Problems
88. Caesar cipher
Write a program that can encrypt and decrypt messages using a Caesar cipher with a right rotation and any shift value. For simplicity, the program should consider only uppercase text messages and only encode letters, ignoring digits, symbols, and other types of characters.
89. Vigenère cipher
Write a program that can encrypt and decrypt messages using the Vigenère cipher. For simplicity, the input plain-text messages for encryption should consist of only uppercase letters.
90. Base64 encoding and decoding
Write a program that can encode and decode binary data using the base64 encoding scheme. You must implement the encoding and decoding functions yourself and not use a 3rd party library. The table used for encoding should be the one from the MIME specification.
91. Validating user credentials
Write a program that simulates the way users authenticate to a secured system. In order to log in, a user must be already registered with the system. The user enters a username and...
