1. Problem Definition In 1587, Mary, Queen of Scots, lost her head due to a scrap of paper. Fifty-five years later, Sir John Trevanion, a supporter of another beheaded monarch, Charles the First, had his head saved by a scrap of paper. What made the difference? Steganography. Sir John, a distinguished cavalier who aided Charles I against Oliver Cromwell in the English Civil War, was captured and imprisoned in Colchester Castle. The day before his execution, he received a letter from one of his friends. The letter was not smuggled in but delivered straight into the hands of his jailors, who examined it but didnt notice any deception. After reading it, Sir John asked for some time alone to pray in the chapel. When his jailors came back to fetch him, he had vanished. What was the message that was passed to Sir John to save his life? Here is the message Sir John received: Worthie Sir John: Hope, that is the beste comfort of the afflicted, cannot much, I fear me, help you now. That I would saye to you, is this only: if ever I may be able to requite that I do owe you, stand not upon asking me. 'Tis not much I can do: but what I can do, bee you verie sure I wille. I knowe that, if deathe comes, if ordinary men fear it, it frights not you, accounting for it for a high honour, to have such a rewarde of your loyalty. Pray yet that you may be spared this soe bitter, cup. I fear not that you will grudge any sufferings; onlie if bie submission you can turn them away, 'tis the part of a wise man. Tell me, an if you can, to do for you anythinge that you wolde have done. The general goes back on Wednesday. Restinge your servant to command. R.T. As you have probably guessed, this seemingly innocent letter contains a hidden message, revealed below in bold: Worthie Sir John: Hope, that is the beste comfort of the afflicted, cannot much, I fear me, help you now. That I would saye to you, is this only: if ever I may be able to requite that I do owe you, stand not upon asking me. 'Tis not much I can do: but what I can do, bee you verie sure I wille. I knowe that, if deathe comes, if ordinary men fear it, it frights not you, accounting for it for a high honour, to have such a rewarde of your loyalty. Pray yet that you may be spared this soe bitter, cup. I fear not that you will grudge any sufferings; onlie if bie submission you can turn them away, 'tis the part of a wise man. Tell me, an if you can, to do for you anythinge that you wolde have done. The general goes back on Wednesday. Restinge your servant to command. R.T. This null cipher uses every third letter after a punctuation mark to let Sir John know that a panel at east end of chapel slides. Its rumored that the remains of a narrow stairway were later discovered in a recess in a wall in the castle. The passage was blocked at the time of discovery, but it may have been Sir Johns escape route around 1642.

2. Assignment Requirements

Write Python code that finds the letters hidden after punctuation marks in a null cipher and lets the user choose the number of letters after a punctuation mark to search for a solution. Three methods are expected in the program:

o load_text(filename): returns the file content,

o solve_null_cipher(message, numberOfLetters): does not return anything, but prints the hidden message characters as shown in the expected output below o

main(): No return

Read the message from the file given in the assignment page. (trevonian.txt)

Ask user to choose the number of letters after a punctuation mark to discover the hidden message.

Use string library to detect the punctuations.

Print the characters after a punctuation mark till the user anticipated number.

Check file exceptions

3. Expected Output Given the input file: trevonian.txt, here is the expected output from your program. Be careful about the conventions in the output, you are expected to print out in the same format: Enter full filename for message to translate: trevanion.txt

ORIGINAL MESSAGE =

Worthie Sir John: Hope, that is the beste comfort of the afflicted, cannot much, I fear me, help you now. That I would saye to you, is this only: if ever I may be able to requite that I do owe you, stand not upon asking me. 'Tis not much I can do: but what I can do, bee you verie sure I wille. I knowe that, if deathe comes, if ordinary men fear it, it frights not you, accounting for it for a high honour, to have such a rewarde of your loyalty. Pray yet that you may be spared this soe bitter, cup. I fear not that you will grudge any sufferings; onlie if bie submission you can turn them away, 'tis the part of a wise man. Tell me, an if you can, to do for you anythinge that you wolde have done. The general goes back on Wednesday. Restinge your servant to command. R.T.

List of punctuation marks to check = !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~

Number of letters to check after punctuation mark: 3

Using offset of 1 after punctuation = HtcIhTiisTbbIiiiatPcIotTatTRRT

Using offset of 2 after punctuation = ohafehsftiuekfftcorufnienohe

Using offset of 3 after punctuation = panelateastendofchapelslides