Take a gray-level image of 8 bit depth in pgm format (or some other simple image formatthat directly represents the gray values without complicated encoding). Take DES andencrypt the image (using ECB mode or CBC mode).a. (Brutal force attack - 25 points) Try a brutal force attack on the ciphertext. Plot therelationship between key length and time consumed for the attack. (Since keys for DESare of 56-bit, you can simulate a key of n-bit (n<56) by fixing the remaining 56-n bits.).You may want to use diff and time shell command in Unix/Linux. No need to plot for allthe key lengths, but the curve should be able to show the trend. Please submit yourcode, instruction on how to compile/run your code, the figure and explanation onthe figure.b. (Compare ECB and CBC – Bonus points: 10 points) Encrypt the image (a) usingelectronic codebook (ECB) mode, and (b) using cipher block chaining (CBC) mode.Include original, ECB and CBC mode images in your document, that is, visualize theresult of your experiment. Explain the result of your experiment in technical terms, andexplain the cryptographic relevance. (You may want to read the section on ECB and CBCin Chapter 6.2.)You can use, for example, the cryptographic library contained in openssl for thisexperiment, www.openssl.org. Incidentally, this library is interesting since it containsimplementations of all cryptographic primitives that we have discussed so far.