What is privacy ?
It is to prevent unauthorized persons from extracting information transferred through the channel.
What is authentication ?
It is to prevent unauthorized persons from injecting an unwanted
information into the channel.
What is cryptography ?
It is the transformation of a plain message into an unintelligible one
message (ciphertext).
What is a key ?
It is a set of symbols or characters that determines a specific encryption transformation.
What is cryptanalysis ?
It is an estimation of the plaintext by analyzing the ciphertext in the
channel, without benefit of the key.
What is a cipher brake ?
It is a disclosure of the ciphering algorithm using the cipher-text-
only attack (brute-force) or the known plaintext attack.
What are the two types of cryptography?
Private key and public key.
What is plaintext?
Readable data before encryption.
What is ciphertext?
Encrypted data after encryption.
What key pair does asymmetric cryptography use?
Public key + private key.
Plaintext refers to:
A. The encrypted message
B. The decrypted key
C. The readable original message
D. The hashing output
✅ Answer: C
Ciphertext is:
A. A compressed bitstream
B. Output of source coding
C. A modulated signal
D. Encrypted data
✅ Answer: D
Asymmetric cryptography uses:
A. Two identical keys
B. One key only
C. A public and a private key
D. Three independent keys
✅ Answer: C
A main goal of cryptography listed in the document is:
A. Noise reduction
B. Packet multiplexing
C. Confidentiality
D. Bandwidth optimization
✅ Answer: C
