Abstract: Provided are a data transmitting apparatus and a data receiving apparatus which use a Y-00 protocol and are capable of preventing an eavesdropper's decryption based on a transition pattern of a multi-level signal level. The data transmitting apparatus 101,103 of the present invention includes: a multi-level code generation section 111 for generating, by using predetermined key information 11, a multi-level code sequence 12 in which a value changes so as to be approximately random numbers; and a multi-level signal modulator section 112,125 for generating a converted multi-level signal 23 in accordance with information shared with the receiving apparatus 201,203, the multi-level code sequence 12 and information data 10, modulating the converted multi-level signal 23 in a predetermined modulation method, and outputting a resultant modulated signal 14. The converted multi-level signal 23 is a signal having a plurality of signal point allocations which are different from one another.

Abstract: A data communication apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. A multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which signal in which a signal level changes so as to be approximately random numbers. A multi-level processing section 112 combines information data 10 and the multi-level code sequence 12, and generates a multi-level signal 13 having a plurality of levels each corresponding to the combination of the information data 10 and the multi-level code sequence 12. A delayed wave generation section 113 generates, based on a delay profile 19, a delayed wave of the multi-level signal 13, combines the generated delayed wave and the multi-level signal 13, and outputs a multipath signal 20. A modulator section 114 modulates the multipath signal 20 in a predetermined modulation method, and outputs a modulated signal 14.

Abstract: A data transmitting apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. The multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. The multi-level processing section 112 generates a multi-level signal 13 having a level which corresponds to a combination between information data 10 and the multi-level code sequence 12. The error signal generation section 113 generates an error signal 21 which changes randomly. The accumulation section 114 accumulates the error signal 21, and outputs an accumulated error signal 22. The adding section 116 adds the accumulated error signal 22 to the multi-level signal 13, and outputs a variable multi-level signal 23. The modulator section 117 modulates the variable multi-level signal 23, and outputs a modulated signal 14.

Abstract: A data communication apparatus which improves security against eavesdropping is provided for secret communication using Y-00 protocol. A multi-level code generation section 111 generates, based on key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. A level conversion section 113 irreversibly converts the multi-level code sequence 12 such that a converted multi-level code sequence 19 does not constitute a mapping of the multi-level code sequence 12. A multi-level processing section 112 generates a multi-level signal 13 having a plurality of levels each corresponding to a combination between the information data 10 and the multi-level code sequence 12. A modulator section 114 modulates a multi-level signal 14 in a predetermined modulation method and outputs a modulated signal 15.

Abstract: A data communication apparatus which causes the eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability is provided. In a modulator section 112a, a branching section 114 branches a lightwave 20 outputted from a light source 113, and outputs respective branched lights to a first light path 117 and a second light path 118 respectively having different light path lengths. A light modulator section 116 modulates, based on a multi-level signal 13, a lightwave propagating at least one light path of the first light path 117 and the second light path 118. An interference section 119 causes the lightwaves outputted from the first light path 117 and the second light path 118 to interfere with each other, and outputs such interfered lightwave as a modulated signal 14.

Abstract: A highly concealable data communication apparatus which is based on an astronomical complexity and causes an eavesdropper to take a significantly increased time to analyze a cipher text, is provided. In a multi-level code generation section 111a, a random number sequence generation section 141 generates, based on predetermined key information 11, a plurality of modulation pseudo-random number sequences. The plurality of modulation pseudo-random number sequences is inputted to a multi-level conversion section 142 as a part of an input bit sequence which is converted into a multi-level code sequence 12. A multi-level processing section 111b combines the multi-level code sequence 12 and information data 10, and generates a multi-level signal 13 having a plurality of levels corresponding to a combination of the multi-level code sequence 12 and the information data 10.

Abstract: A data transmitting apparatus 1101 generates, by using predetermined first key information 11; and information data 10, a multi-level signal 13 in which a signal level changes so as to be approximately random numbers, and converts the multi-level signal 13 into a modulated signal 14, in a predetermined modulation method and transfer the same. A data receiving apparatus 1201 demodulates the modulated signal 14 so as to be converted into a multi-level signal 15, and reproduces information data 18 from the multi-level signal 15, using second key information 16 which has the same content as first key information 11 used by the data transmitting apparatus 1101.

Abstract: A data communication apparatus which causes the eavesdropper to take a significantly increased time to analyze a cipher text and provides high concealability is provided. A multi-level code generation section 111a generates, based on predetermined key information 11, a multi-level code sequence 12 in which a signal level changes so as to be approximately random numbers. A multi-level processing section 111b combines the multi-level code sequence 12 and information data 10, and generates a multi-level signal 13 having a plurality of levels corresponding to the combination of the multi-level code sequence 12 and the information data 10. A modulator section 112 treats the multi-level signal a predetermined modulating processing and generates a modulated signal.

Abstract: A data communication apparatus 1 for safely transmitting information data 11 and additional information 14 is provided. In a data transmitting apparatus 101, a random number sequence generating part 111 generates a random number sequence 12 from key information 11. A diffusing part 112 generates diffused additional information 14 by time-diffusing additional information 14. A multi-level signal generating part 113 generates a multi-level signal 16 the signal level of which varies substantially like a random number, based on information data 13, the random number sequence 12, and the diffused additional information 14. In a data receiving apparatus 201, a random number sequence generating part 211 generates a random number sequence 22 from key information 21. An information data decoding part 213 decodes information data 23 and additional information 24 based on the random number sequence 22.