Polarity inversion attack prevention by physical properties of Y00 quantum stream cipher

Abstract

This paper presents the physical prevention probability of an Intensity-Shift-Keying (ISK) Y00 quantum stream cipher against a polarity inversion attack, where the attacker in the middle of the communication line intercepts legitimate sender’s messages and resends false messages to the legitimate receiver by inverting some of signal polarities. Message falsification is recognized as a major issue in the field of mathematical encryption. Therefore, the attack should also be studied in the field of physical encryption. Y00 protocol was proposed by H. P. Yuen in 2000 to hide even ciphertexts from eavesdroppers under quantum noise of coherent light. Theoretical and experimental analyses of encryption strength of Y00 systems have also been studied against eavesdropping. However, there were not many studies about active attacks like message falsifications. Recent studies showed that the present ISK Y00 systems, whose communication bases are paired signals, may prevent the attack under the Known-Plaintext-Attack. To enhance the probability against the attack, a quadruple-signal-based ISK Y00 system was proposed, whose signal bases are sets of 4 signals. This study shows the proposed system has a prevention probability of 0.66665 per signal, while One-Time Pad used in BB84 cannot prevent message falsification under Known-Plaintext-Attack since polarity inversion directly falsifies the message.