Chapter 9

Encryption can help protect volumes in all of the following situations, except:

b) to prevent physical damage to a hard drive.

c) when an eavesdropper looks at the volume without the operating system in place.

d) when discarding a hard drive or other device without wiping it.

a) when a storage device is lost or stolen.

b) to prevent physical damage to a hard drive.

Access control protects data on a computer against:

d) recycling.

c) hostile users.

a) Trojans.

b) theft.

c) hostile users.

File encryption protects data on a computer against all of the following, except:

a) hostile users.

d) theft.

c) Trojan crypto.

b) Trojans.

c) Trojan crypto.

Volume encryption protects data on a computer against:

d) theft.

a) hostile users.

b) Trojans.

c) Trojan crypto.

d) theft.

Alice is using volume encryption on her laptop. Which of the following attacks are blocked by volume encryption, instead of other techniques, like file encryption or access controls? Select all that apply.

b) Someone steals Alice's laptop.

c) Kevin gives Alice a program with a Trojan horse that steals sensitive files from her and emails them to him.

d) Alice's cousin borrows her laptop.

a) Alice forgets to explicitly encrypt a sensitive file.

b) Someone steals Alice's laptop.a) Alice forgets to explicitly encrypt a sensitive file.

Alice is using file encryption on her laptop. Which of the following attacks are blocked by file encryption, instead of other techniques, like volume encryption or access controls?

c) Kevin gives Alice a program with a Trojan horse that steals sensitive files from her and emails them to him.

a) Alice forgets to explicitly encrypt a sensitive file.

b) Someone steals Alice's laptop.

d) Alice's cousin borrows her laptop.

c) Kevin gives Alice a program with a Trojan horse that steals sensitive files from her and emails them to him.

b) Someone steals Alice's laptop.

When encrypting data with a block cipher, each repetition is called a:

a) round.

c) key expansion.

d) run.

b) key schedule.

a) round.

The following are all best practices or proper recommendations for choosing an encryption algorithm, except:

b) use DES if at all possible.

a) use evaluated cryptographic products if using a certified algorithm.

d) check recent news and research results in the crypto community.

c) do not use "private label" algorithms that have not been published and reviewed by the cryptographic community.

b) use DES if at all possible.

Select the technical features of DES from the following list:

64

56

Originally, but no longer

- - - - -

Is this a U.S government standard?

Block size

Key size

64 - block size

56 - key size

originally, but no longer - Is this a U.S. government standard?

Select the technical features of Lucifer from the following list:

64

128

No

- - - - -

Is this a U.S government standard?

Block size

Key size

64 - Block size

128 - key size

No - is this a U.S government standards?

Select the technical features of Lucifer from the following list:

128

128, 192, 256

Yes

- - - - -

Is this a U.S government standard?

Block size

Key size

128 - Block size

128, 192, 256 - Key size

Yes - Is this a U.S government standard?

A block cipher algorithm operates more slowly if we change the key every time we use it. Which of the following concepts is most responsible for this delay?

c) S-boxes

a) Key expansion

b) Rounds

d) Permutations

a) Key expansion

Bob needs to deploy an efficient block cipher. He has a choice between 128-bit AES and Triple DES using three different keys. Which of the following statements is most accurate about these choices?b) Triple DES is more efficient than AES and it provides better security.

a) AES is more efficient than triple DES and it provides better security.

d) Triple DES is more efficient than AES, but AES provides better security.

c) AES is more efficient than triple DES, but triple DES provides better security.

a) AES is more efficient than triple DES and it provides better security.

True or False? S-boxes are special data structures that control substitutions in block ciphers.

True

Which of the following qualities of a good encryption algorithm apply to DES today? Select all that apply.

b) Security does not rely on its secrecy

d) Subjected to analysis

e) No practical weaknesses

c) Available for analysis

a) Explicitly designed for encryption

b) Security does not rely on its secrecy

d) Subjected to analysis

c) Available for analysis

a) Explicitly designed for encryption

Which of the following qualities of a good encryption algorithm apply to AES today? Select all that apply.

b) Security does not rely on its secrecy

d) Subjected to analysis

e) No practical weaknesses

c) Available for analysis

a) Explicitly designed for encryption

b) Security does not rely on its secrecy

d) Subjected to analysis

e) No practical weaknesses

c) Available for analysis

a) Explicitly designed for encryption

In the 1970s, the _________ was the only organization in the U.S. government with cryptographic expertise.

d) DHS

a) CIA

c) FBI

b) NSA

b) NSA

Which of the following key sizes are supported by Triple DES? Select all that apply.

e) 168

g) 256

a) 56

c) 112

b) 64

f) 192

d) 128

e) 168

a) 56

c) 112

Which of the following are true about the development of AES? Select all that apply.

e) The rationale for the algorithm design was kept secret.

f) The U.S. government adopted the algorithm as an official federal standard for encryption.

b) The algorithm was chosen from a group of candidates.

c) The algorithm was chosen based on published criteria.

a) The algorithm was officially published to allow its general-purpose use.

d) The algorithm was chosen by comparing it to other algorithms.

f) The U.S. government adopted the algorithm as an official federal standard for encryption.

b) The algorithm was chosen from a group of candidates.

c) The algorithm was chosen based on published criteria.

a) The algorithm was officially published to allow its general-purpose use.

d) The algorithm was chosen by comparing it to other algorithms.

True or False? The underlying code of the Rijndael algorithm was leaked to the public in 1994, allowing for successful attacks against data encrypted with Rijndael.

False

Which of the following are true about the development of RC4? Select all that apply.

a) The algorithm was officially published to allow its general-purpose use.

e) The rationale for the algorithm design was kept secret.

b) The algorithm was chosen from a group of candidates.

f) The U.S. government adopted the algorithm as an official federal standard for encryption.

c) The algorithm was chosen based on published criteria.

d) The algorithm was chosen by comparing it to other algorithms.

e) The rationale for the algorithm design was kept secret.

The phrases below describe properties or functions of encryption technologies. Match the type of encryption with its property or function.

DES

-Each encryption operation may use a separate 56-bit key

-The principal weakness is its key size

-Performs 10 rounds when encrypting with a 128-bit key

The principal weakness is its key size

The phrases below describe properties or functions of encryption technologies. Match the type of encryption with its property or function.

Triple DES

-Each encryption operation may use a separate 56-bit key

-The principal weakness is its key size

-Performs 10 rounds when encrypting with a 128-bit key

Each encryption operation may use a separate 56-bit key

The phrases below describe properties or functions of encryption technologies. Match the type of encryption with its property or function.

Rijndael

-Each encryption operation may use a separate 56-bit key

-The principal weakness is its key size

-Performs 10 rounds when encrypting with a 128-bit key

Performs 10 rounds when encrypting with a 128-bit key

We receive several blocks of ciphertext in ECB mode. An error has changed a single bit in the middle of the ciphertext. How much of the plaintext will be affected by the error when we decrypt it?

a) One bit

b) One block

d) All plaintext following the error in the ciphertext

c) One bit and one block

b) One block

Here is a list of features of a block cipher mode. Select all that apply to the CBC mode.

a) Ciphertext must fit into a multiple of the cipher's block size; it can't be an arbitrary number of bits.

f) The mode uses both the block cipher algorithm and the XOR operation.

c) The key provided to the block cipher varies according to the ciphertext.

b) The key provided to the block cipher varies according to the plaintext.

d) The mode requires an initialization vector.

e) The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.

a) Ciphertext must fit into a multiple of the cipher's block size; it can't be an arbitrary number of bits.

f) The mode uses both the block cipher algorithm and the XOR operation.

d) The mode requires an initialization vector.

Here is a list of features of a block cipher mode. Select all that apply to the CTR mode.

f) The mode uses both the block cipher algorithm and the XOR operation.

a) Ciphertext must fit into a multiple of the cipher's block size; it can't be an arbitrary number of bits.

b) The key provided to the block cipher varies according to the plaintext.

c) The key provided to the block cipher varies according to the ciphertext.

e) The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.

d) The mode requires an initialization vector.

f) The mode uses both the block cipher algorithm and the XOR operation.

e) The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.

d) The mode requires an initialization vector.

Here is a list of features of a block cipher mode. Select all that apply to the OFB mode.

b) The key provided to the block cipher varies according to the plaintext.

d) The mode requires an initialization vector.

a) Ciphertext must fit into a multiple of the cipher's block size; it can't be an arbitrary number of bits.

c) The key provided to the block cipher varies according to the ciphertext.

f) The mode uses both the block cipher algorithm and the XOR operation.

e) The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.

d) The mode requires an initialization vector.

f) The mode uses both the block cipher algorithm and the XOR operation.

e) The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.

True or False? Changing a single bit of a block cipher's input affects the entire output block.

True

An initialization vector is most similar to which of the following?

b) Secret key

c) Hash value

a) Nonce

d) Plaintext

e) Ciphertext

a) Nonce

We receive several blocks of ciphertext in OFB mode. An error has changed a single bit in the middle of the ciphertext. How much of the plaintext will be affected by the error when we decrypt it?

a) One bit

d) All plaintext following the error in the ciphertext

b) One block

c) One bit and one block

a) One bit

We receive several blocks of ciphertext in CTR mode. An error has changed a single bit in the middle of the ciphertext. How much of the plaintext will be affected by the error when we decrypt it?

a) One bit

c) One bit and one block

b) One block

d) All plaintext following the error in the ciphertext

a) One bit

We receive several blocks of ciphertext in CFB mode. An error has changed a single bit in the middle of the ciphertext. How much of the plaintext will be affected by the error when we decrypt it?

b) One block

c) One bit and one block

d) All plaintext following the error in the ciphertext

a) One bit

c) One bit and one block

We receive several blocks of ciphertext in CBC mode. An error has changed a single bit in the middle of the ciphertext. How much of the plaintext will be affected by the error when we decrypt it?

b) One block

c) One bit and one block

d) All plaintext following the error in the ciphertext

a) One bit

c) One bit and one block

True or False? Cipher block chaining (CBC) is a widely used cipher mode that requires plaintext to be a multiple of the cipher's block size.

True

True or False? A tweakable cipher includes a third input, a nonce-like value that modifies the encryption without the cost of changing the encryption key.

True

We have an operating system that includes built-in file encryption. When we consider the layers of system software, where does the file encryption reside?

d) Between the device driver and its device

b) Between the file system and the device driver

c) Above the application layer

a) Between the file system and the application layer.

a) Between the file system and the application layer.

Bob is creating his own volume encryption mechanism. He is building a cipher mode that works as follows:• The mode uses the block cipher encryption and decryption in ECB mode.• There is no initialization vector.To "tweak" the cipher, Bob varies the secret key used during encryption. For example, the third block of sector 12345 would be combined with the secret value 77777777 to create the following secret key for the block cipher: 7777777712345003. Is this a good idea or a bad idea?

d) It is a good idea because a disk block error only affects a small part of the disk block.

a) It is a bad idea because the cipher must redo its key scheduling for every block.

b) It is a bad idea because the cipher must execute additional rounds to handle the different keys.

c) It is a good idea because it eliminates the initialization vector.

a) It is a bad idea because the cipher must redo its key scheduling for every block.

We are implementing volume encryption using ESSIV mode, as discussed in Section 9.4.2. Which of the following statements are true about the implementation? Select all that apply.

c) All sectors use the same block cipher key.

a) The mode uses sector numbers to vary the information in the ciphertext.

e) Sectors are vulnerable to bit-flipping attacks.

b) Different initialization vectors are stored in different disk sectors.

d) The decryption process never uses block decryption.

c) All sectors use the same block cipher key.

a) The mode uses sector numbers to vary the information in the ciphertext.

We are implementing volume encryption using counter mode, as discussed in Section 9.4.2. Which of the following statements are true about the implementation? Select all that apply.

d) The decryption process never uses block decryption.

a) The mode uses sector numbers to vary the information in the ciphertext.

b) Different initialization vectors are stored in different disk sectors.

c) All sectors use the same block cipher key.

e) Sectors are vulnerable to bit-flipping attacks.

d) The decryption process never uses block decryption.

a) The mode uses sector numbers to vary the information in the ciphertext.

c) All sectors use the same block cipher key.

e) Sectors are vulnerable to bit-flipping attacks.

We are encrypting a volume using CTR mode as described in Section 9.4.2. Given the ciphertext changes and results listed below, which will occur in CTR mode? Select all that apply.

c) If we rewrite the entire sector with a previous version of its contents, the sector will decrypt correctly.

b) If we swap two data blocks on the sector, the only plaintext affected are from those two data blocks.

a) A bit-flipping attack only affects the single modified bit in the plaintext block.

c) If we rewrite the entire sector with a previous version of its contents, the sector will decrypt correctly.

b) If we swap two data blocks on the sector, the only plaintext affected are from those two data blocks.

a) A bit-flipping attack only affects the single modified bit in the plaintext block.

We are implementing volume encryption using XTS mode, as discussed in Section 9.4.3. Which of the following statements are true about the

implementation? Select all that apply.

b) Different initialization vectors are stored in different disk sectors.

d) The decryption process never uses block decryption.

e) Sectors are vulnerable to bit-flipping attacks.

c) All sectors use the same block cipher key.

a) The mode uses sector numbers to vary the information in the ciphertext.

c) All sectors use the same block cipher key.

a) The mode uses sector numbers to vary the information in the ciphertext.

We are encrypting a volume using XTS mode as described in Section 9.4.3. Given the ciphertext changes and results listed below, which will occur in XTS mode? Select all that apply.

a) A bit-flipping attack only affects the single modified bit in the plaintext block.

c) If we rewrite the entire sector with a previous version of its contents, the sector will decrypt correctly.

b) If we swap two data blocks on the sector, the only plaintext affected are from those two data blocks.

c) If we rewrite the entire sector with a previous version of its contents, the sector will decrypt correctly.

b) If we swap two data blocks on the sector, the only plaintext affected are from those two data blocks.

We reduce the risk of untrustworthy encryption by using certified products. In the

b) 142-1.

c) 140-2.

United States, the recognized certification is FIPS:

d) 160-8.

a) 140-4.

c) 140-2.

We have implemented volume encryption using a self-encrypting drive. Which of the following attacks is the volume still vulnerable to? Select all that apply.

b) Trojan BIOS intercepting the unlock code when the operator unlocks the drive

a) Drive theft

c) Trojan software in the OS that sniffs the working key while the volume is unlocked

d) Hostile users sharing the OS

b) Trojan BIOS intercepting the unlock code when the operator unlocks the drive

Why should a self-encrypting hard drive wrap its working keys when the drive is locked?

d) It allows the owner to make a back-up of the working key.

a) It allows the drive to reboot automatically if being used with a high-availability server.

c) It supports pre-boot authentication.

b) It protects the key from electronic probing and extraction even if the drive is powered off.

b) It protects the key from electronic probing and extraction even if the drive is powered off.

In 2008, researchers at Princeton University demonstrated techniques to retrieve RAM contents after the computer had been powered off. They then extracted drive encryption keys from RAM and used them to decrypt an encrypted drive. This is called a(n):

d) cold-boot attack.

b) eavesdrop attack.

a) master key attack.

c) swap attack.

d) cold-boot attack.

Which of the following are practical risks that apply to software-based volume encryption systems? Select all that apply.

a) Offline cracking of wrapped keys

d) Retrieve working key from saved RAM when the system hibernates

e) Intercept a passphrase that unlocks the encrypted drive

c) Trial-and-error guessing of a working key

b) Online eavesdropping on a software encryption process

a) Offline cracking of wrapped keys

d) Retrieve working key from saved RAM when the system hibernates

e) Intercept a passphrase that unlocks the encrypted drive

b) Online eavesdropping on a software encryption process

Which of the following are practical risks that apply to hardware-based volume encryption systems? Select all that apply.

e) Intercept a passphrase that unlocks the encrypted drive

d) Retrieve working key from saved RAM when the system hibernates

a) Offline cracking of wrapped keys

c) Trial-and-error guessing of a working key

b) Online eavesdropping on a software encryption process

e) Intercept a passphrase that unlocks the encrypted drive

a) Offline cracking of wrapped keys

Which of the following might be considered an antitamper technique? Select all that apply.

b) Storing a working key in nonvolatile memory

d) Storing wrapped keys on a DVD and using those keys to unwrap other keys on the disk

c) Sensing attempts to disassemble the device during operation, and erasing working keys if such attempts are detected

a) Encapsulating the crypto key storage and its related logic in plastic

c) Sensing attempts to disassemble the device during operation, and erasing working keys if such attempts are detected

a) Encapsulating the crypto key storage and its related logic in plastic

Bob has purchased a self-encrypting hard drive that always encrypts everything stored on the drive. Bob wants to install a bootable operating system on it and use it on an older computer. The old computer does not allow him to install pre-boot authentication in the BIOS. Will he be able to use the drive?

d) No, because there is no way to add a plaintext partition to this drive.

b) Yes, because he can run an application on his operating system that unlocks the drive.

c) No, because a separate drive partition is only used in software-based drive encryption systems.

a) Yes, because he can add a plaintext partition to the drive and install the pre-boot authentication software on that partition.

d) No, because there is no way to add a plaintext partition to this drive.

The phrases below describe risks involved with full-drive encryption keys. Match the risk with its description or method.

Eavesdrop on a software encryption process

-A computer process "listens" to the encryption or decryption process and sniffs the key schedule

-Key schedule and possibly the key are extracted from paging file after RAM is written to the hard drive

-Extract keys from cooled RAM chips

A computer process "listens" to the encryption or decryption process and sniffs the key schedule

The phrases below describe risks involved with full-drive encryption keys. Match the risk with its description or method.

Scavenge keys from swap files

-A computer process "listens" to the encryption or decryption process and sniffs the key schedule

-Key schedule and possibly the key are extracted from paging file after RAM is written to the hard drive

-Extract keys from cooled RAM chips

Key schedule and possibly the key are extracted from paging file after RAM is written to the hard drive

The phrases below describe risks involved with full-drive encryption keys. Match the risk with its description or method.

Scavenge keys from powered-off RAM

-A computer process "listens" to the encryption or decryption process and sniffs the key schedule

-Key schedule and possibly the key are extracted from paging file after RAM is written to the hard drive

-Extract keys from cooled RAM chips

Extract keys from cooled RAM chips