Review Questions
1. How many keys exist in a public/private key pair?
A. 1
B. 2
C. 3
D. 4
2. How many keys are needed for symmetric key encryption?
A. 1
B. 2
C. 3
D. 4
3. Which of the following key lengths would be considered uncrackable? (Choose all that
apply.)
A. 512
B. 256
C. 128
D. 64
4. What algorithm outputs a 128-bit message digest regardless of the length of the input?
A. SHA
B. MD5
C. RC4
D. RC6
5. What algorithm outputs a 160-bit key with variable-length input?
A. SHA
B. MD5
C. RC4
D. RC6
6. Which algorithm is used in the digital signature process?
A. RC4
B. RC5
C. Blowfish
D. MD5
7. What is cryptography?
A. The study of computer science
B. The study of mathematics
C. The study of encryption
D. The creation of encryption algorithms
8. What is the process of changing the order of some characters in an encryption key?
A. Transposition
B. Subtraction
C. Substitution
D. Transrelation
9. Data encrypted with the server’s public key can be decrypted with which key?
A. The server’s public key
B. The server’s private key
C. The client’s public key
D. The client’s private key
10. Which type of encryption is the fastest to use for large amounts of data?
A. Symmetric
B. Public
C. Private
D. Asymmetric
11. What is the goal of a known–plain text attack?
A. To read the encrypted data
B. To gain access to the public key
C. To discover the encryption key
D. To validate the sender of the data
12. Which cryptographic attack attempts to crack the code by looking for patterns and using
statistical analysis?
A. Cipher text–only attack
B. Chosen–plain text attack
C. Chosen–cipher text attack
D. Brute-force attack
13. Which two factors are of concern when using brute-force attacks against encryption?
A. Time
B. Money
C. Knowledge of the sender
D. The ability to capture data
14. Which program is useful in ensuring the integrity of a file that has been downloaded from
the Internet?
A. Tripwire
B. Norton Internet Security
C. Snort
D. WinMD5
15. What are some of the common fields in an x.509 certificate? (Choose all that apply.)
A. Secret Key
B. Expiration Date
C. Issuer
D. Public Key
16. What is the standard format for digital certificates?
A. x.500
B. x.509
C. x.25
D. XOR
17. What would the cipher text result be of a value of 1 in plain text and 0 in the secret key
after an XOR process?
A. 1
B. 0
18. What are two components of a PKI?
A. User passwords
B. Digital certificates
C. Encrypted data
D. CA
19. What element of the CIA triad ensures that the data sent is the same data received?
A. Confidentiality
B. Integrity
C. Authentication
20. What is the purpose of a hash?
A. To ensure confidentiality when using a public network such as the Internet
B. To ensure integrity of a transferred file
C. To ensure only authorized users are accessing a file
D. To ensure the data is available to authorized users
Answers to Review Questions
1. B. Two keys, a public key and a private key, exist in a key pair.
2. A. The same key is used to encrypt and decrypt the data with symmetric key encryption.
3. A, B. A key length of 256 bits or more is considered uncrackable.
4. B. MD5 outputs a 128-bit digest with variable-length input.
5. A. SHA outputs a 160-bit key with variable-length input.
6. D. MD5 is used in the digital signature process.
7. C. Cryptography is the study of encryption.
8. A. Transposition is the process of changing the order of some characters in an encryption
process.
9. B. Data can be decrypted with the other key in the pair—in this case, the server’s private key.
10. A. Symmetric key encryption is fast and best to use when you have large amounts of data.
11. C. The goal of a known–plain text attack is to discover the encryption key.
12. A. A cipher text–only attack attempts to crack the encryption using cryptoanalysis.
13. A, B. Time and money are the two biggest concerns when attempting to break encryption
using a brute-force method.
14. D. WinMD5 can be used to verify the integrity of a file downloaded from the Internet.
15. C, D. An x.509 certificate includes a field for Issuer and Public Key.
16. B. x.509 is the standard for digital certificates.
17. A. Different values such as 1 and 0 in an XOR process result in a value of 1.
18. B, D. CA (certificate authorities) and digital certificates are two components
of a PKI.
19. B. Integrity ensures the data is not modified in transit.
20. B. A hash is a one-way encryption used to validate the integrity of a file.