A new paper, entitled “An FPGA-based 4Mbps Secret Key Distillation Engine for Quantum Key Distribution Systems” and co-authored with Jeremy Constantin, Nicholas Preyss and Andreas Burg (EPFL), Raphaël Houlmann and Hugo Zbinden (University of Geneva), Nino Walenta (Batelle) and myself has been accepted for publication in Springer’s Journal of Signal Processing Systems.
Here is its abstract:
Quantum key distribution (QKD) enables provably secure communication between two parties over an optical fiber that arguably withstands any form of attack. Besides the need for a suitable physical signalling scheme and the corresponding devices, QKD also requires a secret key distillation protocol. This protocol and the involved signal processing handle the reliable key agreement process over the fragile quantum channel, as well as the necessary post-processing of key bits to avoid leakage of secret key information to an eavesdropper. In this paper we present in detail an implementation of a key distillation engine for a QKD system based on the coherent one-way (COW) protocol. The processing of key bits by the key distillation engine includes agreement on quantum bit detections (sifting), information reconciliation with forward error correction coding, parameter estimation, and privacy amplification over an authenticated channel. We detail the system architecture combining all these processing steps, and discuss the design trade-offs for each individual system module. We also assess the performance and efficiency of our key distillation implementation in terms of throughput, error correction capabilities, and resource utilization. On a single-FPGA (Xilinx Virtex-6 LX240T) platform, the system supports distilled key rates of up to 4 Mbps.
Co-authored with Benjamin Wesoloswki, now a Ph.D. student at EPFL, a new paper entitled Ciphertext-Policy Attribute-Based Broadcast Encryption with Small Keys has been made available on the IACR E-print archive. Here is its abstract:
Broadcasting is a very efficient way to securely transmit information to a large set of geographically scattered receivers, and in practice, it is often the case that these receivers can be grouped in sets sharing common characteristics (or attributes). We describe in this paper an efficient ciphertext-policy attribute-based broadcast encryption scheme (CP-ABBE) supporting negative attributes and able to handle access policies in conjunctive normal form (CNF). Essentially, our scheme is a combination of the Boneh-Gentry-Waters broadcast encryption and of the Lewko-Sahai-Waters revocation schemes; the former is used to express attribute-based access policies while the latter is dedicated to the revocation of individual receivers. Our scheme is the first one that involves a public key and private keys having a size that is independent of the number of receivers registered in the system. Its selective security is proven with respect to the Generalized Diffie-Hellman Exponent (GDHE) problem on bilinear groups.
The QCrypt project, funded by the Nano-Tera program, is gently terminating. QCrypt involves ID Quantique SA in Geneva, the University of Geneva through its Applied Physics Group, the EPFL, through the Telecommunications Circuits Laboratory, the ETH Zürich, through the Integrated Systems Laboratory, and the HES-SO, through two institutes of the HEIG-VD (REDS and IICT) as well as the hepia.
The QCrypt project purpose consisted mainly in building a next-generation quantum key distribution system integrated with a 100 Gb/s layer-2 encryptor relying on classical cryptography.
A first paper has been uploaded to arXiv recently, which discusses the technical aspects of the QKD engine. Co-written with 20 (!) authors, it describes for the first time, to the best of our knowledge, the throughput achievable in practice of (distilled) key bits for a pre-defined security level when taking into account finite-key effects, authentication costs and the composability of keys. Here is the paper’s abstract:
We present a 625 MHz clocked coherent one-way quantum key distribution (QKD) system which continuously distributes secret keys over an optical fibre link. To support high secret key rates, we implemented a fast hardware key distillation engine which allows for key distillation rates up to 4 Mbps in real time. The system employs wavelength multiplexing in order to run over only a single optical fibre and is compactly integrated in 19-inch 2U racks. We optimized the system considering a security analysis that respects finite-key-size effects, authentication costs, and system errors. Using fast gated InGaAs single photon detectors, we reliably distribute secret keys with rates up to 140 kbps and over 25 km of optical fibre, for a security parameter of 4E-9.