Module 3: Cryptography

Question 1

The word “cryptography” is derived from the Greek kryptos, meaning ____.

Answer 1

The word “cryptography” is derived from the Greek kryptos, meaning hidden.

Question 2

The origin of cryptography is usually dated from about ____ with the Egyptian practice of ____.

Answer 2

The origin of cryptography is usually dated from about 2000 B.C., with the Egyptian practice of hieroglyphics.

Question 3

The first known use of a modern cipher was by ____ (____ B.C. to ____ B.C.), who did not trust his messengers when communicating with his governors and officers.

Answer 3

The first known use of a modern cipher was by Julius Caesar (100 B.C. to 44 B.C.), who did not trust his messengers when communicating with his governors
and officers.

Question 4

In recent times, ____ has turned into a battleground of some of the world’s best mathematicians and computer scientists.

Answer 4

In recent times, cryptography has turned into a battleground of some of the world’s best mathematicians and computer scientists.

Question 5

The ability to securely store and transfer sensitive information has proved a critical factor in success in war and business.

Answer 5

cryptography

Question 6

This is used in many applications like banking transactions cards, computer passwords, and e-commerce transactions.

Answer 6

cryptography

Question 7

There are three (3) types of cryptographic techniques used in general:

Answer 7

• Symmetric-key cryptography
• Hash functions
• Public-key cryptography

Question 8

What are the 6 classical encryption techniques?

Answer 8

1. caesar cipher
2. atbash cipher
3. affine cipher
4. keyword cipher
5. playfair cipher
6. vigenere cipher

Question 9

A type of substitution cipher in which each letter in the plaintext is replaced by a letter of some fixed number of positions down the alphabet.

Answer 9

caesar cipher

Question 10

Solve the caesar ciphertext with a shift of 7:

Kvu’a qbknl h ivvr if paz jvcly

Answer 10

Don’t judge a book by its cover

Question 11

Solve the caesar ciphertext with a shift of 3:

khoor

Answer 11

hello

Question 12

This was originally used to encrypt the Hebrew alphabet.

Answer 12

atbash cipher

Question 13

It is one of the earliest known substitution ciphers to have been used, and is very simple.

Answer 13

atbash cipher

Question 14

It simply reverses the plaintext alphabet to create the ciphertext alphabet. That is, “A” will be encrypted as “Z”, “B” as “Y”, and so on.

Answer 14

atbash cipher

Question 15

Solve the atbash ciphertext:

FMREVIHRGB

Answer 15

UNIVERSITY

Question 16

Convert the plaincipher to atbash ciphertext:

POLYTECHNIC

Answer 16

KLOBGVXSMRX

Question 17

It is a type of monoalphabetic substitution cipher, where each letter in the alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter.

Answer 17

affine cipher

Question 18

Each letter is enciphered with the function (ax + b) mod 26.

Answer 18

affine cipher

Question 19

Each letter is deciphered using what formula in affine cipher?

Answer 19

inverse of a * (c-b) mod 26

Question 20

To use this cipher method, construct the ciphertext alphabet, pick a keyword and write it down, ignoring repeated letters. Follow it with the letters of the alphabet that have not yet been used.

Answer 20

keyword cipher

Question 21

It was the first practical digraph substitution cipher.

Answer 21

playfair cipher

Question 22

The playfair cipher was invented in ____ by ____ but was name after ____ who promoted the use of the cipher.

Answer 22

The playfair cipher was invented in 1854 by Charles Wheatstone but was name after Lord Playfair who promoted the use of the cipher.

Question 23

This cipher removes the letter “J”, creates a 5x5 table of the new cipher table starting with the keyword and followed by the remaining non-duplicated letters of the alphabet.

Answer 23

playfair cipher

Question 24

It is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword.

Answer 24

vigenere cipher

Question 25

This cipher uses a 26×26 table with A to Z as the row heading and column heading.

Answer 25

vigenere cipher

Question 26

This is the repeating keyword to satisfy the number of letters from the encrypted text in a vigenere cipher.

Answer 26

keystream