10.1 Intro to Cryptography

Question 1

Define cryptography

Answer 1

Cryptography is the art and science of keeping information secure through the use of mathematical concepts and techniques.

Question 2

Define:

Plaintext

Answer 2

Information in human-readable form.

Question 3

Define:

Ciphertext

Answer 3

Plaintext message that has been encrypted into an unreadable form.

Question 4

Define:

Encryption

Answer 4

Process of converting plaintext to ciphertext.

Question 5

Define:

Decryption

Answer 5

Process of converting ciphertext to plaintext.

Question 6

Define:

Cipher

Answer 6

Method of performing encryption or decryption.

Question 7

Define:

Key

Answer 7

Parameter specifying how plaintext is converted to ciphertext and vice versa.

Question 8

Define:

Caesar Cipher

Answer 8

Type of cipher that shifts the letters in the alphabet by a fixed number.

Question 9

Define:

Enigma cipher

Answer 9

Type of cipher used by Germany in World War II to encrypt messages.

Question 10

What is ASCII stand for and what is it?

Answer 10

ASCII stands for the American Standard Code for Information Interchange. It’s a code for representing English characters as numbers, assigned from 0 to 127

Question 11

What’s the goal of encoding?

Answer 11

The goal of encoding isn’t to keep a message secret, but to transform data to be used by another system.

Question 12

True or False

Encoding, unlike encryption, does not use a key.

Answer 12

True

Question 13

True or False

Encoding is often used to transform binary data into digital text data, where encryption commonly takes place.

Answer 13

False

Encoding is often used to transform digital text data into binary data, where encryption commonly takes place.

Question 14

Goals of Cryptography

What is the P.A.I.N model.

Answer 14

Privacy

Authentication

Integrity

Non-repudiation

Question 15

________ keeps data secure from unauthorized parties.

Answer 15

Privacy keeps data secure from unauthorized parties.

Question 16

________ is used to confirm the identities of the sender and receiver of data.

Answer 16

Authentication is used to confirm the identities of the sender and receiver of data.

Question 17

________ ensures a message isn’t altered between when it’s sent and when it’s received.

Answer 17

Integrity ensures a message isn’t altered between when it’s sent and when it’s received.

Question 18

________ prevents the original sender from denying they were the sender.

Answer 18

Non-repudiation prevents the original sender from denying they were the sender.

Question 19

_________ apply their algorithm one bit (character) at a time.

Answer 19

Stream ciphers apply their algorithm one bit (character) at a time.

Question 20

One prominent stream cipher is the ___________

Answer 20

One prominent stream cipher is the substitution cipher.

Question 21

True or False

Substitution ciphers substitute out old values for new values of input message.

Answer 21

True

Question 22

_________ apply their algorithm to chunks of characters.

Answer 22

Block ciphers apply their algorithm to chunks of characters.

Question 23

One prominent block cipher is the _____________

Answer 23

One prominent block cipher is the transposition cipher.

1. Break the message into blocks of three characters.
2. Replace the first, second, and third character of each block with the third , first, and second character.
3. Combine rearranged text.

Question 24

True or False

Ciphers use mathematical formulas known as algorithms to encrypt and decrypt data.

Answer 24

True

Question 25

The main cipher categories are _____ and ______ ciphers.

Answer 25

The main cipher categories are block and stream ciphers.

Question 26

A type of stream cipher is the _________ cipher , and a type of block cipher is the _________ cipher.

Answer 26

A type of stream cipher is the substitution cipher, and a type of block cipher is the transposition cipher.

Question 27

True or False

Substitution ciphers replace each character with a completely different character.

Answer 27

True

Question 28

Each algorithm has a possible range of numbers that can be used as a key, known as a _______.

Answer 28

Each algorithm has a possible range of numbers that can be used as a key, known as a key space.

Question 29

For modern cryptography, key space is defined by the number of binary bits used in the key, known as _______.

Answer 29

For modern cryptography, key space is defined by the number of binary bits used in the key, known as bit size.

Question 30

What is the formula for bit size?

Answer 30

Key space = 2 (to the power of bit size)

Question 31

True or False

Modern symmetric key algorithms use algorithms that are secure and fast.

Answer 31

True

Question 32

What are the widely known symmetric key algorithms?

Answer 32

• Data Encryption Standard (DES),
• Triple DES (3DES)
• Advanced Encryption Standard (AES)

Question 33

What does DES stand for?

Answer 33

Data Encryption Standard (DES) is a 56-bit key published by the United States government in 1977.