Chapter 7: PKI and Cryptographic Applications

Question 1

_______ key cryptosystems assign each user a pair of keys: a public key and a private key.

Answer 1

Public

Question 2

y² = x³ + ax + b

Answer 2

elliptic curve formula

Question 3

An approach to key exchange that allows two individuals to generate a shared secret key over an insecure communications channel

Answer 3

Diffie–Hellman algorithm

Question 4

produces a 256-bit message digest using a 512-bit block size

Answer 4

SHA-256

Question 5

uses a truncated version of the SHA-256 hash that drops 32 bits to produce a 224-bit message digest using a 512-bit block size.

Answer 5

SHA-224

Question 6

produces a 512-bit message digest using a 1,024-bit block size

Answer 6

SHA-512

Question 7

uses a truncated version of the SHA-512 hash that drops 128 bits to produce a 384-bit digest using a 1,024-bit block size.

Answer 7

SHA-384

Question 8

a partial digital signature—it guarantees the integrity of a message during transmission, but it does not provide for nonrepudiation.

Answer 8

hashed message authentication code (HMAC)

Question 9

These neutral organizations offer notarization services for digital certificates.

Answer 9

Certificate authorities (CAs)

Question 10

counting the number of times each letter appears in the ciphertext

Answer 10

frequency analysis

Question 11

the attacker has a copy of the encrypted message along with the plaintext message used to generate the ciphertext (the copy)

Answer 11

Known Plaintext

Question 12

the attacker obtains the ciphertexts corresponding to a set of plaintexts of their own choosing

Answer 12

Chosen Plaintext

Question 13

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

Answer 13

Chosen Ciphertext

Question 14

Attackers might use a _______ attack to defeat encryption algorithms that use two rounds of encryption.

Answer 14

meet-in-the-middle

Question 15

a malicious individual sits between two communicating parties and intercepts all communications (including the setup of the cryptographic session)

Answer 15

Man in the Middle

Question 16

also known as a collision attack or reverse hash matching seeks to find flaws in the one-to-one nature of hashing functions

Question 17

used against cryptographic algorithms that don’t incorporate temporal protections. In this attack, the malicious individual intercepts an encrypted message between two parties (often a request for authentication) and then later “replays” the captured message to open a new session.

Answer 17

replay attack