9 Questions on Encoding and Decoding Messages - Homework 11 | MATH 181, Assignments of Mathematics

Download 9 Questions on Encoding and Decoding Messages - Homework 11 | MATH 181 and more Assignments Mathematics in PDF only on Docsity! Math 181, Homework 11 1. Encode the message YOU SHOULD STAY using the affine cipher C = (5P+14) mod 26. 2. Decode the message VLPXV FULF which was encoded using the affine cipher C = (3P + 11) mod 26. 3. Suppose you need a cipher for encoding messages that include numbers, words and blank spaces. That is, you need to be able to encode the following characters: 26 letters, 10 digits and 1 additional character (blank space). (a) Explain how you could adapt the affine cipher we used for letters to get a cipher for doing this. (b) Are there any conditions that a and b should satisfy in order for this cipher to work? (If you don’t know what I am talking about, see the discussion about affine cipher for letters. Find out what conditions we placed on a and b there, and why we did that, and modify this to fit our purpose). 4. Encode the message PLEASE CALL using the Hill cipher C1 = (21P1 + 8P2) mod 26, C2 = (1P1 + 3P2) mod 26. Use the letter X as a dummy letter in the last block if necessary. 5. Decode the message VW ED BC QJ, which was encoded using the given Hill cipher (for two-letter blocks) C1 = (1P1 + 17P2) mod 26, C2 = (4P1 + 9P2) mod 26. 6. Encode the message GET BACK using three-digit blocks and the RSA public key system, where the message is being sent to a person with the public key (7,5459).