A general scheme for information interception in the ping pong protocol
This work provides a more robust theoretical foundation for eavesdropping in quantum communication, which is incremental but important for security analysis in quantum cryptography.
The authors addressed deficiencies in prior eavesdropping schemes for quantum direct communication by proposing a new generic scheme that works without losses and applies to any particle dimensionality, showing that some known attacks are special cases of it.
The existence of an undetectable eavesdropping of dense coded information has been already demonstrated by Pavičić for the quantum direct communication based on the ping-pong paradigm. However, a) the explicit scheme of the circuit is only given and no design rules are provided, b) the existence of losses is implicitly assumed, c) the attack has been formulated against qubit based protocol only and it is not clear whether it can be adapted to higher dimensional systems. These deficiencies are removed in the presented contribution. A new generic eavesdropping scheme built on a firm theoretical background is proposed. In contrast to the previous approach, it does not refer to the properties of the vacuum state, so it is fully consistent with the absence of losses assumption. Moreover, the scheme applies to the communication paradigm based on signal particles of any dimensionality. It is also shown that some well known attacks are special cases of the proposed scheme.