but self-stabilizing algorithm for the purpose of recovery.
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pulsesync an efficient and scalable Clock Synchronization protocol
IEEE ACM Transactions on Networking, 2015Co-Authors: Christoph Lenzen, Philipp Sommer, Roger WattenhoferAbstract:Clock Synchronization is an enabling service for a wide range of applications and protocols in both wired and wireless networks. We study the implications of Clock drift and communication latency on the accuracy of Clock Synchronization when scaling the network diameter. Starting with a theoretical analysis of Synchronization protocols, we prove tight bounds on the Synchronization error in a model that assumes independently and randomly distributed communication delays and slowly changing drifts. While this model is more optimistic than traditional worst-case analysis, it much better captures the nature of real-world systems such as wireless networks. The bound on the Synchronization accuracy, which is roughly the square root of the network diameter, is achieved by the novel PulseSync protocol. Extensive experiments demonstrate that PulseSync is able to meet the predictions from theory and tightly synchronizes large networks. This contrasts against an exponential growth of the skew incurred by the state-of-the-art protocol for wireless sensor networks. Moreover, PulseSync adapts much faster to network dynamics and changing Clock drifts than this protocol.
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tight bounds for Clock Synchronization
Journal of the ACM, 2010Co-Authors: Christoph Lenzen, Thomas Locher, Roger WattenhoferAbstract:We present a novel Clock Synchronization algorithm and prove tight upper and lower bounds on the worst-case Clock skew that may occur between any two participants in any given distributed system. More importantly, the worst-case Clock skew between neighboring nodes is (asymptotically) at most a factor of two larger than the best possible bound. While previous results solely focused on the dependency of the skew bounds on the network diameter, we prove that our techniques are optimal also with respect to the maximum Clock drift, the uncertainty in message delays, and the imposed bounds on the Clock rates. The presented results all hold in a general model where both the Clock drifts and the message delays may vary arbitrarily within pre-specified bounds.Furthermore, our algorithm exhibits a number of other highly desirable properties. First, the algorithm ensures that the Clock values remain in an affine linear envelope of real time. A better worst-case bound on the accuracy with respect to real time cannot be achieved in the absence of an external timer. Second, the algorithm minimizes the number and size of messages that need to be exchanged in a given time period. Moreover, only a small number of bits must be stored locally for each neighbor. Finally, our algorithm can easily be adapted for a variety of other prominent Synchronization models.
Todd E. Humphreys - One of the best experts on this subject based on the ideXlab platform.
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Requirements for Secure Clock Synchronization
IEEE Journal of Selected Topics in Signal Processing, 2018Co-Authors: Lakshay Narula, Todd E. HumphreysAbstract:This paper establishes a fundamental theory of secure Clock Synchronization. Accurate Clock Synchronization is the backbone of systems managing power distribution, financial transactions, telecommunication operations, database services, etc. Some Clock Synchronization (time transfer) systems, such as the global navigation satellite systems, are based on one-way communication from a master to a slave Clock. Others, such as the network transport protocol, and the IEEE 1588 precision time protocol (PTP), involve two-way communication between the master and slave. This paper shows that all one-way time transfer protocols are vulnerable to replay attacks that can potentially compromise timing information. A set of conditions for secure two-way Clock Synchronization is proposed and proved to be necessary and sufficient. It is shown that IEEE 1588 PTP, although a two-way Synchronization protocol, is not compliant with these conditions, and is therefore insecure. Requirements for secure IEEE 1588 PTP are proposed, and a second example protocol is offered to illustrate the range of compliant systems.