Chapter 5 - Cryptography

Front 1

What is cryptography?

Back 1

Cryptography is the science of hiding information in plain sight, in order to conceal it from unauthorized parties.

Front 2

What cipher did Ceasar use for battlefield communications?

Back 2

Substitution cipher.

Front 3

What was the first cipher used and by whom?

Back 3

Substitution cipher first used by Ceasar for battlefield communications.

Front 4

What is plaintext?

Back 4

An original message.

Front 5

What is ciphertext?

Back 5

An encrypted message.

Front 6

What is encryption?

Back 6

The process of transforming plaintext into ciphertext (also encipher).

Front 7

What is decryption?

Back 7

The process of transforming ciphertext into plaintext (also decipher).

Front 8

What is an encryption key?

Back 8

The text value required to encrypt and decrypt data.

Front 9

What are the 6 methods of encryption?

Back 9

1. Substitution
2. Transportation
3. Monoalphabetic
4. Polyalphabetic
5. Running-key
6. One time pads

Front 10

What are the 2 types of encryption?

Back 10

1. Block cipher
2. Stream cipher

Front 11

What are the 3 types of encryption keys?

Back 11

1. Symmetric key
2. Asymmetric key
3. One-time pad

Front 12

What is a symmetric key?

Back 12

A common secret that all parties who participate must know.

Front 13

What is an asymmetric key?

Back 13

• Public / private key
• Openly distribute public key to all parties.

Front 14

What is a one-time pad?

Back 14

Used once, is as large as the message to be encrypted.

Front 15

What was Ceasar's version of the substitution cipher?

Back 15

Ceasar rotated three to the right.

A > D, B > E, C > F, etc

Front 16

What is the substitution cipher?

Back 16

Plaintext characters are substituted to form ciphertext.

• A table or formula is used.

Front 17

What is the transposition cipher?

Back 17

• Plaintext messages are transposed into ciphertext.
• Write into column going down, read from columns to the right.

Front 18

What is the vulnerability of the transposition cipher?

Back 18

Subject to frequency analysis attack.

Front 19

What is a monoalphabetic cipher?

Back 19

One alphabetic character is substituted for another.

Front 20

What is the vulnerability of the monoalphabetic cipher?

Back 20

Subject to frequency analysis attack.

Front 21

What is a polyalphabetic cipher?

Back 21

Two or more substitution alphabets.

Front 22

What is the advantage of a polyalphabetic cipher?

Back 22

Not subject to frequency attack.

Front 23

What is a running-key cipher?

Back 23

• Plaintext letters converted to numeric (A=0, B=1, etc)
• Plaintext values "added" to key values giving ciphertext.
• Modulo arithmetic is used to keep results in range 0-26.

Front 24

What is Modulo arithmetic?

Back 24

Add 26 if result <0, subtract 26 if result >26.

Front 25

What is a one-time pad?

Back 25

• Works like running key cipher, except that key is length of plaintext, and is used only once.
• Highly resistant to cryptanalysis.

Front 26

What is a block cipher?

Back 26

Encrypt and decrypt a block of data at a time (typically 128 bits).

Front 27

What is the typical length of a block cipher?

Back 27

128 bits.

Front 28

What are the typical uses for a block cipher? (4)

Back 28

• Files
• E-mail messages
• Text communications
• Web

Front 29

What are the well known encryption algorithms for block ciphers? (7)

Back 29

1. DES
2. 3DES
3. AES
4. CAST
5. Twofish
6. Blowfish
7. Serpent

Front 30

For block cipher, what is Electronic Code Book?

Back 30

• Simplest block cipher mode
• Each block encrypted separately.

Front 31

For block cipher, what is Cipher-block Chaining (CBC)?

Back 31

• Ciphertext output from each encrypted plaintext block in encryption used for next block.
• First block encrypted with IV.

Front 32

What does IV stand for?

Back 32

Initialization vector.

Front 33

For block cipher, what is Cipher Feedback (CFB)?

Back 33

• Plaintext for block N is XOR'd with the ciphertext from block N-1.
• In the first block, the plaintext XOR'd with the encrypted IV.

Front 34

What does CBC stand for?

Back 34

Cipher-block Chaining (CBC)

Front 35

What does CFB stand for?

Back 35

Cipher Feedback

Front 36

What does OFB stand for?

Back 36

Output Feedback.

Front 37

For block cipher, what is Output Feedback?

Back 37

Plaintext is XOR'd with the encrypted material in the previous block to produce ciphertext.

Front 38

For block cipher, what is Counter?

Back 38

Uses a "nonce" (a random number that is used once) that is concatenated with a counter or other simple function, which is encrypted by the block cipher, and the output XOR'd with the plaintext block to produce the ciphertext block.

Front 39

What does CTR stand for?

Back 39

Counter.

Front 40

What are stream ciphers used for?

Back 40

Used to encrypt a continuous stream of data, such as an audio or video transmission.

Front 41

What is a stream cipher?

Back 41

A stream cipher is a substitution cipher that typically uses an exclusive -or (XOR) operation that can be performed very quickly by a computer.

Front 42

Plaintext 1 1 0 1 0

Key 0 1 1 0 0

Back 42

Ciphertext 1 0 1 1 0

Front 43

What is a symmetric key?

Back 43

Same key used at both ends of a communications channel or session

A symmetric key is also known as a shared secret

Front 44

List 7 encryption algorithms that use symmetric keys.

Back 44

1. DES
2. 3DES
3. AES
4. Twofish
5. Blowfish
6. IDEA
7. RC5

Front 45

What are asymmetric keys?

Back 45

• Overcomes the problem of communicating a shared secret to another party

• Key distribution scales better that symmetric cryptography.
• All parties can share each others' public keys.

Front 46

What encryption algorithms use asymmetric keys?

Back 46

1. RSA
2. EI Gamal
3. Elliptic Curve

Front 47

List 2 hardening techniques.

Back 47

1. Separation of duties

2. Split custody.

Front 48

List 8 cryptanalysis attacks.

Back 48

1. Frequency analysis
2. Brithday attacks
3. Ciphertext only attack
4. Chosen plaintext attack
5. Chosen ciphertext attack
6. Known plaintext attack
7. Man in the middle attack
8. Replay attack

Front 49

What are the uses for cryptography? (5)

Back 49

1. File encryption
2. Encrypted volumes and disks
3. E-mail
4. Web browsing - protects session contents from eavesdropping
5. Protecting network communications

Front 50

What type of encryption does WinZip version 9 use?

Back 50

AES.

Front 51

What does EFS stand for?

Back 51

Encrypting File System.

Front 52

What are the two common ways email is encrypted?

Back 52

1. PGP / GPG
2. S/MIME

Front 53

What does S/MIME stand for?

Back 53

Secure / Multipurpose Internet Mail Extensions

Front 54

What does PEM stand for?

Back 54

Privacy Enhanced Mail

Front 55

What does SSL/TLS stand for?

Back 55

Secure Sockets Layer / Transport Layer Security

Front 56

What is IPsec?

Back 56

Encrypts all packets between established pairs of hosts.

Front 57

What is key escrow?

Back 57

Keys held by a trusted third party.

Front 58

What is a message digest?

Back 58

The result of a cryptographic operation on a file or message.

• Fixed-length result regardless of message size.
• Impossible to derive original message from digest.

Front 59

What algorithms are used to create a message digest? (3)

Back 59

1. MD-5
2. SHA-1
3. HMAC

Front 60

What algorithms are used to create digital signatures? (3)

Back 60

1. DSA
2. EI Gamal
3. Elliptic Curve DSA

Front 61

What is a digital signature?

Back 61

• Message digest that is cryptographically combined with signer's private key.
• Requires public key cryptography.
• Verifies message integrity.
• Verifies identity of signer.

Front 62

What is non-repudiation?

Back 62

Inability for a user to repudiate (deny) an action, because of the methods used to permit or authorize the action.

Front 63

What does PKI stand for?

Back 63

Public Key Infrastructure

Front 64

What are two PKI platforms?

Back 64

• LDAP
• Microsoft Active Directory

Front 65

What is steganography?

Back 65

Data hidden in image files, subtle changes that the eye won't see; can be encrypted as well.

Front 66

What is watermarking?

Back 66

Like a digital signature - a visible or invisible mark that claims ownership.

Front 67

What is cryptanalysis?

Back 67

An attack on a cryptosystem.

Front 68

What is a PKI?

Back 68

is a network-based service used to store digital certificates or public encryption keys of individuals in a community.