Problem set 4: the Caesar Cipher



Yüklə 111,01 Kb.
Pdf görüntüsü
səhifə1/10
tarix17.02.2022
ölçüsü111,01 Kb.
#83821
  1   2   3   4   5   6   7   8   9   10
MIT6 00SCS11 ps4



Problem Set #4 

Handed out: Lecture 7 



Pseudocode: 11:59pm, Lecture 8. No late days can be used for this part of the assignment.

 

Due: 11:59pm, Lecture 10. 



Pseudocode Solutions 

Check your pseudocode against ours before you finish your implementation! 



Introduction 

Encryption is the process of obscuring information to make it unreadable without special 

knowledge. For centuries, people have devised schemes to encrypt messages — some better than 

others — but the advent of the computer and the Internet revolutionized the field. These days

it’s hard not to encounter some sort of encryption, whether you are buying something online or 

logging into Athena. 

A cipher is an algorithm for performing encryption (and the reverse, decryption). The original 

information is called plaintext. After it is encrypted, it is called ciphertext. The ciphertext 

message contains all the information of the plaintext message, but it’s not in a format readable by 

a human or computer without the proper mechanism to decrypt it; it should resemble random 

gibberish to those not intended to read it. 

A cipher usually depends on a piece of auxiliary information, called a key. The key is 

incorporated into the encryption process; the same plaintext encrypted with two different keys 

should have two different ciphertexts. Without the key, it should be difficult to decrypt the 

resulting ciphertext into readable plaintext. 

This assignment will deal with a well-known (though not very secure) encryption method called 

the Caesar cipher. In this problem set you will need to devise your own algorithms and will 

practice using recursion to solve a non-trivial problem. 



Caesar Cipher 

In this problem set, we will examine the Caesar cipher. The basic idea in this cipher is that you 

pick an integer for a key, and shift every letter of your message by the key. For example, if your 

message was “hello” and your key was 2, “h” becomes “j”, “e” becomes “g”, and so on. If you’re 

interested in learning more about the Caesar cipher, check out the 

Wikipedia article

In this problem set, we will use a variant of the standard Caesar cipher where the space character 



is included in the shifts: space is treated as the letter after “z”, so with a key of 2, “y” would 

become ” “, “z” would become “a”, and ” ” would become “b”. 





Yüklə 111,01 Kb.

Dostları ilə paylaş:
  1   2   3   4   5   6   7   8   9   10




Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©www.genderi.org 2024
rəhbərliyinə müraciət

    Ana səhifə