Key expansion for qkd

Abstract

A method of encrypting information using an encryption pad based on keys exchanged between quantum key distribution (QKD) stations is disclosed. The method includes establishing raw keys between two stations using QKD, processing the keys to establish a plurality of matching privacy amplified keys at each station and buffering the keys in a shared key schedule. The method also includes the option of expanding one or more of the keys in the shared key schedule using a stream cipher to create a supply of expanded keys that serve as pads for one-time-pad encryption.

Description

CLAIM OF PRIORITY [0001] This patent application claims priority from U.S. Provisional Patent Application No. 60 / 445,805, filed on Feb. 7, 2003.TECHNICAL FIELD [0002] The present invention relates to quantum cryptography, and in particular relates to key expansion methods applied to keys established between quantum key distribution (QKD) stations for the purpose of forming one-time pads for sending encrypted information between the QKD stations. BACKGROUND ART [0003] Quantum key distribution involves establishing a key between a sender (“Alice”) and a receiver (“Bob”) by using weak (e.g., 0.1 photon on average) optical signals transmitted over a “quantum channel.” The security of the key distribution is based on the quantum mechanical principal that any measurement of a quantum system in unknown state will modify its state. As a consequence, an eavesdropper (“Eve”) that attempts to intercept or otherwise measure the quantum signal will introduce errors into the transmitted signals, ...

AI Technical Summary

Benefits of technology

"The present invention relates to a method for expanding the key in a quantum key distribution (QKD) system without having to send additional photons over the system. This is achieved by using a method called \"privacy amplification\" which deducs the number of bits needed to form the final key and ensures that any information an eavesdropper has about the final key is lower than a specified value. The invention also allows QKD to encrypt broadband streams of data, providing a method for expanding the key without having to send additional photons over the system."

Problems solved by technology

As a consequence, an eavesdropper (“Eve”) that attempts to intercept or otherwise measure the quantum signal will introduce errors into the transmitted signals, thereby revealing her presence.

The secure key rate from a QKD system is usually too low for commercially available data transmission lines if one-time pad encryption is being used.

Also, the achievable data bandwidth is very low and is limited by the key generation rate, which is around 1-10 kbps with present technology.

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