01 - Flash Cards

Question 1

Cryptography

Answer 1

• Cryptography is a security technology used to provide security, integrity and authentication to information that is either stored, in transit or in use.

Question 2

Caesar Cipher

Answer 2

• It is the earliest known cryptographic method used by Julius Caesar. In this cryptographic system, the coded message is formed by shifting every letter of the alphabet by three to the right.

Question 3

Goals of Cryptography

Answer 3

• Confidentiality
• Integrity
• Authentication
• Nonrepudiation

Question 4

Confidentiality

Answer 4

• Provides data privacy and security when data is being stored, in transit or used.

Question 5

Types of Cryptosystems

Answer 5

• Symmetric cryptosystem
• Asymmetric cryptosystem

Question 6

Symmetric cryptosystem

Answer 6

• All cryptosystem users have shared secret key available to them.

Question 7

Asymmetric cryptosystem

Answer 7

• Every user has an individual key which is a combination of public and private key.

Question 8

Three Types of Data in Cryptographic System

Answer 8

• Data at rest
• Data in motion
• Data in use

Question 9

Data at rest

Answer 9

• Data stored at a permanent location. For example hard drives, could etc

Question 10

Data in motion

Answer 10

• Data being transmitted between two systems, across a network.
• Also known as data on wire.

Question 11

Data in use

Answer 11

• Data located in the active memory of a computer.

Question 12

Integrity

Answer 12

• Provides assurance that data is not altered without authorization.

Question 13

Authentication

Answer 13

• An important feature of cryptosystems as it ensures the identity of a system user.

Question 14

Nonrepudiation

Answer 14

• Provides assurance to the recipient that the message was provided by the original sender and not someone masquerading as the sender.

Question 15

Plaintext Message

Answer 15

• Message before it is put into an encrypted form.
• It is labelled by letter P.

Question 16

Ciphertext Message

Answer 16

• Plaintext message encrypted by using a cryptographic algorithm. It is labelled by letter C.

Question 17

Key space

Answer 17

• Set of values that are allowed/valid to be used as a key for a particular algorithm. It is defined by a bit size.

Question 18

The Kerckhoff Principle

Answer 18

• Cryptographic system assumed to be secure even when everything about it, except the key, is known to the public.

Question 19

Cryptovariable

Answer 19

• Another name for cryptographic key.

Question 20

Cryptography

Answer 20

• Creation and implementation of codes and ciphers.

Question 21

Cryptanalysis

Answer 21

• Methods used for decoding/deciphering.

Question 22

Cryptology

Answer 22

• Combination of cryptography and cryptanalysis.

Question 23

Cryptosystem

Answer 23

• Installation of code/cipher into a software/hardware system.

Question 24

Boolean Mathematics

Answer 24

• Set of rules used to work with digital circuits (bytes and bits). It is a binary system based on two values - 1 and 0, true and false, respectively.

Question 25

AND Operation

Answer 25

* Operation that examines whether out of two values both values are true.

Question 26

OR Operation

Answer 26

* Operation that examines whether at least one of the values is true.

Question 27

NOT Operation

Answer 27

* Operation that reverse the value of the variable. * For example, 1 is changed to 0.

Question 28

Exclusive OR (XOR)

Answer 28

* Returns a true value when only one of the input variables is true. * In case that both variables are false or both variables are true, XOR output will be false.

Question 29

Modulo Function

Answer 29

* Finds a reminder of division of one number by another.

Question 30

One- Way Functions

Answer 30

* Operation that produces output values for all the possible combinations of a particular set of input variables. * However, it makes it impossible to retrieve the input variables.

Question 31

Nonce

Answer 31

* It is an arbitrary number that serves as a proxy variable in a mathematical function.

Question 32

Zero- Knowledge Proof

Answer 32

* Method by which one party can prove knowledge of a certain fact to another party without revealing the actual fact.

Question 33

Split Knowledge

Answer 33

* Information to perform a certain operation is split among users in such way that no single user has sufficient knowledge to compromise the security.

Question 34

Work Function

Answer 34

* A way to measure the strength of a particular cryptosystem. * The protection provided by a cryptosystem is directly correlated to its work factor/function.

Question 35

Code vs Cipher

Answer 35

* Code refers to symbol that may be used to substitute a word/phrase and does not necessarily provide confidentiality, while cipher is always meant to conceal data/information and provide confidentiality.

Question 36

Transposition Ciphers

Answer 36

* Algorithms used to transform plaintext into ciphertext.

Question 37

Substitution Ciphers

Answer 37

* Encryption method that substitutes every character in a plaintext with a different character.

Question 38

One-Time Pad

Answer 38

* Encryption method that uses different substitution alphabet for each character in a plaintext. It uses a key that is at least long as the message.

Question 39

Running Key Ciphers (Book Ciphers)

Answer 39

* Encryption key used is at least as long as a message and it is taken from a common book.

Question 40

Block Ciphers

Answer 40

* It is an encryption algorithm operating on a fixed number of bits, called a block.

Question 41

Stream Ciphers

Answer 41

* It is a key cipher that operates on one bit of a message or on one character at the time.

Question 42

Confusion

Answer 42

* An extremely complicated relationship between the plaintext and key that makes it impossible for the attacker to determine the key by changing the plaintext and analysing the its ciphertext.

Question 43

Diffusion

Answer 43

* One change in plaintext leads to multiple changes in the ciphertext.

Question 44

Weaknesses of Symmetric Cryptography

Answer 44

* Key distribution * Does not implement nonrepudiation * Algorithm is not scalable * Keys are to be regenerated often

Question 45

Strengths of Asymmetric Cryptography

Answer 45

* Addition of new users requires generation of only one key pair * User are more easily removed from the system * Key regeneration is required only when a private key is compromised * Provides integrity, authentication, and nonrepudiation * Key distribution is simple * Pre-existing communication link does not need to exist

Question 46

Data Encryption Standard

Answer 46

* 64-bit block cipher that was proposed in 1977 by the US government as a standard cryptosystem to be used for all government communication. * No longer considered to be secure.

Question 47

DES - Five Modes of Operation

Answer 47

* Electronic Code Book mode * Cipher Block Chaining mode * Cipher Feedback mode * Output feedback mode * Counter mode

Question 48

Electronic Code Book Mode

Answer 48

* Mode of operation that for every processed 64-bit block produces an encrypted block using the secret key.

Question 49

Cipher Block Chaining Mode

Answer 49

* Mode of operation that XORs each block of unencrypted text with the ciphertext preceding and then it encrypts it using DES algorithm.

Question 50

Cipher Feedback Mode

Answer 50

* Mode of operation that works against data produced in real time.

Question 51

Output Feedback Mode

Answer 51

* Mode of operation that XORs plaintext with a seed value.

Question 52

Counter Mode

Answer 52

* Mode of operation similar to CFB and OFB; uses a simple counter increments for each operation.

Question 53

Triple DES

Answer 53

* Adapted version of DES that uses three different keys.

Question 54

International Data Encryption Algorithm (IDEA)

Answer 54

* Algorithm that begins the operation with a 128-bit key which is then broken up into 52 16-bit subkeys. These keys then act on input text using XOR and mode of operations to produce cryptographic version of the message.

Question 55

Blowfish

Answer 55

* Expands on the IDEA principle as it allows the use of variable lengths keys ranging from 32-bit to 448-bit.

Question 56

Skipjack

Answer 56

* Algorithm that operates on 64-bit blocks, uses and 80-bit key, and uses the same modes of operation as DES. * It also supports escrows of encryption keys.

Question 57

Advanced Encryption Standard

Answer 57

* Block cipher that has been chosen to replace DES. * It uses three keys of different strengths: 128 bit, 192 bit, and 256 bit.

Question 58

Key Management Practices

Answer 58

* Safeguards around secret key creation, distribution, storage, destruction, recovery, and escrow.

Question 59

Symmetric Key Exchange

Answer 59

* Offline distribution * Public key encryption * Diffie-Hellman key exchange algorithm

Question 60

Symmetric Key Storage and Destruction Principles

Answer 60

* Never store the encryption key in the same site where encrypted data is located * Provide two different individuals with half of the key

Question 61

Key Escrow Approaches

Answer 61

* Fair cryptosystems * Escrowed encryption standard

Question 62

Fair Cryptosystems

Answer 62

* Secret keys are divided into 2 or more pieces and given to a third party.

Question 63

Escrowed Encryption Standard

Answer 63

* Basis behind Skipjack; it provides governments with the ability to decipher encrypted data.