Ch. 7

Question 1

If Richard wants to send an encrypted message to Sue using a public key crypto system, which key does he use the encrypt the message?

A. Richard’s public key
B. Richard’s private key
C. Sue’s public key
D. Sue’s private key

Answer 1

C. Sue’s public key

Question 2

If a 2048-bit plaintext message were encrypted with the El Gamal public key crypto system, how long would the resulting cipher-text message be?

A. 1024 bits
B. 2048 bits
C. 4096 bits
D. 8192 bits

Answer 2

C. 4096 bits

Question 3

Acme widgets currently uses a 1024-bit RSA encryption standard company wide. The company plans to convert from RSA to an elliptic curve crypto-system. If he wants to maintain the same cryptographic strength, what ECC key length should he use?

A. 160 bits
B. 512 bits
C. 1024 bits
D. 2048 bits

Answer 3

B. 512 bits

Question 4

Richard received an encrypted message sent to him from Sue. Which key should he use to decrypt the message?

A. Richard’s public key
B. Richard’s private key
C. Sue’s public key
D. Sue’s private key

Answer 4

B. Richard’s private key

Question 5

5. Acme Widgets currently uses a 1,024-bit RSA encryption standard companywide. The company plans to convert from RSA to an elliptic curve cryptosystem. If it wants to maintain the same cryptographic strength, what ECC key length should it use?

A. 160 bits
B. 512 bits
C. 1,024 bits
D. 2,048 bits

Answer 5

Answer: A

The elliptic curve cryptosystem requires significantly shorter keys to achieve encryption that would be the same strength as encryption achieved with the RSA encryption algorithm. A 1,024-bit RSA key is cryptographically equivalent to a 160-bit elliptic curve cryptosystem key.

Question 6

6. John wants to produce a message digest of a 2,048-byte message he plans to send to Mary. If he uses the SHA-1 hashing algorithm, what size will the message digest for this particular message be?

A. 160 bits
B. 512 bits
C. 1,024 bits
D. 2,048 bits

Answer 6

Answer: A

The SHA-1 hashing algorithm always produces a 160-bit message digest, regardless of the size of the input message. In fact, this fixed-length output is a requirement of any secure hashing algorithm.

Question 7

Which factor does NOT affect the relative strength of a cryptosystem?
A. The key exchange value
B. The encryption algorithm
C. The secret key length
D. The secret key secrecy

Answer 7

A. The key exchange value

Question 8

What is an example of a brute force attack?
A. Sending multiple ICMP messages to a Web server
B. Searching through a company’s trash
C. Using a program to guess passwords from a SAM file
D. Gathering packets from a network connection

Answer 8

C. Using a program to guess passwords from a SAM file

Question 9

You have been specifically asked to implement a stream cipher. Which cryptographic algorithm could you use?
A. RC4
B. RC5
C. RC6
D. MD5

Answer 9

A. RC4

Question 10

What is an algorithm that is used to create a message digest for a file to ensure integrity?
A. Plaintext
B. Hash
C. Ciphertext
D. Public Key

Answer 10

B. Hash