Security device for generating masking data based on physically unclonable function and operating method thereof

A method of generating a security key by using a physically unclonable function (PUF) circuit including a plurality of PUF cells, the method comprising:

• generating random key data by using a set of first PUF cells including at least one first PUF cell included in the PUF circuit;
• generating a key through post-processing performed on the random key data;
• generating masking data by using a set of second PUF cells including at least one second PUF cell included in the PUF circuit;
• masking the key by using the masking data to generate a masked key;
• and
• storing the masked key in a key buffer.

A security device comprising:

• a physically unclonable function (PUF) block including a plurality of PUF cells outputting random key data and masking data;
• a validity detector configured to determine the validity or not of the plurality of PUF cells and to generate a validity map on the basis of a result of the determination;
• a key generator configured to generate a key through post-processing performed on the random key data;
• and
• a masking module configured to mask and store the key by using the masking data,
• wherein the PUF block is configured to generate the masking data on the basis of the validity map.