| 摘要 |
PURPOSE: To extend normal sentence bit length/ciphered bit length and to efficiently cipher a disclosed key by requiring a secret key selecting method for a quardratic equation cipher. CONSTITUTION: A prime number generating part K11 outputs a prime number (p) less than (m-2) /m×N} bits (provided that N is a natural number and (m) is a rational number of>2) and a prime number (q) consisting of (N-2p) bits and an (n) generation part K12 calculates p<2> q and outputs a natural number (n) consisting of N bits. On the other hand, a (v) generation part K13 generates a natural number (v) from the values (p), (q) and an (a) generation part K15 generates a natural number (a) smaller than (1/2)v<1/2> . A (b) generation part K15 selects a natural number (b) smaller than the natural number (p) and a (u) generation part K16 generates a natural number (u) front (a + bv). When the natural numbers (n). (u) are set up as disclosed keys and the natural numbers (p), (q), (v), (a), (b) are set up secret keys, the number of bits in a normal sentence corresponding to an N-bit ciphered sentence is N/ (m-1)} bits, normal sentence bit length/ciphered bit length is extended in accordance with the selection of the rational number (m) and disclosed key ciphering utilizing the quardratic equation can be efficiently executed. |
