Data transmitter and data receiver

A data receiving apparatus for receiving information data encrypted by using predetermined key information and performing secret communication with a transmitting apparatus, the data receiving apparatus comprising:

• a multi-level code generation section for generating, based on the predetermined key information, a multi-level code sequence in which a signal level changes so as to be approximately random numbers;
• a demodulator section for demodulating, in a predetermined demodulation method, a modulated signal received from the transmitting apparatus so as to be outputted as a multi-level signal having a plurality of levels corresponding to a combination of the information data and the multi-level code sequence;
• and
• an identification section for identifying, based on the multi-level code sequence, the information data from the multi-level signal, wherein
• the multi-level code generation section generates the multi-level code sequence in accordance with a changed random number sequence which results from changing a bit series of a binary random number sequence generated based on the predetermined key information.

A data transmitting method for encrypting information data by using predetermined key information and performing secret communication with a receiving apparatus, the data transmitting method comprising:

• a multi-level code generating step of generating, based on the predetermined key information, a multi-level code sequence in which a signal level changes so as to be approximately random numbers;
• a multi-level processing step of combining the multi-level code sequence and the information data and generating a multi-level signal having a plurality of levels corresponding to a combination of the multi-level code sequence and the information data;
• and
• a modulating step of generating a modulated signal by treating the multi-level signal with predetermined modulating processing, wherein
• the multi-level code generation step generates the multi-level code sequence in accordance with a changed random number sequence which results from changing a bit series of a binary random number sequence generated based on the predetermined key information.

A data receiving method for receiving information data encrypted by using predetermined key information and performing secret communication with a transmitting apparatus, the data receiving method comprising:

• a multi-level code generating step of generating, based on the predetermined key information, a multi-level code sequence in which a signal level changes so as to be approximately random numbers;
• a demodulating step of demodulating, in a predetermined demodulation method, a modulated signal received from the transmitting apparatus so as to be outputted as a multi-level signal having a plurality of levels corresponding to a combination of the information data and the multi-level code sequence;
• and
• an identification step of identifying, based on the multi-level code sequence, the information data from the multi-level signal, wherein
• the multi-level code generation section generates the multi-level code sequence in accordance with a changed random number sequence which results from changing a bit series of a binary random number sequence generated based on the predetermined key information.