Quantum public-key encryption schemes based on conjugate coding

We present several quantum public-key encryption (QPKE) protocols designed using conjugate coding single-photon strings; thus, they may be realized in the laboratory using current techniques. The first two schemes can encrypt one-bit messages; these are then extended to two kinds of QPKE schemes oriented toward multi-bit messages. In these schemes, Boolean functions are used as private keys and classical-quantum pairs as public keys, where one private key corresponds to an exponential number of public keys. Later, we discuss some issues related to authentication and a possible way to improve the security of the proposed schemes in this paper. The novel structure of the protocols presented here ensures that most of them are information-theoretic secure under attacks on the private key and on the encryption, while they can be realized more easily compared to other protocols.