Use the histograms from Exercise 7.3 to create a mapping where all letters occur with the same frequency. Write a program that uses this mapping to encode and decode text. Verify that the program works. Compare the size of the plaintext and ciphertext.

Repeat Exercise 7.6 but use histograms of letter sequences from Exercise 7.4.

Exercise 7.4

Write a program to create histograms involving the usage frequency of sequences of letters and punctuation marks. The program should accept as input the sequence length. Use the program to create histograms from the same text files as Exercise 7.3. Compare the histograms.

Exercise 7.6

Use the histograms from Exercise 7.3 to create a mapping where all letters occur with the same frequency. Write a program that uses this mapping to encode and decode text. Verify that the program works. Compare the size of the plaintext and ciphertext.