| 摘要 |
PROBLEM TO BE SOLVED: To improve security against an attack from a third party for the sharing of secret information while maintaining convenience in use. SOLUTION: First, in a security instrument 10, a shared matrixαEM (the character E in the shared matrixαEM is a substitute for a character that cannot be inputted indicating thatαbelonging to a set M is an element or a factor of M) is generated and sent to a security instrument 30. In the security instrument 10, natural numbers n<SB>A</SB>and r<SB>A</SB>which are secret information are set, and K<SB>A</SB>=S(r<SB>A</SB>)×α<SP>nA</SP>×S(r<SB>A</SB>)<SP>-1</SP>is calculated and sent to the security instrument 30. S(r) is a reversible commutative matrix. In the security instrument 30, natural numbers n<SB>B</SB>and r<SB>B</SB>which are secret information are set, and K<SB>B</SB>=S(r<SB>B</SB>)×α<SP>nB</SP>×S(r<SB>B</SB>)<SP>-1</SP>is calculated and sent to the security instrument 10. In the security instrument 10, K<SB>AB</SB>=S(r<SB>A</SB>)×K<SB>B</SB><SP>nA</SP>×S(r<SB>A</SB>)<SP>-1</SP>is calculated and in the security instrument 30, K<SB>AB</SB>=S(r<SB>B</SB>)×K<SB>A</SB><SP>nB</SP>×S(r<SB>B</SB>)<SP>-1</SP>is calculated to share the common secret information K<SB>AB</SB>. COPYRIGHT: (C)2005,JPO&NCIPI
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