CPC H04L 9/0838 (2013.01) [H04L 9/0825 (2013.01); H04L 9/085 (2013.01); H04L 9/0869 (2013.01)] | 13 Claims |
1. A method for determining a secret cryptographic key shared between a sending unit and a receiving unit for secure communication, the method comprising:
a first step of obtaining, by the sending unit, a random bit sequence R,
a second step of transmitting, at the sending unit, a first sequence of electromagnetic pulses to the receiving unit via a communication channel, wherein each electromagnetic pulse of the first sequence of electromagnetic pulses corresponds to a bit of the random bit sequence R according to a ciphering protocol; wherein the ciphering protocol comprises assigning a bit of the random bit sequence R with bit value 0 to a first quantum state and a bit of the random bit sequence R with bit value 1 to a second quantum state;
a third step of receiving, at the receiving unit, a second sequence of electromagnetic pulses corresponding to the transmitted first sequence of electromagnetic pulses, and deciphering the second sequence of electromagnetic pulses based on the ciphering protocol,
a fourth step of performing information reconciliation based on the received second sequence of electromagnetic pulses in order to establish a shared bit sequence, and
a fifth step of determining a signal loss rE in the communication channel caused by an eavesdropper,
a sixth step of estimating an information advantage ΔI over the eavesdropper based on the degree of indistinguishability between the first quantum state and the second quantum state, the determined signal loss rE caused by the eavesdropper and an intrinsic signal loss r0 in the communication channel, the degree of indistinguishability between the first quantum state and the second quantum state being the absolute value of the overlap matrix element of the first quantum state and the second quantum state, the information advantage ΔI being estimated by subtracting the maximum of information gained by the eavesdropper about the shared bit sequence from mutual information of the sending unit and receiving unit, and
a seventh step of performing privacy amplification based on the shared bit sequence and the estimated information advantage ΔI in order to establish a shared secret cryptographic key.
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