Image sensor, image processing system having the same and operating method of the same
An image sensor includes a non-volatile memory (NVM) storing a encoded private key and partial information of a private key, using first random numbers generated by repeating a first random number generation operation using the partial information of the private key, and a security circuit that performs a decryption operation on a cipher text received from a controller. The security circuit includes a self-recursive decoder that receives the encoded private key from the NVM during the decryption operation, repeats a second random number generation operation using the partial information of the private key to generate second random numbers, and uses the second random numbers to restore the encoded private key to the private key, and a crypto module that uses the restored private key to decrypt the cipher text.
1. An image sensor comprising:
an image sensing circuit configured to acquire image data; and
a security circuit configured to generate a tag for integrity of the image data,
wherein the security circuit includes:
a crypto circuitry configured to receive a cipher text that is encrypted with a public key from a controller, and decrypt the cipher text based on an encryption algorithm using a private key; and
a differential power analysis (DPA) countermeasure circuitry configured to perform DPA defense against an operation of the crypto circuitry using a random value corresponding to all or a portion of the cipher text.
2. The image sensor of claim 1 , wherein the security circuit performs an authentication operation with the controller.
3. The image sensor of claim 1 , wherein the security circuit further comprises:
random number generator circuitry configured to generate a random number using the random value; and
an entropy spreader circuitry configured to output an index corresponding to the random value to increase randomness of the cipher text.
4. The image sensor of claim 3 , wherein the cipher text is divided into a plurality of divided data,
wherein the random number generator circuitry determines one of the plurality of divided data as the random number according to the index.
5. The image sensor of claim 4 , wherein the random number generator circuitry comprises a multiplexer configured to select one of the plurality of divided data according to the index.
6. The image sensor of claim 5 , wherein the index is a value corresponding to temperature information of the image sensing circuit.
7. The image sensor of claim 5 , wherein the entropy spreader circuitry comprises:
a temperature sensor configured to sense a temperature of the image sensing circuit and output temperature information based on the temperature; and
index encoder circuitry configured to output the index using the temperature information.
8. The image sensor of claim 5 , wherein the entropy spreader circuitry is implemented with a block cipher-based pseudo-random number generator (BPRNG).
9. The image sensor of claim 5 , wherein the entropy spreader circuitry generates the index using the cipher text and the encryption algorithm.
10. The image sensor of claim 1 , wherein the encryption algorithm is an asymmetric-key encryption algorithm.
11. An operating method of an image sensor, the operating method comprising:
receiving a cipher text from a controller;
generating a random number using the cipher text; and
executing a differential power analysis (DPA) countermeasure module using the random number,
wherein the generating the random number comprises:
dividing the cipher text into a plurality of divided data; and
selecting one of the plurality of divided data as the random number according to an index.
12. The operating method of claim 11 , wherein the cipher text is encrypted with a public key of the image sensor.
13. The operating method of claim 12 , further comprising transmitting the public key to the controller.
14. The operating method of claim 11 , wherein the generating the random number further comprises generating the index using a pseudo-random number generator.
15. An image processing system comprising:
an image sensor configured to acquire image data; and
a controller configured to receive the image data from the image sensor,
wherein the image sensor includes:
an image sensing circuit configured to sense the image data; and
a security circuit configured to perform an authentication operation with the controller, to receive a cipher text from the controller, and to decrypt the received cipher text using a secret key,
wherein the security circuit generates a random number using all or a portion of the cipher text, and prevents a differential power analysis (DPA) attack on the secret key in a decryption operation of the cipher text using the random number.
16. The image processing system of claim 15 , wherein the security circuit generates a tag corresponding to the image data, and
the image sensor transmits the image data and the tag to the controller through a first communication channel and receives the cipher text through a second communication channel.
17. The image processing system of claim 16 , wherein the first communication channel communicates in a camera serial interface (CSI) mode, and
the second communication channel communicates in an inter-integrated circuit (I2C) mode.
18. The image processing system of claim 15 , wherein the security circuit comprises random number generator circuitry configured to receive the cipher text and to generate the random number using the cipher text.
19. The image processing system of claim 18 , wherein the security circuit further comprises an entropy spreader circuitry configured to output a random value for increasing randomness of the cipher text using internal information of the image sensor.