E CES 212 81 Actual Questions and Correct Answers
Q1
The same key is used to encrypt and decrypt the message, faster than asymmetric but have an
issue with key exchange
Answer: Symmetric Key Cryptography
Q2
Modern cryptography began in 1949 when Claude Shannon published a paper about the
Mathematical Theory of Communication. This idea improved cryptography.
Answer: Information Theory
Q3
Changes to one character in the plain text affect multiple characters in the cipher text, unlike in
historical algorithms where each plain text character only affect one cipher text character.
Answer: Diffusion
Q4
Occurs by using a complex substitution algorithm. Attempts to make the relationship between
the statistical frequencies of the cipher text and the key as complex as possible.
Answer: Confusion
Q5
A desirable effect where a change to one bit leads to large change in output. This is Fiestel's
take on Claude Shannon's concept of diffusion. Fiestel's ideas are important when discussing
block ciphers.
Answer: Avalanche
Q6
A cryptosystem should be secure, even if everything about the system is publicly known.
Answer: Kerckhoff's Principle
, Q7
C=E(k,p) Cipher Text ( C) is equal to the encryption function ( E) with the key (k) and plain text
(p) being passed as parameters to that function.
Answer: How symmetric algorithm encryption is expressed mathematically
Q8
P=D(k,c) The plain text (P) is equal to the encryption function (E) with the key (k) and the cipher
text (c) being passed as parameters to that function.
Answer: How symmetric algorithm decryption is expressed mathematically
Q9
Substitution and Transposition
Answer: Two things all modern block cipher algorithms use
Q10
Asks if there is a one in both the first and second number. Numbers are compared one digit at a
time. Example: Number A 1101 Number B 0110 returns a result of Number C 0100 Binary AND
Answer: compared one digit at a time.
Q11
Asks if there is a one in the first number, or the second, or in both numbers. Each place is
compared one at a time. Example: Number A 1101 Number B 1001 returns a result of Number C
1101 Binary OR
Answer: Example:
Q12
Important because it reversible. Asks if there is a 1 in one of the numbers but not both. Each
place is compared one at a time. To reverse XOR your result back with your second number and
you will get the first number. Example: Number A 1101 Number B 0110 returns a result of
Number C 1011
Answer: Binary XOR (exclusive OR)
Q13
Block Ciphers and Stream Ciphers
Answer: Two types of symmetric algorithms
Q1
The same key is used to encrypt and decrypt the message, faster than asymmetric but have an
issue with key exchange
Answer: Symmetric Key Cryptography
Q2
Modern cryptography began in 1949 when Claude Shannon published a paper about the
Mathematical Theory of Communication. This idea improved cryptography.
Answer: Information Theory
Q3
Changes to one character in the plain text affect multiple characters in the cipher text, unlike in
historical algorithms where each plain text character only affect one cipher text character.
Answer: Diffusion
Q4
Occurs by using a complex substitution algorithm. Attempts to make the relationship between
the statistical frequencies of the cipher text and the key as complex as possible.
Answer: Confusion
Q5
A desirable effect where a change to one bit leads to large change in output. This is Fiestel's
take on Claude Shannon's concept of diffusion. Fiestel's ideas are important when discussing
block ciphers.
Answer: Avalanche
Q6
A cryptosystem should be secure, even if everything about the system is publicly known.
Answer: Kerckhoff's Principle
, Q7
C=E(k,p) Cipher Text ( C) is equal to the encryption function ( E) with the key (k) and plain text
(p) being passed as parameters to that function.
Answer: How symmetric algorithm encryption is expressed mathematically
Q8
P=D(k,c) The plain text (P) is equal to the encryption function (E) with the key (k) and the cipher
text (c) being passed as parameters to that function.
Answer: How symmetric algorithm decryption is expressed mathematically
Q9
Substitution and Transposition
Answer: Two things all modern block cipher algorithms use
Q10
Asks if there is a one in both the first and second number. Numbers are compared one digit at a
time. Example: Number A 1101 Number B 0110 returns a result of Number C 0100 Binary AND
Answer: compared one digit at a time.
Q11
Asks if there is a one in the first number, or the second, or in both numbers. Each place is
compared one at a time. Example: Number A 1101 Number B 1001 returns a result of Number C
1101 Binary OR
Answer: Example:
Q12
Important because it reversible. Asks if there is a 1 in one of the numbers but not both. Each
place is compared one at a time. To reverse XOR your result back with your second number and
you will get the first number. Example: Number A 1101 Number B 0110 returns a result of
Number C 1011
Answer: Binary XOR (exclusive OR)
Q13
Block Ciphers and Stream Ciphers
Answer: Two types of symmetric algorithms
