| 摘要 |
PROBLEM TO BE SOLVED: To provide a content distribution system for suppressing the data quantity of a secret key while maintaining safety. SOLUTION: In a content distribution system 1, an encryption information generation device 10 is configured to generate two prime numbers and generation origin as basic information, and to generate the coefficients of the first polynomial and the second polynomial using numbers k<SB>1</SB>and k<SB>2</SB>which are equal to or more than the maximum coalition persons k as degrees, and to calculate a powered value calculated by powering generation origin g by the coefficients of the first polynomial and a powered value calculated by powering generation origin h by the coefficients of the second polynomial, and to generate a public key including a multiplied powered value calculated by multiplying k<SB>3</SB>pieces of powered values corresponding to coefficients with at least degrees calculated by subtracting k<SB>3</SB>(1≤k<SB>3</SB>≤k<SB>1</SB>-k+1 and k<SB>3</SB>≤k<SB>2</SB>-k+1) from the maximum degree k<SB>1</SB>of the first polynomial by k<SB>3</SB>pieces of powered values counted from the coefficients with the minimum degree of the second polynomial and any powered value group other than the powered values used for the arithmetic operation of the multiplied powered value and the basic information. COPYRIGHT: (C)2009,JPO&INPIT
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