Security device including physical unclonable function cells and operation method thereof

1. An operation method of a security device including a controller and a plurality of physical unclonable function (PUF) cells, the method comprising the controller:

selecting a target PUF cell from among the plurality of PUF cells;

selecting at least two reference PUF cells other than the target PUF cell from among the plurality of PUF cells based on a sorted list of the plurality of PUF cells;

reading a plurality of sensing data from the target PUF cell and the at least two reference PUF cells;

determining a target bit corresponding to the target PUF cell based on the plurality of sensing data to provide a determined target bit; and

generating a security key based on the determined target bit,

wherein the selecting of the at least two reference PUF cells comprises:

setting a window in the sorted list, the window including a physical address of the target PUF cell; and

selecting at least two PUF cells corresponding to physical addresses included in the window in the sorted list as the reference PUF cells,

wherein parameters associated with a window size, a skip size, and a window direction of the window are determined based on a logical order of the physical address of the target PUF cell in the sorted list.

2. The method of claim 1 , wherein each of the plurality of sensing data includes mismatch information corresponding to respective ones of the target PUF cell and the at least two reference PUF cells.

3. The method of claim 1 , wherein the sorted list includes information about physical addresses of the plurality of PUF cells, and

wherein a logical order of the physical addresses in the sorted list is sorted by an order of size of raw data of the plurality of PUF cells.

4. The method of claim 3 , wherein the raw data of the plurality of PUF cells are obtained in a test process or a process of manufacturing the security device.

5. The method of claim 3 , wherein physical addresses of the at least two reference PUF cells are logically adjacent to a physical address of the target PUF cell in the sorted list.

6. The method of claim 1 , wherein the plurality of PUF cells are divided into a plurality of groups based on the sorted list,

wherein, when the target PUF cell is included in a first group of the plurality of groups, a number of the at least two reference PUF cells in the first group is “n” (n being an integer of 2 or more), and

wherein, when the target PUF cell is included in a second group of the plurality of groups, a number of the at least two reference PUF cells in the first group is “m” (m being an integer more than n).

7. The method of claim 6 , wherein a reliability of PUF cells included in the first group from among the plurality of PUF cells is higher than a reliability of PUF cells included in the second group from among the plurality of PUF cells.

8. The method of claim 1 , wherein the determining of the target bit corresponding to the target PUF comprises:

generating determination data based on the plurality of sensing data; and

determining the target bit based on the determination data.

9. The method of claim 8 , wherein the determination data includes first data n times greater than sensing data having a greatest absolute value from among the plurality of sensing data, and second data that is a sum of remaining sensing data of the plurality of sensing data other than the sensing data having the greatest absolute value, wherein n is a number of the remaining sensing data, and

wherein the target bit is determined as a first value when the first data is greater than the second data, and the target bit is determined as a second value different from the first value when the first data is smaller than the second data.

10. The method of claim 1 , wherein the determining of the target bit corresponding to the target PUF cell comprises:

comparing a reference value with each of the plurality of sensing data to generate a plurality of pre-bits respectively corresponding to the plurality of sensing data; and

determining the target bit based on the plurality of pre-bits.

11. An operation method of a security device including a controller and a plurality of physical unclonable function (PUF) cells, the method comprising the controller:

reading raw data from each of the plurality of PUF cells;

generating a sorted list by sorting physical addresses respectively associated with the plurality of PUF cells in an order of size of the raw data and storing the sorted list;

selecting a target PUF cell of the plurality of PUF cells;

selecting at least two reference PUF cells corresponding to the target PUF cell based on the sorted list;

reading a plurality of sensing data from the target PUF cell and the at least two reference PUF cells;

determining a target bit corresponding to the target PUF cell based on the plurality of sensing data; and

generating a security key based on the determined target bit,

wherein the selecting of the at least two reference PUF cells comprises:

setting a window in the sorted list, the window including a physical address of the target PUF cell; and

selecting at least two PUF cells corresponding to physical addresses included in the window in the sorted list as the reference PUF cells,

wherein parameters associated with a window size, a skip size, and a window direction of the window are determined based on a logical order of the physical address of the target PUF cell in the sorted list.

12. The method of claim 11 , wherein the sorted list includes only physical addresses of the plurality of PUF cells, and

wherein the physical addresses of the plurality of PUF cells in the sorted list are sorted in an order of size of the raw data.

13. A security device comprising:

a PUF cell array including a plurality of physical unclonable function (PUF) cells; and

a controller configured to control the plurality of PUF cells,

wherein the controller comprises

a memory configured to store a sorted list including physical addresses of the plurality of PUF cells,

a window controller configured to select a target PUF cell from among the plurality of PUF cells and to select at least two reference PUF cells corresponding to the target PUF cell from among the plurality of PUF cells, based on the sorted list,

a PUF cell controller configured to control the target PUF cell and the at least two reference PUF cells,

a receiver configured to receive a plurality of sensing data from the target PUF cell and the at least two reference PUF cells, and

a bit determiner configured to receive the plurality of sensing data from the receiver and to determine a target bit corresponding to the target PUF cell based on the plurality of sensing data,

wherein the window controller is configured to select the at least two reference PUF cells by setting a window corresponding to the target PUF cell to the sorted list, and

wherein the window controller is further configured to vary a window size of the window in the sorted list depending on a logical location of a physical address of the target PUF cell.

14. The security device of claim 13 , wherein the plurality of sensing data received from the target PUF cell and the at least two reference PUF cells are analog information, and

the receiver includes an analog-to-digital converter configured to convert the analog information to digital information, and the receiver outputs the digital information to the bit determiner as the plurality of sensing data.