| CPC G09C 1/00 (2013.01) | 7 Claims |

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1. A secure PageRank computation system comprising a plurality of secure computation apparatuses,
each secure computation apparatus comprises:
a PageRank storage which stores ciphertexts of PageRanks of a plurality of transaction entities;
a transaction rate receiving circuitry which receives a ciphertext of a transaction rate from each of a plurality of data sources; and
a PageRank calculating circuitry which securely calculates, using a ciphertext of a transaction rate related to a computational objective transaction entity and a ciphertext of PageRank of a transaction counterpart that is a transaction entity having performed a transaction with the computational objective transaction entity, a ciphertext to become PageRank of the computational objective transaction entity when the ciphertext is decrypted,
wherein the transaction rate represents, for each combination of the transaction entities, a ratio of a transaction performed by the combination of transaction entities to an entire transaction history held by the data sources.
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