For the beam splitter attack strategy against quantum key distribution using two-mode squeezed states,the analytical expression of the optimal beam splitter parameter is provided in this paper by applying the Shannon information theory.The theoretical secret information rate after error correction and privacy amplification is given in terms of the squeezed parameter and channel parameters.The results show that the two-mode squeezed state quantum key distribution is secure against an optimal beam splitter attack.
A quantum key distribution scheme for quantum cryptographic network is proposed, which is implemented physically by the Greenberger-Home-Zeilinger (GHZ) triplet state. Its security is guaranteed by the correlation of the GHZ triplet state, results show this protocol is unconditionally secure. The performance of the proposed protocol can reach 100\% in the idea circumstance. Application of the proposed protocol has also been discussed.
Lattice-based cryptosystems rely on certain lattice problems for their socurity, such as the shortest vector and the closest vector probtems. NTRU is a kind of lattice based public key cryptosysytem gaining much attention because of its high efficiency. Its encryption and decryption use a mixing system suggested by polynomial algebra combined with a clustering principle based on elementary probability theory. With the availability of quantum computers, the security of cryptosystems based on classical mathematic problems needs to be reevaluated. Since lattice reduction is the main threat to lattice-based cryptosystems, lattice reduction using quantum search algorithms are analyzed to evaluate the security of NTRU in this paper. According to our results, original security paratneters proposed for NTRU should be increased in the event that Grover's quantum search algorithm is used for lattice reduction.
