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Quantum Key Secured 100 Gbit/s Payload Encryption and its High-Speed Network Interfaces

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This picture shows a 3D model of the new version of the PCB. All network connections are now located on the top side of the board, making it suitable for dense housing in racks.


2010 - 2013


Christoph Keller
Norbert Felber
Frank K. Gurkaynak


Nano-Tera: Qcrypt


ID Quantique
Group of Applied Physics, University of Geneva
Institut Reconfigurable & Embedded Digital Systems, HES-SO, Yverdon


Quantum Key Distribution (QKD) ensures attack-resilient exchange of cipher keys, while classical encryption provides secure transmission of information at highest data rates. The research task of ETHZ-IIS and HESSO-REDS in the nano-tera project QCRYPT was the development of the 100 Gbit/s link encryptor system with a variety of optical interfaces on the plain-text side and a 100 Gbit/s optical link to securely bridge large distances between encryptors.

During the third year of the project, the main focus lay on the development of a second version of the PCB for this system. The layer stackup was modified to enhance the high-frequency quality of the 10 Gbit/s differential lines and to meet the requirements for industrial manufacturing in large quantities. A PCI Express cable interface was included, which is used for the configuration and management of the board and for the quantum key transfer. Electronic dispersion compensation ICs have been included on six of ten 10 Gbit/s SFP+ Ethernet links to improve the optical fiber lengths on the user interfaces.

The network and encryption functions have been finalized and extensively tested. A new scheme for time-division multiplexing (TDM) has been introduced which reduces the average latency and led to some simplifications of the design. The total latency is 3.3 μs, plus optical fiber delay, over the whole encrypted link.

TDM and encryption is now fully transparent between corresponding 10 Gbit/s user interfaces. Moreover, Jumbo Frames, i.e. Ethernet frames larger than 1540 Bytes, are now also supported.