6. Cryptography and PKI – Security+® Practice Tests

6. Cryptography and PKI

Domain 6 Questions

  1. Adam created a message and then computed a message digest based upon that message. He then altered a single character at the end of the message and then recomputed the message digest. Which one of the following statements about the second message digest is correct?

    A. The second message digest should be one character different from the first digest.

    B. The second message digest will be completely different from the first digest.

    C. There may be minor differences in the second message digest,e but they will be toward the end of the digest.

    D. The two digests will essentially be the same, with minor differences.

  2. Which one of the following encryption algorithms does not rely upon the difficulty of factoring large prime numbers to achieve its secrecy?

    A. RSA

    B. PGP

    C. ECC

    D. Diffie-Hellman

  3. Helen is concerned about an attack that may retrieve credit card numbers from memory in a point-of-sale terminal. What term best describes this scenario?

    A. Data-in-transit

    B. Data-at-rest

    C. Data-in-use

    D. Data-on-disk

    Questions 4-7 refer to the following scenario:

    Renee and Mike are communicating using an asymmetric encryption algorithm. They each have the appropriate keys to participate in the communication.

    Renee would like to send a message to Mike and make use of encryption for several purposes.

  4. Renee would like confidentiality protection on the message that she sends Mike, and would like to achieve this by encrypting the message. What key should she use to encrypt the message?

    A. Mike's public key

    B. Mike's private key

    C. Renee's public key

    D. Renee's private key

  5. When Mike receives the message, what key should he use to decrypt it?

    A. Mike's public key

    B. Mike's private key

    C. Renee's public key

    D. Renee's private key

  6. Renee would also like to achieve non-repudiation by applying a digital signature to the message. What key should she use to encrypt the message digest?

    A. Mike's public key

    B. Mike's private key

    C. Renee's public key

    D. Renee's private key

  7. When Mike receives the message, he would like to verify the digital signature. What key should he use to decrypt the signature?

    A. Mike's public key

    B. Mike's private key

    C. Renee's public key

    D. Renee's private key

  8. Carol is designing a wireless network for use in a coffee shop. Her primary concern is ensuring that users have easy access to the network. Which one of the following wireless network types is most appropriate for her needs?

    A. WPA-PSK

    B. Open

    C. WPA-Enterprise

    D. WPA2-Enterprise

  9. Which one of the following statements about the Blowfish algorithm is incorrect?

    A. The algorithm is covered by a patent.

    B. The algorithm uses a 64-bit block size.

    C. The algorithm allows the use of any length key between 32 and 448 bits.

    D. The developer of the algorithm does not recommend it for use today.

  10. Norm would like to allow users to memorize passwords that may be used to protect strong encryption keys. What technique could he use to generate strong keys from those relatively short passwords?

    A. Key stretching

    B. Key escrow

    C. Key exchange

    D. Key revocation

  11. Which one of the following properties should NOT be found in a cryptographic hash function?

    A. Defined range

    B. One-way

    C. Collision

    D. Reproducible

  12. Darryl is concerned about the level of security provided by the encryption of Microsoft Office documents. What component of Windows could he upgrade to allow the use of stronger encryption with these documents?

    A. CRL

    B. CSP

    C. PKI

    D. SP

  13. When creating a digital certificate, what key does the certificate authority use to prevent the public disclosure of the certificate's public key?

    A. The certificate owner's private key

    B. The CA's private key

    C. The CA's public key

    D. No key

  14. Solve the exclusive or (XOR) operation shown here:

    Figure 6.1

    A. 0011

    B. 1100

    C. 0111

    D. 1000

  15. As you increase the length of a key by a single bit, how much more resilient does that key become against a brute force attack?

    A. Twice as strong

    B. One percent stronger

    C. 10 times stronger

    D. Four times stronger

  16. David encountered a cryptographic implementation using the RC4 stream cipher with a weak key and he would like to secure this implementation. What action should he take?

    A. Apply the algorithm three times

    B. Increase the key length

    C. Replace the cipher algorithm

    D. Apply the algorithm twice

  17. Will is creating a digital certificate for his web server. He will request the certificate from his internal corporate CA, which is an intermediate CA validated by the GeoTrust root CA. Who would create the CSR in this case?

    A. GeoTrust creates the CSR after receiving a request from Will

    B. Will creates the CSR on the GeoTrust website

    C. Will creates the CSR on the web server

    D. The internal CA creates the CSR after receiving a request from Will

  18. Which one of the following approaches to cryptography is least useful for data in transit over a network?

    A. FDE

    B. File encryption

    C. TLS

    D. AES

  19. Kaitlyn is selecting a wireless encryption algorithm for use in her organization. If she is able to choose from the following options, which would be the best choice?

    A. WPA

    B. WPA2

    C. WEP

    D. WPS

  20. Which one of the following block cipher modes of operation may NOT be used to turn a block cipher into a stream cipher?

    A. OFB

    B. GCM

    C. CTM

    D. ECB

  21. Ron is troubleshooting an application that is having trouble communicating with a RADIUS authentication server to validate user credentials. He believes that the issue may be a firewall problem. What port should he verify is accessible through the firewall from the application to the RADIUS server?

    A. 1812

    B. 1521

    C. 1433

    D. 3389

  22. Which one of the following statements about block and stream ciphers is correct?

    A. Most modern ciphers are block ciphers

    B. Stream ciphers commonly use Feistel networks

    C. Block ciphers are faster than equivalent stream ciphers

    D. Block ciphers encrypt 1 byte at a time

  23. Paul is sending a message to Kathy using asymmetric cryptography. In the final stage of the process, he uses Kathy's public key to encrypt the message. What goal(s) of cryptography are met by this encryption?

    A. Confidentiality, integrity, and non-repudiation

    B. Confidentiality only

    C. Non-repudiation only

    D. Confidentiality and integrity only

  24. When configuring cipher suites for a web server, which one of the following key exchange approaches would produce the strongest security?

    A. DHE Group 1

    B. DHE Group 2

    C. Export cipher suite

    D. ECDHE

  25. Harold is connecting to a wireless network that uses the 802.1x protocol. What term best describes the operating system component on his computer that interacts with the 802.1x service?

    A. The authentication server

    B. The client

    C. The supplicant

    D. The access server

  26. Which one of the following message-digest sizes is supported by the SHA-3 hash algorithm?

    A. 256 bits

    B. 224 bits

    C. SHA-3 supports any size digest

    D. 384 bits

  27. Alan is developing a new application that will rely upon cryptography. Which one of the following techniques is the best way for him to ensure that the cryptography is properly implemented?

    A. Write the cryptographic code directly in his application

    B. Hire a vendor to develop a custom cryptographic module

    C. Use a popular open source cryptographic module

    D. Test the software prior to use

  28. Greg is using a pseudorandom number generator (PNRG) to create cryptographic keying material. Which element of the algorithm must be varied with each use to prevent reproduction attacks?

    A. The hash

    B. The algorithm

    C. The key

    D. The seed

  29. What block size is used by the Advanced Encryption Standard when encrypting and decrypting data?

    A. 64 bits

    B. 128 bits

    C. 192 bits

    D. 256 bits

  30. When designing an encryption algorithm, which elements of the algorithm should be preserved as secrets?

    A. Both keys and encryption techniques should be kept secret

    B. Encryption techniques

    C. Decryption techniques

    D. Cryptographic keys

  31. Andy is implementing a new VPN server and would like to use the Diffie-Hellman algorithm. Which one of the following DH groups is most secure?

    A. Group 2

    B. Group 14

    C. Group 19

    D. Group 5

  32. Rob is sending a message to Gary and, as part of that communication, he computes the hash value of the message using the SHA-1 algorithm. Which of the following options best describes the set of people who are able to compute that hash value if they have the original message?

    A. Only Rob can compute the hash

    B. Anyone can compute the hash

    C. Only Rob or Gary can compute the hash

    D. Only someone with the encryption key can compute the hash

  33. Seth is encrypting a document to provide confidentiality using a symmetric encryption algorithm. He is sending the document to Helena. Which key should he use to perform this encryption?

    A. A shared secret key

    B. Seth's public key

    C. Seth's private key

    D. Helena's public key

  34. Which one of the following cryptographic algorithms was chosen as the winner of the contest to implement the Advanced Encryption Standard (AES)?

    A. Twofish

    B. Rijndael

    C. Blowfish

    D. Serpent

  35. When storing passwords in a password file, what term is used to describe a random value combined with a password to reduce the risk of rainbow table attacks?

    A. Cream

    B. IV

    C. Nonce

    D. Salt

  36. What is the encrypted version of the message shown here when the ROT13 algorithm is used?

    Figure 6.2

    A. SECRET

    B. FRPERG

    C. $TR#T%

    D. XJHWJY

  37. What encryption protocol does the WPA2 algorithm use to provide confidentiality for wireless communications?

    A. 3DES

    B. TKIP

    C. DES

    D. CCMP

  38. What is the most commonly used secure message-digest length with the RIPEMD algorithm?

    A. 128 bits

    B. 160 bits

    C. 256 bits

    D. 320 bits

  39. What protocol was designed as an efficient and secure replacement for the use of CRLs to determine whether a digital certificate has been revoked by the certificate authority?

    A. CSR

    B. OSCP

    C. CSP

    D. TACACS

  40. Don would like to ensure that traveling users are provided with encryption services for all of their network connections while on the road. Which one of the following cryptographic technologies would best meet this need?

    A. SSH

    B. An encrypted web proxy

    C. A web browser supporting HTTPS

    D. A VPN

  41. Carl connects to a wireless network that is using strong encryption and encounters the message shown here. Which type of network might he be connecting to?

    Figure 6.3

    A. WPA2-PSK

    B. WPA-Enterprise

    C. WEP2-PSK

    D. WEP-Enterprise

  42. Bill is designing a security solution that must be able to encrypt network traffic without introducing a delay into the transmission of that traffic. What term best describes Bill's requirement?

    A. Low resiliency

    B. High latency

    C. Low latency

    D. High resiliency

  43. Nick is using AES encryption to protect files stored on his network. What is the simplest step he can take to improve the strength of that encryption?

    A. Apply a second encryption algorithm on top of AES

    B. Change algorithms

    C. Increase the key length

    D. Use two rounds of AES encryption

  44. Zack is purchasing a digital certificate for his organization's web server from a trusted certificate authority. He would like to choose the certificate that provides the highest degree of trust to site visitors. Which certificate type should he choose?

    A. EV

    B. OV

    C. DV

    D. NV

  45. Vincent and Fred would like to communicate with each other using the 3DES encryption algorithm. What key must Vincent have in order to successfully communicate with Fred?

    A. Vincent's private key

    B. A shared secret key

    C. Fred's public key

    D. Fred's private key

  46. ROT 13 is an example of what type of cipher?

    A. Cryptographically strong

    B. Transposition

    C. Substitution

    D. Hashing

  47. Which one of the following is not a disadvantage of using a CRL to revoke digital certificates?

    A. Fails to open if the client can't retrieve the CRL

    B. Slow updating

    C. Does not work for EV certificates

    D. Requires the client to search the CRL

  48. Ben is conducting forensic analysis and discovers an image stored on a computer entitled "Drug Formula." When he opens the file, he sees the image shown here. If someone did embed a formula in the file, what technique did they likely use?

    Figure 6.4

    A. A stream cipher

    B. Hashing

    C. Obfuscation

    D. Steganography

  49. Which one of the following risks would be addressed by applying full disk encryption to a computer?

    A. Malware infection on the device

    B. The theft of the device

    C. Eavesdropping on the network segment used by the device

    D. An insider attack

  50. Which one of the following security principles does NOT describe a standard best practice in cybersecurity?

    A. Least privilege

    B. Security through obscurity

    C. Separation of duties

    D. Defense in depth

  51. Sam is designing a new certificate authority (CA). He creates an initial CA and uses that CA to authorize several subordinate CAs that issue certificates to end users. He then disconnects the initial CA from the network to protect it against attack. Which one of the following terms best describes the initial CA?

    A. Online CA

    B. Intermediate CA

    C. Offline CA

    D. Unauthorized CA

  52. The Tor network allows both participants in the communication to remain anonymous by filtering traffic through a number of relay nodes. What term describes the technology used by Tor to ensure anonymity?

    A. Perfect forward secrecy

    B. Security through obscurity

    C. Obfuscation

    D. Non-repudiation

  53. Brianne is accessing a website over a TLS connection. When her browser retrieves the digital certificate from the website, what key should she use to verify that the certificate may be trusted?

    A. The CA's public key

    B. The CA's private key

    C. The website's public key

    D. The website's private key

  54. Carla is examining her wireless access point and notices that it bears the logo shown here. What technology does this access point support?

    Figure 6.5

    A. WPS

    B. WPA2

    C. WPA

    D. WEP

  55. How many times must the DES encryption algorithm be applied to data in order to achieve a reasonable level of security?

    A. 1

    B. 2

    C. 3

    D. It is not possible to implement DES in a secure manner

  56. What does the PGP algorithm use to facilitate the trusted exchange of public keys between users?

    A. Certificate authorities

    B. Web of trust

    C. A central key management server

    D. BitTorrent

  57. What standard is used to define the format of a digital certificate?

    A. X.509

    B. 802.1x

    C. RFC 1918

    D. RFC 783

  58. What mathematical principle does the RSA algorithm rely upon for security?

    A. Cosine law

    B. Prime factorization

    C. Elliptic curve

    D. Ohm's law

  59. Brian is designing a communications system for the exchange of stock transactions. He wants to implement a system where a customer cannot later claim that someone else placed an order on their behalf. What goal of cryptography is he attempting to achieve?

    A. Integrity

    B. Authentication

    C. Confidentiality

    D. Non-repudiation

  60. Barry is configuring 802.1x authentication for his wireless network. In a typical wireless authentication scenario, what device would act as the 802.1x client?

    A. The backend authentication server

    B. Mobile devices connecting to the network

    C. The router

    D. A wireless access point

  61. Victor is evaluating the encryption algorithm options available for use in his organization. Of the options presented here, which would provide Victor with the strongest level of encryption?

    A. AES

    B. 2DES

    C. DES

    D. RC4

  62. Which mode of cipher operation is shown here?

    Figure 6.6

    A. OFB

    B. CFB

    C. ECB

    D. CBC

  63. Which one of the following keying options creates the most secure implementation of the 3DES encryption algorithm?

    A. K1=K2=K3

    B. K1, K2, and K3 are independent

    C. K1=K2; K2 is not equal to K3

    D. K2=K3; K1 is not equal to K3

  64. Which one of the following is not a secure technique for exchanging encryption keys?

    A. An emailed key

    B. The Diffie-Hellman algorithm

    C. Digital certificates

    D. In-person exchange

  65. Frank accesses a website over HTTPS using a standard web browser. After his browser retrieves the site's digital certificate and validates the signature, what piece of critical information does it extract from the certificate to continue the communication session?

    A. The web server's private key

    B. The web server's public key

    C. The CA's public key

    D. The CA's private key

  66. What encryption key length is used by the original Data Encryption Standard (DES)?

    A. 16 bits

    B. 56 bits

    C. 112 bits

    D. 128 bits

  67. What technology does the PEAP protocol combine with EAP to provide the secure communication of authentication credentials?

    A. IDEA

    B. SSL

    C. LEAP

    D. TLS

  68. Shannon is assisting a business unit with the implementation of an approach that may be used to verify the integrity and authenticity of a message. Which one of the following algorithms would best meet this need?

    A. SHA-3

    B. AES

    C. SHA-2

    D. HMAC

  69. Jerry is examining the cipher suites available for use on his organization's web server and finds the following supported options. Which one of these is it most important for him to remove?

    A. TLS_DHE_RSA_WITH_AES_128_GCM-SHA256

    B. TLS_RSA_WITH_RC4_128_SHA

    C. TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA

    D. TLS_RSA_WITH_3DES_EDE_CBC_SHA

  70. Riley would like to perform port-based authentication on her network and is seeking an authentication protocol specifically designed for this purpose. Which protocol would best meet her needs?

    A. RADIUS

    B. 802.1x

    C. Kerberos

    D. TACACS

  71. Bill is configuring a web server to use TLS cryptography. When the server is up and running, how many users will share each ephemeral session key?

    A. 1

    B. 2

    C. 4

    D. All users use the same session key

  72. What is the main reason for using an ephemeral symmetric session key within a TLS session rather than simply using asymmetric encryption keys for communication?

    A. Symmetric cryptography is more secure than asymmetric cryptography

    B. Symmetric cryptography is faster than asymmetric cryptography

    C. Asymmetric cryptography can only be used to exchange keys and not to transfer data

    D. Ephemeral keys can be reused

  73. Mike accesses the wireless network in a local coffee shop and sees the login screen shown here. What type of authentication is in use on this network?

    Figure 6.7

    A. WPA-PSK

    B. WPA-Enterprise

    C. Captive portal

    D. WPA2-Enterprise

  74. Examine the digital certificate shown here. What organization is asserting that the public key presented in this certificate actually belongs to Bank of America?

    Figure 6.8

    A. No such assertion is being made

    B. Bank of America Corporation

    C. eComm Network Infrastructure

    D. Entrust Certification Authority

  75. What cipher does EAP use to protect the confidentiality of authentication credentials passed using the protocol?

    A. 3DES

    B. AES

    C. No cipher

    D. RC4

  76. Which one of the following digital certificate types offers the lowest degree of assurance?

    A. EV

    B. OV

    C. DV

    D. XV

  77. Examine the digital certificate shown here. Which one of the following URLs would not be covered by this certificate?

    Figure 6.9

    A. https://www.mike.nd.edu/

    B. https://www.nd.edu/

    C. https://www.nd.edu/mike

    D. https://mike.nd.edu/

  78. Ray is configuring a highly secure web application that is being used by a limited number of users. He would like to apply a client-side control that informs the client browser exactly what certificate to expect from the server. Which one of the following controls meets his requirement?

    A. Certificate stapling

    B. Certificate pinning

    C. Certificate folding

    D. Certificate chaining

  79. Consider the digital certificate shown here. What format is the file used for this digital certificate?

    Figure 6.10

    A. .DER

    B. .PEM

    C. .P12

    D. .PFX

    Questions 80 and 81 refer to the following scenario:

    Ryan is evaluating potential encryption algorithms for use in his organization and would like to choose an approach that provides strong security.

  80. Ryan would like to ensure that the relationship between the encryption key and the ciphertext is quite complex so as to avoid reverse engineering. What property is he seeking to enforce?

    A. Diffusion

    B. Collusion

    C. Obfuscation

    D. Confusion

  81. Ryan would also like to prevent statistical analysis attacks by choosing an algorithm that prevents patterns in the plaintext from also appearing in the ciphertext. What property is he seeking to enforce?

    A. Diffusion

    B. Collusion

    C. Obfuscation

    D. Confusion

Domain 6 Answers and Explanations

  1. B. Message digests are one-way functions where it is not possible to reproduce the input by observing the output. To facilitate this, the digests produced by messages with even slight differences are completely different from each other. There is no way to assess the similarity of two messages by comparing their message digests.
  2. C. The Pretty Good Privacy (PGP), Rivest Shamir Adelman (RSA), and Diffie-Hellman algorithms all depend upon the difficulty of the prime factorization problem to achieve secrecy. The Elliptic Curve Cryptography (ECC) algorithm does not use prime numbers, and instead depends upon the mathematical properties of an elliptic curve.
  3. C. Data stored in memory is considered data in use, and is the most difficult scenario to protect against. Data at rest is data stored on a disk or other storage device, while data in transit is data being sent over a network.
  4. A. In an asymmetric encryption algorithm, the sender of a message achieves confidentiality by encrypting the message with the recipient's public key.
  5. B. In an asymmetric encryption algorithm, the recipient of a message decrypts the message by using the recipient's private key.
  6. D. In an asymmetric encryption algorithm, the sender of a message may achieve non-repudiation by digitally signing the message. To do this, the sender creates a message digest using a secure hash function and then signs that message digest their own private key.
  7. C. In an asymmetric encryption algorithm, the recipient of a digitally signed message decrypts the digital signature using the sender's public key. The recipient then computes the hash of the message using the same hash function used by the sender and compares the hash with the decrypted signature. If the hash and decrypted signature are identical, the message is authentic.
  8. B. In an open environment such as a coffee shop, the most effective approach is likely to use an unauthenticated, unencrypted network that users can connect to easily and simply. While this leaves communication unsecured, it minimizes the support needed and increases the likelihood that users will successfully connect. In this setup, users are responsible for providing their own encryption, if desired. This is an excellent example of conducting a risk/benefit analysis – the most secure option is not always the best choice!
  9. A. Bruce Schneier designed the Blowfish algorithm as an open source alternative to other patented encryption algorithms. The algorithm supports a 64-bit block size and variable length keys between 32 and 448 bits. Schneier does not recommend that people use Blowfish today, instead recommending the Twofish algorithm.
  10. A. Key stretching is a cryptographic technique used to turn a relatively weak key, such as a short password, into a stronger cryptographic key used to protect the confidentiality of information.
  11. C. Collisions occur when a hash function produces the same output for two different input values. This is a serious failure of the algorithm. Hash functions should have a defined range, as they often produce fixed-length output values. They should be one-way functions, meaning that it is not possible to obtain the plaintext from the hash. They should also be reproducible, meaning that anyone using the same hash function on the same input should receive the same hash value as output.
  12. B. Cryptographic Service Providers (CSPs) are components of Microsoft Windows that add support for specific encryption algorithms. Darryl can ensure that his systems are configured to use strong CSPs.
  13. D. The purpose of a digital certificate is to share a public key freely with the world. Therefore, the public key is not encrypted at all – it is freely given to anyone who receives the certificate.
  14. A. The exclusive or (XOR) operation is true when one, and only one, of the inputs is true. This means that one input must have a value of 1, while the other has a value of 0. Applying this operation to the problem shown here gives the answer of 0011.
  15. A. Adding a single bit to a cryptographic key doubles the number of possible keys, making the new key length twice as strong as the previous key length.
  16. C. The RC4 algorithm has inherent insecurities and should not be used under any circumstances. David should replace RC4 with another algorithm that meets modern security standards.
  17. C. In the process of creating a digital certificate, the requester creates a certificate signing request (CSR) on the device that will receive the certificate and then sends this CSR to the CA for use in creating the certificate.
  18. A. Full disk encryption is designed to protect data stored on a disk and would not affect data transmitted over a network. Transport Layer Security (TLS) is designed specifically to protect data being sent over network connections. File encryption may also be used to protect the contents of files being sent over a network. TLS and file encryption may both make use of the Advanced Encryption Standard (AES) to provide encryption and decryption functionality.
  19. B. The WPA2 algorithm is the current best practice standard for wireless encryption. The WPA algorithm is also considered secure, but is not the current best practice. The Wi-Fi Protected Setup (WPS) protocol is used to establish a wireless connection and is not an encryption standard. The Wired Equivalent Privacy (WEP) protocol is an outdated wireless encryption standard.
  20. D. The counter mode (CTM), Galois/counter mode (GCM), and output feedback (OFB) modes of operation may all be used to turn a block cipher into a stream cipher. The Electronic Code Book (ECB) mode retains the characteristics of a block cipher.
  21. A. RADIUS authentication may take place over TCP or UDP, and uses port 1812 in either case. TCP port 1521 is reserved for Oracle database communication, while TCP port 1433 is reserved for Microsoft SQL Server. TCP port 3389 is used by the Remote Desktop Protocol (RDP).
  22. A. It is true that block ciphers make up the vast majority of modern encryption algorithms. Stream ciphers are faster, not slower. than block ciphers. Block ciphers may make use of Feistel networks, while stream ciphers cannot. Block ciphers work on chunks of data, rather than a single byte at a time.
  23. D. When Paul encrypts the message with Kathy's public key, he provides confidentiality for the message because Kathy is the only one with the corresponding decryption key. When Kathy decrypts the message successfully, she also receives a guarantee of integrity because the message would not decrypt properly if it were altered. There is no guarantee of non-repudiation because Paul did not digitally sign the message.
  24. D. The Elliptic Curve Diffie-Hellman algorithm (ECDHE) is a strong, modern approach to key exchange. Export cipher suites are intentionally weak and should always be avoided. DHE groups 1 and 2 are also outdated and inappropriate for use in modern applications.
  25. C. In an 802.1x connection, the device that is actually attempting to connect to the network runs a software component known as the supplicant. This communicates with the network device performing the authentication, which is the client. That network device then communicates with the backend authentication server.
  26. C. The SHA-3 algorithm differs from earlier versions of SHA in that it supports an arbitrary message-digest length.
  27. C. Alan should rely upon a widely used and scrutinized cryptographic module because that code has likely been tested by thousands of users and many flaws have likely already been resolved. If Alan attempts to write or purchase custom code, it is highly likely that he will make a mistake and nobody will continue the development of the code on an ongoing basis. While Alan should test his software prior to use, this testing is unlikely to uncover subtle flaws in the cryptographic implementation.
  28. D. It is quite difficult to generate a truly random number, so modern computing applications use pseudorandom numbers. PNRGs depend upon a starting point, known as a seed value, to generate their sequence of random values. This seed value must be carefully selected and never reused to prevent an attacker from attempting to generate the same pseudorandom sequence.
  29. B. The Advanced Encryption Standard uses a 128-bit fixed block size. This should not be confused with the AES key length options of 128 bits, 256 bits, and 512 bits.
  30. D. Good security practice dictates that encryption and decryption algorithms should be open to public scrutiny to ensure their security. All of the secrecy in a cryptographic function should come from preserving the secrecy of the cryptographic keys.
  31. C. Diffie-Hellman group 19 uses a strong 256-bit elliptic curve key and is the best option of those presented here. Groups 2 and 5 use 1,024-bit and 1,536-bit modulus keys, respectively, and are not considered secure. Group 14 uses a 2,048-bit key and is minimally secure, but is weaker than group 19.
  32. B. Hash functions do not provide secrecy, and the results of a hash operation may be repeated by anyone with access to the hashed content. There are no encryption keys involved in computing a hash function. You may encrypt a hash value with a private key to create a digital signature, but there is no encryption or secrecy involved in creating the hash itself.
  33. A. In a symmetric encryption algorithm, all encryption and decryption is performed using a shared secret key. Public and private keys only exist in asymmetric encryption algorithms.
  34. B. The Rijndael algorithm won the AES competition and is the basis for the current AES. Twofish and Serpent were also competitors in the AES selection process. Twofish was a follow-on algorithm from Blowfish, which was not in the competition.
  35. D. A cryptographic salt is a value combined with a plaintext value prior to encryption or hashing to prevent the use of a rainbow table attack that precomputes encrypted or hashed values.
  36. B. The ROT13 algorithm simply shifts each character in a message by 13 values, so As become Ns, Bs become Os, Cs become Ps, and so on. Encrypting SECRET using this approach results in the word FRPERG.
  37. D. WPA uses the Temporal Key Integrity Protocol (TKIP) to rapidly cycle encryption keys and overcome the weaknesses of WEP. WPA2 uses the Counter Mode Cipher Block Chaining Message Authentication Code Protocol (CCMP) to provide enhanced security using AES.
  38. B. The RIPEMD algorithm supports all four of these message-digest lengths. The 160-bit digest is the most commonly used approach because it provides equivalent security to the 256- and 320-bit versions and stronger security than the insecure 128-bit version.
  39. B. The Online Certificate Status Protocol (OCSP) is a dynamic protocol designed to allow the real-time verification of digital certificates by end user devices. OCSP allows the immediate revocation of digital certificates without the time lag associated with the use of certificate revocation lists (CRLs).
  40. D. All of these techniques will provide some degree of cryptographic security. However, the best approach is to use a VPN that will tunnel all communications to the main office over a secure encrypted tunnel. A proxy using HTTPS will only support the specific applications that are proxied. The HTTPS web browser will only encrypt web communications. SSH will only provide encrypted terminal sessions between systems.
  41. A. This message is prompting the user to enter a pre-shared key (PSK) and, therefore, the network is in PSK mode. The question indicates that the network is secure, ruling out the use of WEP.
  42. C. Delays introduced into communications due to the overhead from encryption or other processing are known as latency. In a case where latency is unacceptable, architects should seek out low-latency technologies.
  43. C. The simplest way to improve the security of an already strong encryption algorithm is to increase the length of the key used by the algorithm. This is easier than switching algorithms, which would require new software.
  44. A. Extended Validation (EV) certificates are the most difficult to obtain, but provide the highest degree of trust for end users. Organization Validated (OV) certificates do verify the business name, but offer a lesser degree of trust than EV certificates. Domain Validated (DV) certificates only verify the domain name and provide the lowest degree of trust. NV certificates do not exist.
  45. B. Triple DES (3DES) is a symmetric encryption algorithm and, therefore, uses a shared secret key for communication. Public and private keys are only used by asymmetric encryption algorithms and are not relevant here.
  46. C. The ROT13 cipher exchanges each letter of a message for the letter that is 13 places ahead of it in the alphabet. This is an example of a substitution operation. Transposition ciphers rearrange the letters in a message, which is not occurring here. ROT13 is quite weak and would never be considered cryptographically strong. It also does not perform the hashing of messages into message digests.
  47. C. Certificate revocation lists (CRLs) have several disadvantages. They require the client to search the CRL for the serial number of a certificate to determine whether it was revoked. CRL implementations do fail to open so that a user will trust a certificate if the CRL is unavailable. They are also slow to update. CRLs do support EV certificates. They do not support OV or DV certificates.
  48. D. Individuals seeking to hide the existence of their communications may use a technique called steganography to hide data within another file. This is often done with image files by subtly altering the pixels of an image to encode the data in a manner that is imperceptible to the human eye.
  49. B. Full disk encryption is effective in data-at-rest situations where the data is not being actively accessed. For example, full disk encryption protects the contents of a lost or stolen device. Full disk encryption is not effective when a user has accessed the device legitimately, so it would not be effective against an insider attack or against malware running within a user account. It also does not protect data in transit, so it would not be effective against an eavesdropping attack.
  50. B. Security through obscurity is an outdated concept that says that the security of a control may depend upon the secrecy of the details of that control's inner function. Security professionals should not use controls that rely upon security through obscurity. The principles of least privilege, separation of duties, and defense in depth are all sound security practices.
  51. C. This certificate authority is a root CA, as it was the initial element in the chain of trust. The root CA was then used to create several intermediate CAs, but the root CA itself is not an intermediate CA. The root CA is disconnected from the network, so it is an offline CA, not an online CA. There is no indication that Sam was not authorized to create this CA, so it is not unauthorized.
  52. A. The Tor network uses perfect forward secrecy (PFS) to allow the relay nodes to forward communications to their end destination without knowing the identity of the sender or the receiver of the message.
  53. A. Digital certificates are signed by a certificate authority (CA). When a user or browser wishes to verify a digital certificate, it does so by validating the digital signature using the CA's public key.
  54. A. This logo indicates that the router supports Wi-Fi Protected Setup (WPS) for the establishment of a wireless connection.
  55. C. The DES algorithm may be made secure by applying it at least three times using at least two independent keys. This mode of operation is known as triple DES, or 3DES.
  56. B. The PGP package uses a concept known as the web of trust to provide assurances that keys are accurate. This decentralized model requires having keys vouched for by trusted individuals within the network and eschews a centralized approach.
  57. A. The digital certificate format is set out in the X.509 standard. RFC 1918 contains the standard for private IP addressing, while RFC 783 defines the TCP standard. IEEE 802.1x is a standard for wireless authentication.
  58. B. The RSA algorithm depends upon the difficulty of factoring the products of large prime numbers in order to achieve cryptographic security.
  59. D. Non-repudiation is the goal of ensuring that someone cannot later disclaim an action that they engaged in. It provides the ability for any third party to conclusively demonstrate the original source.
  60. D. In an 802.1x wireless network, the wireless access point or wireless controller typically serves as the 802.1x client, sending authentication requests to a backend authentication server.
  61. A. The Advanced Encryption Standard (AES) is a modern, secure algorithm. The Data Encryption Standard (DES) and Rivest Cipher 4 (RC4) are outdated and insecure. You may improve the security of DES by applying it to data three times (3DES), but for technical reasons, applying it twice (2DES) does not improve security.
  62. C. This image illustrates the Electronic Code Book (ECB) mode of cipher operation. You can determine this by noting that there is no link at all between the encryption operations.
  63. B. The most secure implementation of 3DES uses three independent keys. This approach creates a key with 168 (56x3) independent bits. When all three keys are the same, the key length is only 56 bits. When only two keys are independent, the key length is 112 bits.
  64. A. Email is an insecure data transfer mechanism and should not be used to transfer cryptographic keying material. Two parties wishing to communicate may use digital certificates to exchange public keys, establish a shared secret key using the Diffie-Hellman algorithm, or even exchange keys in person.
  65. B. The purpose of a digital certificate is to share a web server's public key. Frank's browser would extract this key from the certificate and use it to send the server an ephemeral session key to use for the remainder of the session.
  66. B. The Data Encryption Standard uses a 56-bit key. This short key length, along with some insecurities in the algorithm's design, makes it vulnerable to brute force key attacks.
  67. D. The Protected Extensible Authentication Protocol (PEAP) runs the standard EAP protocol within a TLS session to provide secure communications.
  68. D. The hash-based message authentication code (HMAC) algorithm supports both message integrity and authenticity. Hash algorithms without message authentication, such as MD5, SHA-2, and SHA-3, also support integrity, but not authenticity.
  69. B. Of these cipher suites, the only one using an insecure algorithm is TLS_RSA_WITH_RC4_128_SHA, which makes use of the outdated RC4 algorithm.
  70. B. The 802.1x protocol is an authentication protocol that is specifically designed to provide port-based authentication for wired networks as well as authentication for wireless networks.
  71. A. Web servers using TLS generate a new session key for each user that accesses the web server. Session keys are not reused, so as to preserve confidentiality between user sessions.
  72. B. The main reason that TLS uses asymmetric cryptography to establish a session and then switches over to symmetric cryptography using an ephemeral key is that symmetric cryptography is much faster than asymmetric cryptography. One approach is not necessarily more secure than the other, and both may be used to exchange data. Ephemeral keys are intended for use during a single session and should not be reused.
  73. C. The screen displayed here is a captive portal that is intercepting communications and requiring the user to complete the authentication process before gaining access to the network.
  74. D. This digital certificate is a valid digital certificate for www.bankofamerica.com and does include the organization name, Bank of America. Therefore, the certification authority, in this case Entrust, is making an assertion that the public key does indeed belong to Bank of America.
  75. C. The EAP protocol does not provide encryption capabilities and, therefore, must be run within a communications channel protected by other means.
  76. C. Domain Validated (DV) certificates only assure the recipient that the certificate authority has corroborated the fact that the certificate holder has possession of the domain name validated in the certificate. Extended Validation (EV) and Organizational Validation (OV) certificates go beyond this, requiring additional proof of identity. XV certificates do not exist.
  77. A. This certificate is a wildcard certificate with the wildcard character (*) put in place as a subdomain of nd.edu. Therefore, the certificate will work for any URL following the format https://*.nd.edu, followed by any other directories or document names. This would apply to both mike.nd.edu and www.nd.edu and any folders or documents contained under those domains. It would not apply to www.mike.nd.edu because that is a second-level subdomain. A wildcard certificate covering that domain would need to be of the format https://*.mike.nd.edu.
  78. B. Certificate pinning is a control that provides the client browser with instructions about the certificate(s) that it may accept from a specific web server. Certificates not matching the pinned certificate are rejected.
  79. B. The certificate shown here is in ASCII format. The PEM file format is the only answer choice that is an ASCII format. The .DER, .P12, and .PFX certificate files are all binary formats and are not presentable as standard text.
  80. D. The two main properties of any cryptographic cipher are confusion and diffusion. Confusion ensures that the relationship between the cryptographic keys is extremely complex, while diffusion takes any statistical patterns found in the plaintext and prevents them from appearing in the ciphertext. Obfuscation and collusion are not properties of ciphers.
  81. A. The two main properties of any cryptographic cipher are diffusion and confusion. Diffusion takes any statistical patterns found in the plaintext and prevents them from appearing in the ciphertext, while confusion ensures that the relationship between the cryptographic keys is extremely complex. Obfuscation and collusion are not properties of ciphers.