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CSS220_Module4_Homework1.docx

CSS220_Module4_Homework1.docx

CSS 220 Module 4 Homework

Think about how many messages are sent electronically today. What are most common? Email, text messages, in-app messaging? And what kind of data gets sent? Is it secure? For it to be secure during transmission, it needs to be encrypted. Do you know if your messages are encrypted? It is not hard to do. Let’s work through some classic encryption techniques.

Then when it arrives and the receiver wants to look at your message, they can perform a decryption. All forms of encryption rely on two basic forms of ciphers: substitution-based and transposition-based. Good encryption algorithms actually use multiple layers of both cipher forms. Let’s look at each form in more detail.

Substitution-based Ciphers

Have you ever seen the cryptoquote puzzles in the newspaper? You can try to solve one here: https://api.razzlepuzzles.com/cryptogram.

Despite its daunting name, the substitution-based cipher is actually a fairly simple encryption technique. A substitution-based cipher replaces a character or group of characters with a different character or group of characters. Consider the following simple example. Each letter in the plaintext row maps onto the letter below it in the ciphertext row.

Plaintext: abcdefghijklmnopqrstuvwxyz

Ciphertext: POIUYTREWQLKJHGFDSAMNZVCXB

This ciphertext simply corresponds to the letters on a keyboard, scanning right to left, top to bottom. To send a message using this encoding scheme, each plaintext letter of the message is replaced with the ciphertext character directly below it. Thus, the message

what are you doing after class?

would encode to

VEPMP STXGN UGWHR PTMYS IKPAA

A space has been placed after every five ciphertext characters to help disguise obvious patterns.

1. Using the above plaintext and corresponding ciphertext, encode the message “i will encrypt everything”.

A famous substitution cipher is the Caesar Cipher, created and used by Julius Caesar. This cipher uses what is called a shift technique. Similar to above, you will make substitutions, but is a bit easier to code and decode. The transformation can be represented by aligning two alphabets; the cipher alphabet is the plain alphabet shifted left or right by some number of positions (the key).

For instance: Key = left shift 7 spaces

Plaintext: abcdefghijklmnopqrstuvwxyz

Ciphertext: TUVWXYZABCDEFGHIJKLMNOP

2. Create your own message and encode it using the Caesar Cipher method. Provide your key to decode the message.

Transposition-based Ciphers

A transposition-based cipher is different from a substitution-based cipher in that the order of the plaintext is not preserved. Rearranging the order of the plaintext characters makes common patterns unclear and the code much more difficult to break. Let us consider a simple example of a transposition cipher. Choose a keyword that contains no duplicate letters, such as COMPUTER. Over each letter in the keyword, write the number that corresponds to the order in which that letter appears in the alphabet when compared to the other letters in the keyword. For the keyword COMPUTER, C appears first in the alphabet, E is second, M is third, O is fourth, and so on.

14358726

COMPUTER

Take a plaintext message such as “this is the best class i have ever taken” and write it under the keyword in consecutive rows going from left to right.

14358726

COMPUTER

thisisth

ebestcla

ssihavee

vertaken

To encode the message, read down each column starting with the column numbered 1 and proceeding through to the column numbered 8. Reading column 1 gives us TESV, and column 2 gives us TLEE. Encoding all eight columns gives us the following message:

TESVTLEEIEIRHBSESSHTHAENSCVKITAA

Two interesting observations can be made about this example. First, the choice of the keyword is once again very important, and care must be taken to make sure the keyword does not fall into the wrong hands. Second, you could make the encryption even more difficult by performing an additional substitution-based cipher on the result of the transposition cipher. In fact, why stop there? You could create a very difficult code if you repeated various patterns of substitution- and transposition-based ciphers, one after another.

3. Using the keyword JUNIOR, encode the message “I need some caffeine to stay awake in class”.

4. One of the most common forms of communication today is email. It is used for everyday conversations as well as important business decisions. If email is so important, do you or anyone you know send encrypted email? Using the email program of your choice, tell how you can encrypt your emails. Is there an option in your email program to create an encrypted message? If not, is there a third-party vendor on the Internet that will encrypt your messages? Describe it. Sending a message over an https connection is not good enough.

How it Works

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  2. Fіll іn yоur paper’s іnfоrmatіоn and clіck “PRІCE CALCULATІОN” at the bоttоm tо calculate yоur оrder prіce.
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Nоte, оnce lоgged іntо yоur accоunt; yоu can clіck оn the “Pendіng” buttоn at the left sіdebar tо navіgate, make changes, make payments, add іnstructіоns оr uplоad fіles fоr the оrder created. e.g., оnce lоgged іn, clіck оn “Pendіng” and a “pay” оptіоn wіll appear оn the far rіght оf the оrder yоu created, clіck оn pay then clіck оn the “Checkоut” оptіоn at the next page that appears, and yоu wіll be able tо cоmplete the payment.

Meanwhіle, іn case yоu need tо uplоad an attachment accоmpanyіng yоur оrder, clіck оn the “Pendіng” buttоn at the left sіdebar menu оf yоur page, then clіck оn the “Vіew” buttоn agaіnst yоur Order ID and clіck “Fіles” and then the “add fіle” оptіоn tо uplоad the fіle.

Basіcally, іf lоst when navіgatіng thrоugh the sіte, оnce lоgged іn, just clіck оn the “Pendіng” buttоn then fоllоw the abоve guіdelіnes. оtherwіse, cоntact suppоrt thrоugh оur chat at the bоttоm rіght cоrner

NB

Payment Prоcess

By clіckіng ‘PRОCEED TО CHECKОUT’ yоu wіll be lоgged іn tо yоur accоunt autоmatіcally where yоu can vіew yоur оrder detaіls. At the bоttоm оf yоur оrder detaіls, yоu wіll see the ‘Checkоut” buttоn and a checkоut іmage that hіghlіght pоssіble mоdes оf payment. Clіck the checkоut buttоn, and іt wіll redіrect yоu tо a PayPal page frоm where yоu can chооse yоur payment оptіоn frоm the fоllоwіng;

  1. Pay wіth my PayPal accоunt‘– select thіs оptіоn іf yоu have a PayPal accоunt.
  2. Pay wіth a debіt оr credіt card’ or ‘Guest Checkout’ – select thіs оptіоn tо pay usіng yоur debіt оr credіt card іf yоu dоn’t have a PayPal accоunt.
  3. Dо nоt fоrget tо make payment sо that the оrder can be vіsіble tо оur experts/tutоrs/wrіters.

Regards,

Custоmer Suppоrt

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