We experimentally demonstrate that a superconducting nanowire single-photon detector is deterministically controllable by bright illumination. We found that bright light can temporarily make a large fraction of the nanowire length normally conductive, can extend deadtime after a normal photon detection, and can cause a hotspot formation during the deadtime with a highly nonlinear sensitivity. A...

We show that the claim of insecurity of the Y-00 (or αη) cryptosystem made by C. Ahn and K. Birnbaum in Phys. Lett. A 370 (2007) 131-135 even under ciphertextonly heterodyne attack, as well as the unfavorable security comparison between αη and an additive stream cipher for all kinds of attacks, is based on invalid extrapolations of Shannon’s random cipher analysis to two concrete ciphers and on...

We investigate the ability of a passive network observer to leverage third-party HTTP tracking cookies for mass surveillance. If two web pages embed the same tracker which emits a unique pseudonymous identifier, then the adversary can link visits to those pages from the same user (browser instance) even if the user’s IP address varies. Using simulated browsing profiles, we cluster network tra c...

We devise a simple modification that essentially doubles the efficiency of a well-known quantum key distribution scheme proposed by Bennett and Brassard (BB84). Our scheme assigns significantly different probabilities for the different polarization bases during both transmission and reception to reduce the fraction of discarded data. The actual probabilities used in the scheme are announced in ...

In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that the best strategy is actually to adopt the simple intercept/resend strategy.

We show that the claim of insecurity of the Y-00 (or αη) cryptosystem made by C. Ahn and K. Birnbaum in Phys. Lett. A 370 (2007) 131-135 even under ciphertextonly heterodyne attack, as well as the unfavorable security comparison between αη and an additive stream cipher for all kinds of attacks, is based on invalid extrapolations of Shannon’s random cipher analysis to two concrete ciphers. We ge...

The prepare-and-measure quantum key distribution (QKD) has the merits of fast speed, high key generation rate, and easy implementation. However, the detector side channel attacks greatly undermine the security of the key bits. The eavesdropper, Eve, exploits the flaws of the detectors to obtain illegal information without violating quantum principles. It means that she can intervene in the comm...

The theoretical Quantum Key-Distribution scheme of Bennett and Brassard (BB84) has been proven secure against very strong attacks including the collective attacks and the joint attacks. Though the latter are the most general attacks, collective attacks are much easier to analyze, yet, they are conjectured to be as informative to the eavesdropper. Thus, collective attacks are likely to be useful...

We show that the claim of insecurity of the Y-00 (or αη) cryptosystem made by C. Ahn and K. Birnbaum in Phys. Lett. A 370 (2007) 131-135 even under ciphertextonly heterodyne attack, as well as the unfavorable security comparison between αη and an additive stream cipher for all kinds of attacks, is based on invalid extrapolations of Shannon’s random cipher analysis to two concrete ciphers. We ge...