Information-theoretic security proof for quantum-key-distribution protocols

Abstract

We present a technique for proving the security of quantum-key-distribution ͑QKD͒ protocols. It is based on direct information-theoretic arguments and thus also applies if no equivalent entanglement purification scheme can be found. Using this technique, we investigate a general class of QKD protocols with one-way classical post-processing. We show that, in order to analyze the full security of these protocols, it suffices to consider collective attacks. Indeed, we give new lower and upper bounds on the secret-key rate which only involve entropies of two-qubit density operators and which are thus easy to compute. As an illustration of our results, we analyze the Bennett-Brassard 1984, the six-state, and the Bennett 1992 protocols with one-way error correction and privacy amplification. Surprisingly, the performance of these protocols is increased if one of the parties adds noise to the measurement data before the error correction. In particular, this additional noise makes the protocols more robust against noise in the quantum channel.

Decoherence in quantum walks – a review

“…An example from the field of quantum information may be found in Kraus et al (2005) and Renner et al (2005), where the security of a quantum secret key is increased by adding a small amount of randomness to the key during the privacy amplification stage of the protocol. This can be understood in two ways.…”

Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks

“…[9,10]. Here, we limit ourselves to the asymptotic key limit as the number of entries n in the raw key y tend to infinity.…”

“…We consider the class of collective attacks [9,10], thereby limiting Eve's possible interaction with the signal states. In this scenario, Eve can only interact with each signal individually, but she can store these quantum states for later usage.…”

Distributed authentication for randomly compromised networks

“…It can successfully perform MITM attacks against public key cryptosystems (using the first capability) and against unauthenticated QKD (using the second capability) but not against a QKD link between two uncompromised nodes that share a secret key for authentication (since quantum mechanics allows the eavesdropping to be detected) [10]. The adversary can always perform denial-ofservice (DOS) attacks by simply destroying all transmitted information; since DOS attacks cannot be prevented in this adversarial scenario, we concern ourselves only with security against MITM attacks and do not consider robustness against DOS attacks further.…”