Rasmussen College ASCII Encoding Excel Task

Scenario

Your software company wants to use the RSA method to both verify the user’s identity and also to send a three-letter registration message.

The company verifies the identity of the user by having the user create a three-character key from the user’s name, using the first letter of the user’s first name and the first two letters of the user’s last name. The user creates a number using the algorithm given below and sends it back to the company as an encrypted message.

The company also periodically sends release notes to the users. In order to authenticate that the notes came from the company, it sends a three-character message as a number to demonstrate that the release notes came from them.

*Note: For the purposes of this assignment, use only Latin alphabetical characters without prefixes or suffixes.

Algorithm for Encoding Letters

Use the ASCII Encoding Table to convert letters to numbers.

ASCII Encoding Table

We will represent three-character strings as a number by first finding the number for the characters, multiplying the number for the first character by 65536, and the number for the second character by 256. We then add these two products and the number for the third character to find the number that represents the string.

For example, if the characters are “GSV”, then the number associated with the characters are 71 for ‘G’, 83 for ‘S’, and 86 for ‘V’. The number associated with the string is then 71 × 65536 + 83 × 256 + 86 = 4674390.

If you have a number that represents a three-character key and want to determine what the key is,

• Step 1. Take the original number and find its modulus modulo 256 to find the number of the last character.
• Step 2. Divide the original number by 256, throwing away the remainder.
• Step 3. Take the quotient from step 2 and find its modulus modulo 256. This is the number of the middle character.
• Step 4. Divide the difference from step 4 by 256, throwing away the remainder. This is the number of the first character.

Instructions

The company chooses the prime numbers  ? and  ? to use in the RSA algorithm, and the public encryption key