Patent ID: 7080255

Claim:
A secret key generation method wherein: secret keys peculiar to entities are generated by using division vectors indicating divided specifying information resulting from division of information specifying said entities into a plurality of blocks, and personal secret random numbers peculiar to said entities, set for each of said divided blocks; said personal secret random numbers are set with different values for each component in said division vectors; said secret keys are generated using said personal secret random numbers so set and said division vectors; when number of divided blocks of said division vectors is taken as J, sizes of said division vectors as M j (j=1, 2, . . . , J), and personal secret random number for entity e as β ej (v) (v=0, 1, . . . , M j −1), where β is a random number, all J divided blocks are grouped into K groups, with one or a plurality of blocks in each group; and said secret keys satisfy γ eR1 +γ eR2 + . . . +γ eRk =nλ(N) where n is an integer, λ(.) is a Carmichael function, and N=PQ (where P and Q are prime), where: R K is a partial set of universal set U having, as members, natural numbers up to J, R p ∩R q is an empty set for any p and q, and R 1 U R 2 U . . . U R K is said universal set U; and γ eRk is a constant value obtained by calculating personal secret random numbers and correction terms in each component in division vector corresponding to S k .