To make an attack algorithm concrete concerning a so-called FMK attack method conventionally proposed to the power product type ID-NIKS of a certain class, of which the sum of all components becomes a fixed value by all public keys.
A conspiracy attack is performed while utilizing the public keys of conspirators further more than irreducibly minimum conspirators. Each time one public key is acquired from one of conspirators further more than irreducibly minimum conspirators, the exchange position of the public key is determined at random and the conspiracy attack can be performed while utilizing calculations before the last time as well. Otherwise, the exchange position of the public key is selected so as to minimize a matrix formula and the conspiracy attack can be performed while utilizing calculations before the last time as well.
MURAKAMI YASUMICHI
KASAHARA MASAO
KASAHARA MASAO
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