CS3626Sp2024_HW05

- 1 - CS3626 Homework 03 Spring 2024 DES Total Points: 25 Be as brief as possible and use your own words when describing concepts.   SHOW ALL WORK for Questions requiring calculations and algorithms. Q-1: Given the following initial key: K = { 47 72 65 79 48 61 74 20 4F 70 23 33 31 20 42 65 } these values are hex. What are the values of W 00 , W 01 , W 02 and W 03 ? 1 points Calculate W 04 and W 05 show the steps (if necessary) of the key generating auxiliary function. 2 points Q-2: For the decryption inverse mix columns calculation shown above, given the input matrix: S 00 S 01 S 02 S 03 0x33 0x21 0x3E 0xFC S 10 S 11 S 12 S 13 0x45 0x8A 0x72 0x92 S 20 S 21 S 22 S 23 = 0x00 0xDE 0x0E 0x49 S 30 S 31 S 32 S 33 0x22 0xBB 0xFE 0X0F EXAMPLE: To calculate S 00 the polynomial shortcut equation is determined as: 0E*0x33 ⊕ 0B*0x45 ⊕ 0D*00 ⊕ 09*22

- 2 - To calculate 0E * 0x33 = (x 3 + x 2 + x 1 ) * (x 5 + x 4 + x 1 + x 0 ) = (x 8 + x 7 + x 4 + x 3 ) ⊕ (x 7 + x 6 + x 3 + x 2 ) ⊕ (x 6 + x 5 + x 2 + x 1 ) But this result has an x 8 or greater degree so we need perform a mod by m(X) as well: (x8 + x4 + x3 + x1 + x0) However, degree is only x 8 , we can just XOR m(x) as a shortcut so the polynomial equation for 0x0E*0x33 ⊕ m(x) is: (x 8 + x 7 + x 4 + x 3 ) + (x 7 + x 6 + x 3 + x 2 ) + (x 6 + x 5 + x 2 + x 1 ) + (x 8 + x 4 + x 3 + x 1 + x 0 ) Polynomial Equation Result = x 5 + x 3 + x 0 Determine the polynomial equation for S 33 . Did it require either of including XOR m(x) term or a long division modulo with m(x)? 2 points Q-3: What is the definition of a nonce? 1 point Q-4: What security vulnerability is present when using Electronic Codebook encryption for long messages. 1 point

- 4 - 1 point Q-11: divide_galois will return the value of r, however q is needed as well, modify divide_galois to return both remainder and quotient: Depending on your language, you may return it as a structure, array or some other poly-value or you can call by reference for example: unsigned int divide_galois( A(x), m(x)) becomes void divide_galois( A(x), m(x), &r, &q) where &r,&q are call-by-reference. 5 points

- 5 - Submission Guidelines:  No handwritten submission is accepted, always submit answers as text within this or similar document file with any support images embedded in the file.  EXCEPTION : If asked for source code implementation you can submit those individually and as separate files in ASCII format in their original file format .cpp, .java, .py, .cs etc. or even as a .txt file will be acceptable. Do not insert code into the submission document file. It ruins spacing which makes .python and some languages (perl, awk etc.) difficult to test build.  Do not submit ZIP files… ever… for anything in D2L. The system is extremely unhelpful with regards to those filetypes and grading.  You may include your freehand drawing/image and handwritten scans in the submission. However, the writing and images must be clearly legible. Though, it is best to present non-handwritten submissions, generally, as is done in the professional setting.  If asked, show all work/calculations/graphs etc. in the determination of the problem.  Please complete your entire work in a single Word Document and Save the file as: yournetid_CS3502_Assignment01.docx (e.g. ogarcia5_CS3502_Assignment01.docx.) and upload your file in D2L.  Please observe the submission due date and time. After the due date there is a 50% penalty for the next 24 hours. Any submission after 24 hours of the due date will be graded at 0%.  If you include a reference or an image taken from other sources, please cite them appropriately. APA is preferred but cite them so they can be found. NOTE: verbatim copying or even paraphrasing is plagiarism so if the source used constitutes your answer rather than simply supporting the answer, it will be considered invalid. This is especially true of source code implementation answers.  If you resubmit, please make sure to attach the file again. Your latest submission before the due date will be the one graded.