A7011E - Symmetric encryption
Public-key encryption was developed in the late ________
1970s
For a general-purpose block-oriented transmission, you would typically use the ________ mode
CBC
For a general-purpose stream-oriented transmission, you would typically use the ________ mode
CFB
For a stream-oriented transmission over a noisy channel, you would typically use the ________ mode
CTR
________ mode is typically used for a general-purpose block-oriented transmission and is useful for high-speed requirements
CTR
Can turn a block cipher into a stream cipher
However, encryption and decryption cannot be parallelized and random block access is not possible.Output Feedback (OFB)
________ is a term that refers to the means of delivering a key to two parties that wish to exchange data without allowing others to
Key Distribution Technique
The exact substitutions and transformations performed by the algorithm depend on the ________
Secret Key
Each block of plaintext is XORed with an encrypted index
The index is incremented for each subsequent block.Counter (CTR)
Cryptographic systems are generally classified by ________
The type of operations used for transforming plaintext to ciphertext. the number of keys used, the way in which the plaintext is processed
"The plaintext is 64 bits in length and the key is 56 bits in length; longer plaintext amounts are processed in 64-bit blocks" is a description of the DES algorithm[T/F]
True
A brute-force approach involves trying every possible key until an intelligible translation of the ciphertext into plaintext is obtained[T/F]
True
In using encryption, we need to decide what to encrypt and where the encryption gear should be located[T/F]
True
It is possible to convert any block cipher into a stream cipher by using the cipher feedback (CFB) mode [T/F]
True
Key distribution can be achieved for two parties A and B by a third party selecting the key and physically delivering it to A and B[T/F]
True
One desirable property of a stream cipher is that the ciphertext be of the same length as the plaintext[T/F]
True
Symmetric encryption is also referred to as secret-key or single-key encryption[T/F]
True
The National Bureau of Standards is now the National Institute of Standards and Technology[T/F]
True
The ciphertext-only attack is the easiest to defend against[T/F]
True
If the analyst is able to get the source system to insert into the system a message chosen by the analyst, then a ________ attack is possible
Chosen Plaintext
The input to the encryption algorithm is the XOR of the next 64 bits of plaintext and the preceding 64 bits of ciphertext
Cipher Block Chaining (CBC)
The most widely used encryption scheme is based on the ________ adopted in 1977 by the National Bureau of Standards
DES
The ________ is the encryption algorithm run in reverse
Decryption Algorithm
Each block of 64 plaintext bits is encoded independently using the same key
Electronic Code Book (ECB)
"Each block of 64 plaintext bits is encoded independently using the same key" is a description of the CBC mode of operation[T/F]
False
AES uses a Feistel structure[T/F]
False
If both sender and receiver use the same key the system is referred to as asymmetric[T/F]
False
One disadvantage of the link encryption approach is that the message must be decrypted each time it enters a frame switch [T/F]
False
Plaintext is the scrambled message produced as output[T/F]
False
Stream ciphers are far more common than block ciphers[T/F]
False
There are ________ modes of operation defined by NIST that are intended to cover virtually all the possible applications of encryption for which a block cipher could be used
Five
A ________ is a key used between entities for the purpose of distributing session keys
Permanent Key
________ is the original message or data that is fed into the algorithm as input
Plaintext
Input is processed s bits at a time
Preceding ciphertext is used as input to the encryption algorithm to produce pseudorandom output, which is XORed with plaintext to produce the next unit of ciphertext.Cipher Feedback (CFB)
