18 research outputs found
After-gate attack on a quantum cryptosystem
We present a method to control the detection events in quantum key
distribution systems that use gated single-photon detectors. We employ bright
pulses as faked states, timed to arrive at the avalanche photodiodes outside
the activation time. The attack can remain unnoticed, since the faked states do
not increase the error rate per se. This allows for an intercept-resend attack,
where an eavesdropper transfers her detection events to the legitimate receiver
without causing any errors. As a side effect, afterpulses, originating from
accumulated charge carriers in the detectors, increase the error rate. We have
experimentally tested detectors of the system id3110 (Clavis2) from ID
Quantique. We identify the parameter regime in which the attack is feasible
despite the side effect. Furthermore, we outline how simple modifications in
the implementation can make the device immune to this attack.Comment: 14 pages, 8 figure
Device calibration impacts security of quantum key distribution
Characterizing the physical channel and calibrating the cryptosystem hardware
are prerequisites for establishing a quantum channel for quantum key
distribution (QKD). Moreover, an inappropriately implemented calibration
routine can open a fatal security loophole. We propose and experimentally
demonstrate a method to induce a large temporal detector efficiency mismatch in
a commercial QKD system by deceiving a channel length calibration routine. We
then devise an optimal and realistic strategy using faked states to break the
security of the cryptosystem. A fix for this loophole is also suggested.Comment: 4 pages + 1 page of supplementary information. Considerable
modification of Eve's attack strategy and QBER minimization technique. All
figures have also been improve
Dead-time optimization to increase secure distance range in prepare and measure quantum key distribution protocols
Afterpulsing is a factor limiting the distance over which discrete-variable
quantum key distribution systems are secure, and a common feature in
single-photon detectors. The relevance of this phenomenon stems from its
stochastic, self-interacting nature and the fact that its rate rises with the
number of avalanche events, which increases the quantum bit error rate. Here we
introduce an effective analytic model, including dead-time and afterpulsing
corrections, where afterpulsing correction depends on dead-time value. This
model is useful to evaluate the performance of prepare and measure quantum key
distribution protocols (standard and decoy versions) that use gated single
photon detectors. The model provides an expression to numerically optimize the
secret key rate over the full distance range for secure communication, enabling
in this way the calculation of quantum bit error rate and secure key rate. In
the conventional procedure, the dead-time value is fixed regardless of
distance, limiting the distance range of the channel due to remaining
afterpulsing effects, which are more relevant at higher operating frequencies.
Here we demonstrate that optimizing the dead-time values increases the distance
range of the channel to share secret keys.Comment: 13 pages, 9 figure
Witnessing effective entanglement over a 2km fiber channel
We present a fiber-based continuous-variable quantum key distribution system.
In the scheme, a quantum signal of two non-orthogonal weak optical coherent
states is sent through a fiber-based quantum channel. The receiver
simultaneously measures conjugate quadratures of the light using two homodyne
detectors. From the measured Q-function of the transmitted signal, we estimate
the attenuation and the excess noise caused by the channel. The estimated
excess noise originating from the channel and the channel attenuation including
the quantum efficiency of the detection setup is investigated with respect to
the detection of effective entanglement. The local oscillator is considered in
the verification. We witness effective entanglement with a channel length of up
to 2km.Comment: 11 pages, 5 figure
Thermal blinding of gated detectors in quantum cryptography
It has previously been shown that the gated detectors of two commercially
available quantum key distribution (QKD) systems are blindable and controllable
by an eavesdropper using continuous-wave illumination and short bright trigger
pulses, manipulating voltages in the circuit [L. Lydersen et al., Nat.
Photonics DOI:10.1038/nphoton.2010.214]. This allows for an attack
eavesdropping the full raw and secret key without increasing the quantum bit
error rate (QBER). Here we show how thermal effects in detectors under bright
illumination can lead to the same outcome. We demonstrate that the detectors in
a commercial QKD system Clavis2 can be blinded by heating the avalanche photo
diodes (APDs) using bright illumination, so-called thermal blinding. Further,
the detectors can be triggered using short bright pulses once they are blind.
For systems with pauses between packet transmission such as the plug-and-play
systems, thermal inertia enables Eve to apply the bright blinding illumination
before eavesdropping, making her more difficult to catch.Comment: 10 pages, 12 figure
Hacking commercial quantum cryptography systems by tailored bright illumination
The peculiar properties of quantum mechanics allow two remote parties to
communicate a private, secret key, which is protected from eavesdropping by the
laws of physics. So-called quantum key distribution (QKD) implementations
always rely on detectors to measure the relevant quantum property of single
photons. Here we demonstrate experimentally that the detectors in two
commercially available QKD systems can be fully remote-controlled using
specially tailored bright illumination. This makes it possible to tracelessly
acquire the full secret key; we propose an eavesdropping apparatus built of
off-the-shelf components. The loophole is likely to be present in most QKD
systems using avalanche photodiodes to detect single photons. We believe that
our findings are crucial for strengthening the security of practical QKD, by
identifying and patching technological deficiencies.Comment: Revised version, rewritten for clarity. 5 pages, 5 figures. To
download the Supplementary information (which is in open access), go to the
journal web site at http://dx.doi.org/10.1038/nphoton.2010.21
Lecturas de política monetaria y financiera
1 archivo PDF (487 páginas)Conjunto de trabajos de investigadores especializados en teoría monetaria y financiera, que presentan un análisis teórico y empírico de los cambios de la economía mexicana, propuestas y críticas tanto de los procesos mismos cómo de las políticas con que enfrentan las autoridades monetarias nacionales el reto que implica la mayor integración del sistema mexicano al internacional. Las investigaciones se agrupan en seis secciones temáticas: Política monetaria y cambiaria; Influencia de los flujos internacionales de capital; La política monetaria y sus relaciones con la inflación; Sector financiero, crisis y política económica; Sector bursátil y Marco Legal
Distribution and ecology of parent taxa of pollen lodged within the Latin American Pollen Database
The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The 'dictionary' describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.Fil: Marchant, Robert. University of Amsterdam; Países BajosFil: Almeida, Lucía. Universidad Nacional Autónoma de México; MéxicoFil: Behling, Hermann. Center for Tropical Maritime Ecology; AlemaniaFil: Berrio, Juan Carlos. University of Amsterdam; Países BajosFil: Bush, Mark. West University Boulevard; Estados UnidosFil: Cleef, Antoine. University of Amsterdam; Países BajosFil: Duivenvoorden, Joost. University of Amsterdam; Países BajosFil: Kappelle, Maarten. Instituto Nacional de Biodiversidad (INBio); Costa RicaFil: De Oliveira, Paulo. Universidade de Sao Paulo; BrasilFil: de Oliveira, Ary Teixeira. Universidade Federal de Lavras; BrasilFil: Lozano García, Socorro. Universidad Nacional Autónoma de México; MéxicoFil: Hooghiemstra, Henry. University of Amsterdam; Países BajosFil: Ledru, Marie Pierre. Instituto de Geociencias; BrasilFil: Ludlow Wiechers, Beatriz. Universidad Nacional Autónoma de México; MéxicoFil: Markgraf, Vera. University of Colorado; Estados UnidosFil: Mancini, Maria Virginia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Paez, Marta Mercedes. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Prieto, Aldo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Laboratorio de Paleoecología y Palinología; ArgentinaFil: Rangel, Olando. Universidad Nacional de Colombia; ColombiaFil: Salgado Labouriau, Maria Lea. Universidade do Brasília; Brasi
After-gate attack on a quantum cryptosystem
We present a method to control the detection events in quantum key
distribution systems that use gated single-photon detectors. We employ bright
pulses as faked states, timed to arrive at the avalanche photodiodes outside the
activation time. The attack can remain unnoticed, since the faked states do not
increase the error rate per se. This allows for an intercept–resend attack, where
an eavesdropper transfers her detection events to the legitimate receiver without
causing any errors. As a side effect, afterpulses, originating from accumulated
charge carriers in the detectors, increase the error rate. We have experimentally
tested detectors of the system id3110 (Clavis2) from ID Quantique. We identify
the parameter regime in which the attack is feasible despite the side effect.
Furthermore, we outline how simple modifications in the implementation can
make the device immune to this attack