| CPC H04L 9/0852 (2013.01) [G06N 3/084 (2013.01); H03M 13/11 (2013.01); H04L 1/203 (2013.01)] | 8 Claims |

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1. A method comprising:
receiving, by a first device, a random access preamble from a second device;
transmitting, by the first device, a random access response to the second device in response to the random access preamble;
performing, by the first device, a radio resource control connection procedure with the second device;
receiving, by the first device, data from the second device;
receiving, by the first device, first two-dimensional parity information from the second device over a public channel;
obtaining, by the first device, second two-dimensional parity information from sifted key information,
wherein sifted key information comprises a plurality of first bit groups, and
wherein a length for each of the plurality of first bit groups is maximized for guaranteeing quantum bit error rate (QBER) estimation accuracy;
performing, by the first device, an estimation of a QBER based on the first two-dimensional parity information and the second two-dimensional parity information;
determining, by the first device, key information based on the estimation of the QBER; and
decrypting, by the first device, the data based on the key information.
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