Jan-Åke Larsson

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—Unconditionally secure message authentication is an important part of quantum cryptography (QC). In this correspondence, we analyze security effects of using a key obtained from QC for authentication purposes in later rounds of QC. In particular, the eavesdropper gains partial knowledge on the key in QC that may have an effect on the security of the(More)
We derive a Gaussian approximation of the LLR distribution conditioned on the transmitted signal and the channel matrix for the soft-output via partial marginalization MIMO detector. This detector performs exact ML as a special case. Our main results consist of discussing the operational meaning of this approximation and a proof that, in the limit of high(More)
Quantum Cryptography, or more accurately, Quantum Key Distribution (QKD) is based on using an unconditionally secure " quantum channel " to share a secret key among two users. A manufacturer of QKD devices could, intentionally or not, use a (semi-)classical channel instead of the quantum channel, which would remove the supposedly unconditional security. One(More)
We demonstrate how adversaries with large computing resources can break Quantum Key Distribution (QKD) protocols which employ a particular message authentication code suggested previously. This authentication code, featuring low key consumption, is not Information-Theoretically Secure (ITS) since for each message the eavesdropper has intercepted she is able(More)
Information-theoretically secure (ITS) authentication is needed in Quantum Key Distribution (QKD). In this paper, we study security of an ITS authentication scheme proposed by Weg-man&Carter, in the case of partially known authentication key. This scheme uses a new authentication key in each authentication attempt, to select a hash function from an Almost(More)