Chapter 7 PKI and Cryptographic Applications

Question 1

disadvantage—the algorithm doubles the length of any message it encrypts.

Answer 1

El Gamal

Question 2

SHA-1 produces a ____-bit message digest.

and processes a message in ___-bit blocks.

Answer 2

160 , 512

Question 3

SHA-256 produces a ___-bit message digest using a ___-bit block size.

Answer 3

256, 512

Question 4

SHA-224 uses a truncated version of the SHA-256 hash to produce a __-bit message digest using a ___-bit block size.

Answer 4

224, 512

Question 5

SHA-512 produces a ___-bit message digest using a ____-bit block size.

Answer 5

512, 1024

Question 6

SHA-384 uses a truncated version of the SHA-512 hash to produce a ___-bit digest
using a ____-bit block size.

Answer 6

384 , 1024

Question 7

MD2 pads the message so that its length is a multiple of __ bytes

Answer 7

16

Question 8

MD2 generates a ___-bit message.

Answer 8

128

Question 9

______ computes a 16-byte checksum and appends it to the end of the message.

Answer 9

MD2

Question 10

__ pads the message to ensure that the message length is 64 bits smaller than a multiple of 512 bits.

Answer 10

MD4 , MD5

Question 11

MD4 algorithm then processes ___-bit blocks of the message in three rounds of computation. The final output is a ____-bit message digest.

Answer 11

512, 128

Question 12

Difference between MD4 and MD5 is that MD4 uses 3 rounds MD5 uses rounds.

Answer 12

true

Question 13

Digital Signature Standard consists of which encryption algorithms ?

Answer 13

The Digital Signature Algorithm (DSA)

The Rivest, Shamir, Adleman (RSA)

The Elliptic Curve DSA (ECDSA)

Question 14

Steganographic algorithms work by making alterations to the _____ significant bits of the many bits that make up image files.

Answer 14

least

Question 15

protects entire communications circuits by creating a secure tunnel between two points using either a hardware solution or a software solution that encrypts all traffic entering one end of the tunnel and decrypts all traffic entering the other end of the tunnel.

End-to-end encryption
Link encryption

Answer 15

Link encryption

Question 16

does not encrypt the header, trailer, address, and routing data, so it moves faster from point to point but is more susceptible to sniffers and eavesdroppers.

End-to-end encryption
Link encryption

Answer 16

End-to-end encryption

Question 17

IPsec relies on security associations, and

there are two main components:

Answer 17

The Authentication Header (AH

The Encapsulating Security Payload (ESP)

Question 18

IPsec provides for two discrete modes of operation _____ and _________

Answer 18

transport mode and tunnel mode

Question 19

_____ mode , the entire packet, including the header, is encrypted.

Answer 19

tunnel mode

Question 20

only the packet payload is encrypted.

Answer 20

transport mode

Question 21

When encryption happens at the higher OSI layers, it is usually ______ encryption,

Answer 21

end-to-end

Question 22

if encryption is done at the lower layers of the OSI model, it is usually ____ encryption

Answer 22

link

Question 23

The attacker responds to the originator’s initialization requests and sets up a
secure session with the originator. The attacker then establishes a second secure session with the
intended recipient using a different key and posing as the originator.

Analytic Attack

Implementation Attack

Statistical Attack

Brute Force

Frequency Analysis and the Ciphertext Only Attack

Known Plaintext

Chosen Ciphertext

Chosen Plaintext

Meet in the Middle

Man in the Middle

Replay

Answer 23

Man in the Middle

Question 24

the attacker uses a known plaintext message. The
plain text is then encrypted using every possible key (k1), and the equivalent ciphertext is decrypted using all possible keys (k2). When a match is found, the corresponding pair (k1,
k2) represents both portions of the double encryption

Analytic Attack

Implementation Attack

Statistical Attack

Brute Force

Frequency Analysis and the Ciphertext Only Attack

Known Plaintext

Chosen Ciphertext

Chosen Plaintext

Meet in the Middle

Man in the Middle

Replay

Answer 24

Meet in the Middle

Question 25

the attacker has the ability to encrypt plaintext messages of their choosing and can then analyze the ciphertext output of the encryption algorithm. Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle Replay

Answer 25

Chosen Plaintext

Question 26

the attacker has the ability to decrypt chosen portions of the ciphertext message and use the decrypted portion of the message to discover the key. Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle Replay

Answer 26

Chosen Ciphertext

Question 27

the attacker has a copy of the encrypted message along with the plaintext message used to generate the ciphertext Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle Replay

Answer 27

Known Plaintext

Question 28

counting the number of times each letter appears in the ciphertext. Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle

Answer 28

Frequency Analysis and the Ciphertext Only Attack

Question 29

attempts every possible valid combination for a key or password. They involve using massive amounts of processing power to methodically guess the key used to secure cryptographic communications Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle

Answer 29

Brute Force

Question 30

attempt to find a vulnerability in the hardware or operating system hosting the cryptography application Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle

Answer 30

Statistical Attack

Question 31

focuses on exploiting the software code, not just errors and flaws but the methodology employed to program the encryption system.Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle

Answer 31

Implementation Attack

Question 32

algebraic manipulation that attempts to reduce the complexity of the algorithm and focuses on the logic of the algorithm itself Analytic Attack Implementation Attack Statistical Attack Brute Force Frequency Analysis and the Ciphertext Only Attack Known Plaintext Chosen Ciphertext Chosen Plaintext Meet in the Middle Man in the Middle Replay

Answer 32

Analytic Attack

Question 33

Keys used within public key systems must be ____ than those used in private key systems to produce cryptosystems of equivalent strengths

Answer 33

longer

Question 34

Which algorithm has these steps: 1. Choose two large prime numbers (approximately 200 digits each), labeled p and q. 2. Compute the product of those two numbers: n = p * q.

Answer 34

RSA public key algorithm

Question 35

Name asymmetrical algorithms ( 3 )

Answer 35

Elliptic Curve El Gamal RSA

Question 36

According to RSA Security, there are five basic requirements for a cryptographic hash function:

Answer 36

The input can be of any length. The output has a fixed length. The hash function is relatively easy to compute for any input. The hash function is one-way (meaning that it is extremely hard to determine the input when provided with the output). One-way functions and their usefulness in cryptography are described in Chapter 6. The hash function is collision free (meaning that it is extremely hard to find two messages that produce the same hash value).

Question 37

Which algorithm pads the message with | additional data until the length reaches the next highest multiple of 512.

Answer 37

SHA

Question 38

If Alice wants to digitally sign a message she’s sending to Bob, Alice then encrypts only the message digest using ______

Answer 38

her private key

Question 39

If Alice wants to digitally sign a message she’s sending to Bob, Bob decrypts the digital signature using ____ _______ .

Answer 39

Alice’s public key

Question 40

S/MIME uses the ____- encryption algorithm

Answer 40

RSA

Question 41

S/MIME relies on the use of __ for exchanging cryptographic keys.

Answer 41

X.509 certs