Patent ID: 7822204

Claim:
An encryption method comprising: modulating input data into a multilevel signal by associating the data with one set of a plurality of sets of pairs of states by a pseudo random number; providing an irregular association to the multilevel signal by modulating the multilevel signal by associating the multilevel signal with a discrete value determined by a physical random number so that the modulated multilevel signal belongs to either a first range which is determined by said pseudo random number when a state of said input data is one state of each pair of states, or a second range which is determined by said pseudo random number when said state of said input data is the other state of each pair of states and which does not overlap said first range to be exclusive to said first range, the irregular association being provided to the multilevel signal by adding/subtracting the output value of said physical random number to/from the multilevel signal; and channel-coding the modulated multilevel signal, to which the irregular association is provided, into a desired coded word and outputting the coded word as encrypted data, wherein: the decoded signal obtained by channel-decoding said encrypted data is demodulated into said input data by determining whether the decoded signal belongs to said first range or said second range based on a demodulation pseudo random number and associating the decoded signal with either state of each pair of states based on the determined range and said demodulation pseudo random number.