Guessing probability under unlimited known-plaintext attack on secret keys for Y00 quantum stream cipher by quantum multiple hypotheses testing
This work addresses security concerns for the Y00 quantum communication protocol, which is incremental as it provides new insights but builds on existing evaluations.
The study tackled the security of the Y00 quantum stream cipher by evaluating the guessing probabilities on shared secret keys under unlimited known-plaintext attacks, finding that eavesdroppers can only guess keys of limited lengths with a probability strictly less than 1.
Although quantum key distribution is regarded as promising secure communication, security of Y00 protocol proposed by Yuen in 2000 for the affinity to conventional optical communication is not well-understood yet; its security has been evaluated only by the eavesdropper's error probabilities of detecting individual signals or masking size, the number of hidden signal levels under quantum and classical noise. Our study is the first challenge of evaluating the guessing probabilities on shared secret keys for pseudorandom number generators in a simplified Y00 communication system based on quantum multiple hypotheses testing theory. The result is that even unlimitedly long known-plaintext attack only lets the eavesdropper guess the shared secret keys of limited lengths with a probability strictly < 1. This study will give some insights for detailed future works on this quantum communication protocol.