025/2026 WGU D334 EXAM WITH Q&A
2
ACCURATE ANSWERS
CB (Electronic Code Book)
E
Simplest mode:Encrypts each block of plaintext independentlyusing the same key.
Weakness:Identical plaintext blocks produce identicalciphertext, making it vulnerable
to copy-paste attacks.
Not recommended for sensitive data.
BC (Cipher Block Chaining)
C
Adds dependency:Each plaintext block is XORed withthe ciphertext of the previous
block before encryption.
Initialization Vector (IV):A random value used toencrypt the first block, ensuring
ciphertext variation even with identical plaintext.
Strength:More secure than ECB, mitigates copy-pasteattacks.
Important Note:The IV needs to be transmitted with the ciphertext for decryption.
FB (Cipher Feedback)
C
Self-synchronizing stream cipher:Turns a block cipherinto a stream cipher,
encrypting data one bit/byte at a time.
Process:The IV is encrypted, and the output is XORedwith the plaintext to generate
ciphertext. A portion of tHUMAN COMPREHENSIVE HEAD TO TOE LAURA WOODhe
XOR output becomes the new IV for the next block.
Advantage:Errors in transmission only affect a limited portion of the data stream.
FB (Output Feedback)
O
Similar to CFB:Also a self-synchronizing stream cipher.
Difference:Uses the output of the encryption stage (before XOR) as the next IV.
Advantage:Pre-computation of keystream is possible, leading to faster
encryption/decryption
TR (Counter)
C
Transforms block cipher to stream cipher:Uses a countervalue and a nonce
(unique number) to generate a keystream.
Process:Each block is encrypted independently usinga unique counter value, enabling
parallel processing.
Advantages:High performance, random access to encrypted data, and efficient error
handling.
, GP (Pretty Good Privacy)
P
Pretty Good Privacy allows users to send encrypted and authenticated emails.
Stream Encryption
Data stream where one bit at a time is encrypted.
Faster than block encryption and used for real-time applications.
Examples: RC4, CHACHA
Block Encryption
Encrypt data in fixed-size blocks such as 128-bits and 192-bits.
Used for data-at-rest, file encryption, and data communication.
Block Encryption Algos
Memory help for symmetric examples: C32BRAIDSXS
Camellia
3DES
2fish (Twofish)
Blowfish
RC2,5,6
AES
IDEA
DES
XTEA
Skipjack
Block Encryption Modes
ECB
CBC
CFB
OFB
CTR
IV (Initialization Vector)
A random value/seed. Typically added to the ciphering process so it changes from block
to block (block encryption) or frame to frame (steam encryption).
Substitution
A process of replacing one value with another value based on a predefined mapping or
a lookup table.This technique is used in the AdvancedEncryption Standard (AES) with
a component called the substitution bytes or S-box.
Transformation
Aims to enhance the security of data by making the relationship between the input
(plaintext) and output (ciphertext) more complex. The sources describe two main types
of transformation: substitution and diffusion.
Diffusion
2
ACCURATE ANSWERS
CB (Electronic Code Book)
E
Simplest mode:Encrypts each block of plaintext independentlyusing the same key.
Weakness:Identical plaintext blocks produce identicalciphertext, making it vulnerable
to copy-paste attacks.
Not recommended for sensitive data.
BC (Cipher Block Chaining)
C
Adds dependency:Each plaintext block is XORed withthe ciphertext of the previous
block before encryption.
Initialization Vector (IV):A random value used toencrypt the first block, ensuring
ciphertext variation even with identical plaintext.
Strength:More secure than ECB, mitigates copy-pasteattacks.
Important Note:The IV needs to be transmitted with the ciphertext for decryption.
FB (Cipher Feedback)
C
Self-synchronizing stream cipher:Turns a block cipherinto a stream cipher,
encrypting data one bit/byte at a time.
Process:The IV is encrypted, and the output is XORedwith the plaintext to generate
ciphertext. A portion of tHUMAN COMPREHENSIVE HEAD TO TOE LAURA WOODhe
XOR output becomes the new IV for the next block.
Advantage:Errors in transmission only affect a limited portion of the data stream.
FB (Output Feedback)
O
Similar to CFB:Also a self-synchronizing stream cipher.
Difference:Uses the output of the encryption stage (before XOR) as the next IV.
Advantage:Pre-computation of keystream is possible, leading to faster
encryption/decryption
TR (Counter)
C
Transforms block cipher to stream cipher:Uses a countervalue and a nonce
(unique number) to generate a keystream.
Process:Each block is encrypted independently usinga unique counter value, enabling
parallel processing.
Advantages:High performance, random access to encrypted data, and efficient error
handling.
, GP (Pretty Good Privacy)
P
Pretty Good Privacy allows users to send encrypted and authenticated emails.
Stream Encryption
Data stream where one bit at a time is encrypted.
Faster than block encryption and used for real-time applications.
Examples: RC4, CHACHA
Block Encryption
Encrypt data in fixed-size blocks such as 128-bits and 192-bits.
Used for data-at-rest, file encryption, and data communication.
Block Encryption Algos
Memory help for symmetric examples: C32BRAIDSXS
Camellia
3DES
2fish (Twofish)
Blowfish
RC2,5,6
AES
IDEA
DES
XTEA
Skipjack
Block Encryption Modes
ECB
CBC
CFB
OFB
CTR
IV (Initialization Vector)
A random value/seed. Typically added to the ciphering process so it changes from block
to block (block encryption) or frame to frame (steam encryption).
Substitution
A process of replacing one value with another value based on a predefined mapping or
a lookup table.This technique is used in the AdvancedEncryption Standard (AES) with
a component called the substitution bytes or S-box.
Transformation
Aims to enhance the security of data by making the relationship between the input
(plaintext) and output (ciphertext) more complex. The sources describe two main types
of transformation: substitution and diffusion.
Diffusion
