Key Secrecy in a Quantum Cryptography System Based on Error-Correcting Codes

In [1], an algorithm based on error-correcting codes was proposed for generating a common key in information transmission through a quantum communication channel. In the present paper, we study the application of this algorithm in a quantum cryptography system where bits of key information are encoded by two nonorthogonal photon polarizations. An estimate for the key secrecy with respect to the “translucent” eavesdropping method is given in the form of a lower bound on the cardinality of the set of admissible key values.