Certified Encryption Specialist – Questions With
Definitive Solutions
Cryptography Correct Answer - The science of altering communication
so that it cannot be understood without having a key.
Caesar Cipher Correct Answer - Simple cipher that uses shifting letters.
Atbash Correct Answer - Used by Hebrews, cipher that reverses the
alphabet.
ROT13 Correct Answer - Cipher that rotate or shifts by 13 letters.
Scytale Correct Answer - Cylinder tool used to encrypt and decrypt
plaintext using a cloth or piece of leather wrapped around a rod.
Vigenere Cipher Correct Answer - Most common multi-alphabetic
cipher.
Symmetric Encryption Correct Answer - Same key is used to Encrypt
and Decrypt plaintext.
Also known as Single Key Encryption.
Diffusion Correct Answer - Changes to one letter in plaintext changes
multiple characters of the ciphertext.
Confusion Correct Answer - Makes the relationship between the
statistical frequencies of the ciphertext and the actual key as complex as
possible.
Avalanche Correct Answer - A small change in the input yields a large
change in the output.
Complete Avalanche Correct Answer - A change in one bit of the
plaintext affecting all bits in the ciphertext.
Kerckhoffs Principle Correct Answer - The crypto system should be
secure if everything about the system, except the key, is publicly known.
,Substitution Correct Answer - Changing some part of the plaintext for
some matching part of the ciphertext.
Transposition Correct Answer - Swapping of blocks of ciphertext.
Binary ADD Correct Answer - Stack both binary numbers; If both
numbers are 1 then it's 1, otherwise it's 0.
Binary OR Correct Answer - Stack both binary numbers; If either is a 1
then it's 1, otherwise it's 0.
Binary XOR Correct Answer - Stack both binary numbers; If their is a 1 in
one number but not the other then it's a 1, otherwise its 0.
This is reversible.
Block Cipher Correct Answer - Encrypts the information in blocks.
Stream Cipher Correct Answer - Encrypts the information one bit at a
time.
DES Correct Answer - Data Encryption Standard
DES (Characteristics) Correct Answer - Made by IBM in 1970's.
64 bit Block Cipher.
56 Bit Key.
Uses Feistal Cipher.
Feistal Function Correct Answer - 64 Bits split Left and Right, Round
function to one side, XORed with the other side then sides are Transposed or
switched.
Then continued for a set number of rounds.
Unbalanced Feistal Function Correct Answer - Same as Feistal but the 64
bits are not equally split.
Skipjack uses the Unbalanced Feistal Function.
, 3DES Correct Answer - Uses Data Encryption Standard with a key
bundle. Three 56 bit keys are used to encrypt with key 1, decrypt with key 2
and then encrypt with key 3.
DESx Correct Answer - Same as Data Encryption Standard but the
plaintext is XORed with the key then encrypted.
Is not more secure since the key space is still the same.
Whitening Correct Answer - The process of XORing in an additional key
at any time in the encryption process.
AES Correct Answer - Advanced Encryption Standard
AES (Characteristics) Correct Answer - Replaced DES in 2001.
Capable of Key sizes 128 bit, 192 bit, and 256 bit.
128 bit Block Size.
Developed by Joan Daemen and Vincent Rimen.
Designated as FIPS 197.
Based on substitution-permutation matrix.
Blowfish (Characteristics) Correct Answer - Capable of Key sizes 32 to
448 bits.
64 bit Block Size.
Developed by Bruce Schneier.
Based on Feistal Cipher using 16 rounds.
Serpent (Characteristics) Correct Answer - Capable of Key sizes 128 bit,
192 bit, and 256 bit.
128 bit Block Size.
Developed by Ross Anderson, Eli Biham, and Lars Knudson.
Based on substitution-permutation similar to AES
Designed to execute all operations in parallel.
Twofish (Characteristics) Correct Answer - Capable of Key sizes up to
256 bits.
128 bit Block Size.
Developed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris
Hall, and Neils Ferguson.
Definitive Solutions
Cryptography Correct Answer - The science of altering communication
so that it cannot be understood without having a key.
Caesar Cipher Correct Answer - Simple cipher that uses shifting letters.
Atbash Correct Answer - Used by Hebrews, cipher that reverses the
alphabet.
ROT13 Correct Answer - Cipher that rotate or shifts by 13 letters.
Scytale Correct Answer - Cylinder tool used to encrypt and decrypt
plaintext using a cloth or piece of leather wrapped around a rod.
Vigenere Cipher Correct Answer - Most common multi-alphabetic
cipher.
Symmetric Encryption Correct Answer - Same key is used to Encrypt
and Decrypt plaintext.
Also known as Single Key Encryption.
Diffusion Correct Answer - Changes to one letter in plaintext changes
multiple characters of the ciphertext.
Confusion Correct Answer - Makes the relationship between the
statistical frequencies of the ciphertext and the actual key as complex as
possible.
Avalanche Correct Answer - A small change in the input yields a large
change in the output.
Complete Avalanche Correct Answer - A change in one bit of the
plaintext affecting all bits in the ciphertext.
Kerckhoffs Principle Correct Answer - The crypto system should be
secure if everything about the system, except the key, is publicly known.
,Substitution Correct Answer - Changing some part of the plaintext for
some matching part of the ciphertext.
Transposition Correct Answer - Swapping of blocks of ciphertext.
Binary ADD Correct Answer - Stack both binary numbers; If both
numbers are 1 then it's 1, otherwise it's 0.
Binary OR Correct Answer - Stack both binary numbers; If either is a 1
then it's 1, otherwise it's 0.
Binary XOR Correct Answer - Stack both binary numbers; If their is a 1 in
one number but not the other then it's a 1, otherwise its 0.
This is reversible.
Block Cipher Correct Answer - Encrypts the information in blocks.
Stream Cipher Correct Answer - Encrypts the information one bit at a
time.
DES Correct Answer - Data Encryption Standard
DES (Characteristics) Correct Answer - Made by IBM in 1970's.
64 bit Block Cipher.
56 Bit Key.
Uses Feistal Cipher.
Feistal Function Correct Answer - 64 Bits split Left and Right, Round
function to one side, XORed with the other side then sides are Transposed or
switched.
Then continued for a set number of rounds.
Unbalanced Feistal Function Correct Answer - Same as Feistal but the 64
bits are not equally split.
Skipjack uses the Unbalanced Feistal Function.
, 3DES Correct Answer - Uses Data Encryption Standard with a key
bundle. Three 56 bit keys are used to encrypt with key 1, decrypt with key 2
and then encrypt with key 3.
DESx Correct Answer - Same as Data Encryption Standard but the
plaintext is XORed with the key then encrypted.
Is not more secure since the key space is still the same.
Whitening Correct Answer - The process of XORing in an additional key
at any time in the encryption process.
AES Correct Answer - Advanced Encryption Standard
AES (Characteristics) Correct Answer - Replaced DES in 2001.
Capable of Key sizes 128 bit, 192 bit, and 256 bit.
128 bit Block Size.
Developed by Joan Daemen and Vincent Rimen.
Designated as FIPS 197.
Based on substitution-permutation matrix.
Blowfish (Characteristics) Correct Answer - Capable of Key sizes 32 to
448 bits.
64 bit Block Size.
Developed by Bruce Schneier.
Based on Feistal Cipher using 16 rounds.
Serpent (Characteristics) Correct Answer - Capable of Key sizes 128 bit,
192 bit, and 256 bit.
128 bit Block Size.
Developed by Ross Anderson, Eli Biham, and Lars Knudson.
Based on substitution-permutation similar to AES
Designed to execute all operations in parallel.
Twofish (Characteristics) Correct Answer - Capable of Key sizes up to
256 bits.
128 bit Block Size.
Developed by Bruce Schneier, John Kelsey, Doug Whiting, David Wagner, Chris
Hall, and Neils Ferguson.
