Chapter 6 Cryptography and Symmetric Key Algorithms Flashcards
To encrypt a message, you simply shift each letter of the alphabet three places to the
right
Caesar cipher r .
a cryptographic system should be secure
even if everything about the system, except the key, is public knowledge.
The Kerchoff Principle
random number that acts as a placeholder variable in mathematical functions.
nonce
Zero-Knowledge Proof
zero-knowledge proof
When the information or privilege required to perform an operation is divided among
multiple users, no single person has suffi cient privileges to compromise the security
of an environment.
Split Knowledge
a minimum number of agents out of the total number of agents work together to perform high-security tasks.
M of N Control
cryptographic systems of symbols that represent words or phrases,
Codes
always meant to hide the true meaning of a message
Ciphers
________ use an encryption algorithm to rearrange the letters of a plaintext message, forming the ciphertext message.
Transposition ciphers
use a different substitution alphabet for each letter of the plaintext message.
one-time pad
the encryption key is as long as the m r essage itself and is often
chosen from a common book
running key cipher
the relationship between the plain text
and the key is so complicated that an attacker can’t merely continue altering the plain
text and analyzing the resulting ciphertext to determine the key.
Confusion
a change in the plain text results in multiple changes spread throughout the ciphertext.
Diffusion
Advanced Encryption Standard (AES)
Block Size____ bits
Key Size _____ bits
Block Size - 128
Key size - 128, 192, 256
Skipjack
Block Size____ bits
Key Size _____ bits
Block Size 64
Key size 80
IDEA (used in PGP)
Block Size____ bits
Key Size _____ bits
Block size 64
Key size 128
Twofish
Block Size____ bits
Key Size _____ bits
Block size 128
Key size 1 - 256
DES
Block Size____ bits
Key Size _____ bits
Block size 64
Key size 56
Triple DES (3DES)
Block Size____ bits
Key Size _____ bits
Block size 64
Key size 168
_______ was developed in response to complaints about the insufficient key length of the DES algorithm.
International Data Encryption Algorithm (IDEA)
International Data Encryption Algorithm key is broken up in a series of operations into __ 16-bit subkeys.
52
Which algorithm supports the escrow of encryption keys ?
Rijndael
Twofish
Skipjack
Blowfish
Skipjack
Twofish uses two techniques not found in other algorithms
Prewhitening
Postwhitening
Involves XORing the plain text with a separate subkey before the first round of encryption.
Prewhitening
Postwhitening
Prewhitening
Involves XORing the plain text with a separate subkey after the 16th round of encryption.
Postwhitening
Name the three main methods used to exchange secret keys securely.
Diffie-Hellman, Public Key Encryption, Offline Distribution
Name two major approaches to key escrow that have been proposed over the past decade:
Fair Cryptosystems, Escrowed Encryption Standard
In this escrow approach, the secret keys used in a communication are divided into two or more pieces, each of which is given to an independent third party.
Each of these pieces is useless on its own but may be recombined to obtain the secret key.
Fair Cryptosystems
Escrowed Encryption Standard
Fair Cryptosystems
This escrow approach provides the government with a technological means to decrypt ciphertext. This standard is the basis behind the Skipjack algorithm.
Fair Cryptosystems
Escrowed Encryption Standard
Escrowed Encryption Standard
Name 6 symmetric algorithms
Data Encryption Standard (DES) Triple DES (3DES) International Data Encryption Algorithm (IDEA) Blowfish Skipjack, Advanced Encryption Standard (AES).
