Patent ID: 7711962

Claim:
A data-transmission system that sends transmission data, which has been encrypted by using at least one conversion constant from among a first conversion constant, a second conversion constant, and a third conversion constant, from an apparatus on a sending side to an apparatus on a receiving side, wherein said apparatus on the sending side comprises: a conversion-constant selection means for selecting said first conversion constant, said second conversion constant, and said third conversion constant; an encryption means for using said second conversion constant, or said second conversion constant and said third conversion constant, to encrypt said transmission data to a first substitute value, and for using said first conversion constant, or said first conversion constant and said third conversion constant, to encrypt said transmission data to a second substitute value; a first-signal-generation means for generating a first signal that contains said first substitute value and said first conversion constant; a memory means for storing a pattern-conversion constant that corresponds to said third conversion constant; a second-signal-generation means for generating a second signal that contains said second substitute value, said second conversion constant and said pattern-conversion constant; and a transmission means for sending said first signal to said apparatus on the receiving side and for sending said second signal to a relay apparatus; said relay apparatus comprises: a memory means for storing said third conversion constant that corresponds to said pattern-conversion constant; a signal-generation means for receiving said second signal, and for converting said pattern-conversion constant contained in said second signal to said third conversion constant to generate a third (second′) signal; and a transmission means for sending said third signal to said apparatus on the receiving side; and said apparatus on the receiving side comprises: a reading means for receiving said first signal from said apparatus on the sending side and said third signal from said relay apparatus, and for reading said first substitute value and said first conversion constant from said first signal, and for reading said second substitute value, said second conversion constant and said third conversion constant from said third signal; a decoding means for using said conversion constants that were used in encrypting said first substitute value and said second substitute value to decode said first substitute value and said second substitute value to first decoded data and second decoded data, respectively; and an authentication means for authenticating said first signal and said third signal from said first decoded data and said second decoded data.