IT 6823 Information Security Concept and Administration

Homework#2, Points: 100

1. Write a program in any language you like (Java, C, PHP, Python) to implement Vigenere Ciphering and deciphering schemes. [50 points]

The Vignere cipher uses a pass phrase to encrypt and decrypt. For example, to encrypt hello world with a pass phrase seal, the pass phrase is repeated over and over again in order to align with the whole plain text. The letter from the pass phrase marks the row and the letter from the plain text marks the column. The encrypted letter is found based on row and column numbers from the following Figure 1.

An example of encryption step is shown below.

To decrypt, we would reverse the process. Use the same pass phrase seal repeatedly with the encrypted text. This time, the letter from the pass phrase marks the column and the letter from the encrypted text marks the row. An example of decryption step is shown below.

A sample snapshot of your programs output should look as follows:

2. Write a program that ciphers a plain text message using double transposition scheme and vice versa. [50 points]

The program should accept five tuples of input: plain text, row, column, permutation of row and columns. An example of encrypted text for the plain text attack at dawn is shown below.

Similarly, your program should decrypt the encrypted text given the encrypted text, matrix row and column sizes, row and column permutation order. An example snapshot of output is shown below: