We introduce a new integral method for Quantum Key Distribution to perform sifting, reconciliation and amplification processes to establish a cryptographic key through the use of binary structures called frames which are capable to increase quadratically the secret key rate. The method can be implemented with the usual optical Bennett-Brassard (BB84) equipment allowing strong pulses in the quantum regime.

Abstract:Despite the unconditionally secure theory of the Quantum Key Distribution (QKD), several attacks have been successfully implemented against commercial QKD systems. Those systems have exhibited some flaws, as the secret key rate of corresponding protocols remains unaltered, while the eavesdropper obtains the entire secret key. We propose the negative acknowledgment state quantum key distribution protocol as a novel protocol capable of detecting the eavesdropping activity of the Intercept Resend with Faked Sates (IRFS) attack without requiring additional optical components different from the BB84 protocol because the system can be implemented as a high software module. In this approach, the transmitter interleaves pairs of quantum states, referred to here as parallel and orthogonal states, while the receiver uses active basis selection.

Physical implementations of quantum key distribution (QKD) protocols, like the Bennett-Brassard (BB84), are forced to use attenuated coherent quantum states, because the sources of single photon states are not functional yet for QKD applications. However, when using attenuated coherent states, the relatively high rate of multi-photonic pulses introduces vulnerabilities that can be exploited by the photon number splitting (PNS) attack to brake the quantum key. Some QKD protocols have been developed to be resistant to the PNS attack, like the decoy method, but those define a single photonic gain in the quantum channel. To overcome this limitation, we have developed a new QKD protocol, called ack-QKD, which is resistant to the PNS attack. Even more, it uses attenuated quantum states, but defines two interleaved photonic quantum flows to detect the eavesdropper activity by means of the quantum photonic error gain (QPEG) or the quantum bit error rate (QBER). The physical implementation of the ack-QKD is similar to the well-known BB84 protocol.

We investigate a cryptosystem through what we call non-invertible cryptography. As a result of a continuous refinement process, we present a new key exchange method to establish a secret key between two remote parties. Non-invertible KEP is supported by Euler’s theorem as RSA, it uses exponentiation to exchange a secret key as Diffie–Hellman, and it encrypts/decrypts through invertible multiplication as ElGamal. This method is public key; it allows secret key exchange and performs secret communication. Most remarkably, since it does not rely on computational problems as integer factorization or discrete logarithm whose difficulty is conjectured, non-invertible KEP becomes a promising candidate to protect communication in the quantum era. By contrast, the algorithm is supported on indistinguishability of public key and ciphertext so it achieves perfect secrecy. The protocol demonstrates minimum required time for encryption/decryption processes when is compared with the main public key algorithms as Diffie–Hellman, ElGamal or RSA.

We present a new post-processing method for Quantum Key Distribution (QKD) that raises cubically the secret key rate in the number of double matching detection events. In Shannon’s communication model, information is prepared at Alice’s side, and it is then intended to pass it over a noisy channel. In our approach, secret bits do not rely in Alice’s transmitted quantum bits but in Bob’s basis measurement choices. Therefore, measured bits are publicly revealed, while bases selections remain secret. Our method implements sifting, reconciliation, and amplification in a unique process, and it just requires a round iteration; no redundancy bits are sent, and there is no limit in the correctable error percentage. Moreover, this method can be implemented as a post-processing software into QKD technologies already in use.