assign1 -SDES - SCSR 3443 INTRODUCTION TO CRYPTOGRAPHY...

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SCSR 3443 INTRODUCTION TO CRYPTOGRAPHY ASSIGNMENT 1 Assignment Rules: Every student must follow all rules. Marks will be deducted for submissions after the deadline. Preparing assignments independently is a key factor for understanding the class material. Therefore it is highly recommended every student make a serious effort to solve the problems on their own. Any cases of plagiarism will be dealt severely. (For example, reducing grades for the whole course, not just the relevant assignment, and/or reporting the incident to the appropriate university authority.) If we suspect Mary had copied from John, both party will be regarded as cheaters. In order not to lead to any suspicious ideas by the lecturer, make sure the write-up and data used is unique. Dateline for Assignment 1 is: Instructions: A. Simplified DES (S-DES) has similar properties and structure to DES but with much smaller parameters. The aim of this assignment is for the student to practically go through the process of encryption as well as decryption of S-DES and indirectly will help in understanding the working of DES. B. Each student must read the S-DES structure for key generation and encryption. Each group will create a plaintext message and key as follow: i. Create Message Select a group member’s birthday: _________________ (DD/MM) where DD 16 Convert DD to a 4-bit binary number: Convert MM to a 4-bit binary number: Combine DD-MM to form a 8-bit message, M :
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ii. Generate Key Select a group member’s birthday: _________________ (DD/MM) Convert DD to a 5-bit binary number: Convert MM to a 5-bit binary number: Combine DD-MM to form a 10-bit key, K : Note : The values must not be the same as in the literature. C. Write a report documenting every step of the encryption and decryption process as well as key generation. This includes stating the input and output for every P-Boxes and S-Boxes. D. Once all the values have been obtained, summarized your result in the following Figure 1 and Figure 2 and combine this Figure with the report of (C).
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Summarized of Encryption Process Figure 1 Encryption Process
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Summarized of Decryption Process Figure 2. Decryption Process
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8/5/05 C-2 Simplified DES, developed by Professor Edward Schaefer of Santa Clara University [SCHA96], is an educational rather than a secure encryption algorithm. It has similar properties and structure to DES with much smaller parameters. The reader might find it useful to work through an example by hand while following the discussion in this Appendix. C.1 Overview Figure C.1 illustrates the overall structure of the simplified DES, which we will refer to as S- DES. The S-DES encryption algorithm takes an 8-bit block of plaintext (example: 10111101) and a 10-bit key as input and produces an 8-bit block of ciphertext as output. The S-DES decryption algorithm takes an 8-bit block of ciphertext and the same 10-bit key used to produce that ciphertext as input and produces the original 8-bit block of plaintext.
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