Pseudo Code for Decoding a Message Using the Ubchi Cipher Method

Overview

The task involves decoding a given string using the Ubchi cipher method with a specified key. This pseudo code outlines the necessary steps to achieve this.

Inputs

• encoded_message: The string to be decoded (e.g., "notti vgfstrermasee eaien ur o peuitrnoa msz veadstI").
• key: The cipher key used for decoding (e.g., "Cipher").

Steps

1. Initialize Variables

   • Set encoded_message to the input string.
   • Set key to the provided key.
   • Create an empty string decoded_message to store the result.

2. Preprocess Key

   • Calculate the length of the key and store it in a variable key_length.
   • Create a mapping from the characters of the key to their respective positions.

3. Decoding Loop

   • For each character index i in the encoded_message:
     • Get the current character current_char.
     • Compute the shift based on the corresponding character in the key:
       • Let shift equal (position_of_key_character - ASCII value of 'a').
     • Determine if current_char is a letter:
       • If it is a letter:
         • If current_char is uppercase:
           • Calculate the new character index using the formula:
             • new_index = (ASCII value of current_char - ASCII value of 'A' - shift + 26) % 26 + ASCII value of 'A'
         • Else (if current_char is lowercase):
           • Calculate the new character index using the formula:
             • new_index = (ASCII value of current_char - ASCII value of 'a' - shift + 26) % 26 + ASCII value of 'a'
         • Append the resulting character (new_index) to decoded_message.
       • Else (if current_char is not a letter):
         • Append current_char directly to decoded_message.

4. Output Result

   • Return the decoded_message.

Pseudo Code

FUNCTION decodeUbchi(encoded_message, key):
    SET decoded_message = ""

    // Preprocess the key
    SET key_length = LENGTH(key)
    
    // Loop through each character in the encoded message
    FOR i FROM 0 TO LENGTH(encoded_message) - 1:
        SET current_char = encoded_message[i]
        
        // Get the character from key
        SET key_character = key[i % key_length]
        SET shift = ASCII(key_character) - ASCII('a') // Compute shift for lowercase
        
        // Check if current_char is a letter
        IF current_char IS LETTER THEN:
            IF current_char IS UPPERCASE THEN:
                SET new_index = (ASCII(current_char) - ASCII('A') - shift + 26) % 26 + ASCII('A')
            ELSE:
                SET new_index = (ASCII(current_char) - ASCII('a') - shift + 26) % 26 + ASCII('a')
                
            // Append the decoded character
            SET decoded_message = decoded_message + CHARACTER(new_index)
        ELSE:
            // If not a letter, append as is
            SET decoded_message = decoded_message + current_char

    RETURN decoded_message

Conclusion

This pseudo code outlines the logic and steps necessary to decode the encoded message using the Ubchi cipher method with the provided key. It handles both upper and lowercase letters while maintaining non-letter characters in their original form.