| CPC H04L 9/0866 (2013.01) [H04L 9/14 (2013.01); H04L 9/3093 (2013.01)] | 19 Claims |

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1. A functional encryption system, comprising:
a key generation device configured to generate a public key and a secret key, based on a master key and a parameter vector;
an encryption device configured to generate encrypted data by encrypting an input vector, based on the public key; and
a decryption device configured to generate decrypted data that is an approximation value of an inner product of the parameter vector and the input vector by decrypting the encrypted data based on the secret key,
wherein the approximation value of the inner product includes an inner product error value corresponding to a difference between the decrypted data and the inner product,
wherein the key generation device is further configured to generate an encrypted parameter vector including an amplified parameter vector corresponding to a multiplication of the parameter vector and an error factor value, and
wherein when the decryption device generates the decrypted data, the inner product error value is decreased as the error factor value is increased.
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