EC Council CES Flash Cards Exam Questions with Correct Answers Latest Update 2025/2026
Atbash Cipher - Answers Invented by the Hebrew. Single substitution monoalphabetic cipher
that substitutes each letter with it's reverse (a and z, b and y, etc).
Caesar Cipher - Answers Monoalphabetic cipher where letters are shifted one or more letters in
either direction.
ROT 13 - Answers Monoalphabetic cipher that shifts characters 13 characters. Stands for
Rotate 13. A would become N, B would become O, etc.
Scytale Cipher - Answers Was a staff with papyrus or letter wrapped around it so edges would
line up. There would be a stream of characters which would show you your message. When
unwound it would be a random string of characters. Would need an identical size staff on other
end for other individuals to decode message.
Multi-Alphabet Substitution Cipher - Answers Doing something like +1, -2, +3 and shifting each
character a different amount to the left or right. For example, doing +1, -2, +3 with dog would
results in emj.
Cipher Disks - Answers A disk you rotated to encrypt/decrypt. Created by Leon Alberti. Similar
technologies were used in the Enigma machine. Considered the forefather of modern encryption.
Vigenere Cipher - Answers Invented by Giovan Battista Bellaso in middle 1553. Vigenere created
a stronger version of the cipher. Combining/Weaving Caesar cipher. Not cracked until late
1800s. It is a cipher square with A to Z across all the columns and rows. You then use a
keyword to encrypt the message. For example, if the message is cat, and the keyword is horse,
you would look up where c and h intersect on the table (which is j), then where a and o intersect
(o) and t and r (k). Cat would then be encrypted as jok.
Playfair Cipher - Answers Invented by Charles Wheatstone in mid 1800s. Lord Playfair pushed
use of it. Uses a 5x5 table and a key word. Rest of the alphabet is placed on table in alphabetic
order, skipping letters used in the keyword. You break up the message into two character
chunks and return a single character value. If the letters appear on the same row of your table,
replace them with the letters to the right. If it is on the same column, replace them with the
letters below.
ADFGVX Cipher - Answers Invented by Colonel Fritz Nebel in 1918. It is a 6x6 grid with ADFGVX
at the top of each column and beginning of each row. The 26 letters and numbers 0-10 are
placed randomly on the table. You then replace each character of your message with two
characters which are represented by the column followed by the row each character is present
in.
Enigma Machine - Answers Invented between World Wars, used by Germans and Japanese.
Data could be transmitted both via radio or printed on paper. Designed so that when a key was
,pressed, the cipher text for that plain text was different each time. Was a multi-alphabet cipher
with 26 possible alphabets.
Kerckhoff's Principle - Answers We can expose everything but the private key and the data can
still be secure.
Issue with Symmetric Encryption - Answers There's only one key, and it's difficult to only have
both parties who need the key to have it. It typically needs to be sent via another medium than
the message or else it could be compromised by the attacker. Keys can also be sent via out of
band (off the network being used to send the message).
Binary Math - Answers Base 2 system instead of base 10 system.
Binary AND - Answers If both numbers have a one in the same place, then the resultant number
is a one. If not then it is a zero
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary OR - Answers Checks to see if there is a one in either or both numbers in the same place.
If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary XOR (Exclusive OR) ⊕ - Answers Checks to see if there is a one in either number in the
same place. If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
, Result - 1000
XOR is reversible. If you XOR the result with the 2nd number, you will get the 1st number as a
result. If you XOR the result with the 1st number, you will get the 2nd number as a result.
Substitution - Answers XORing the plain text with the key.
Transposition - Answers Swapping blocks of text.
Confusion - Answers Making the relationship between a key and the ciphertext as complex as
possible.
Diffusion - Answers Each binary digit (bit) of the ciphertext should depend on several parts of
the key, obscuring the connections between the two.
Avalanche - Answers The concept that if one bit of data changes, the cipher text will all
completely change as well.
Key Schedule - Answers An algorithm for the key that calculates the subkeys for each round that
the encryption goes through.
Hybrid Encryption - Answers Data is encrypted with a symmetric encryption algorithm, the
symmetric private key is sent to the other party with asymmetric encryption.
Symmetric Algorithms - Answers Examples are DES, 3DES, DESX, AES, Blowfish, Serpent,
Twofish, Skipjack, IDEA
Whitening - Answers A technique used to increase the security of block ciphers. It consists of
steps that combine the data with portions of the key (most commonly using a simple XOR)
before the first round and after the last round of encryption.
Block Cipher - Answers Data fills up a block (typically 64 or 128 bits) and that block is encrypted
as a whole. Slower than stream ciphers. If a block was not full, you would need to pad the data
to end up at the block size.
Feistel Network - Answers Chunk data into evenly sized blocks. The two chunks are typically
called L0 and R0 (left 0 and right 0). As long as these are even, it is considered a
traditional/normal Feistel Cipher. An unbalanced Feistel Cipher is when the basket does not split
evenly. Next is the round function, which is applied to both halves and is used to go through the
multiple rounds/iterations based on the symmetric encryption algorithm. Output of each round
function is XORed with the other half (L0 is XORed with R0). R0 is then moved over to L0. R0 is
moved over to the left and XORed.
DES - Answers Symmetric algorithm. One of the most widely deployed algorithms in the world,
even though it is no longer recommended or considered secure. 64 bit key (56 bits + 8 bits
Atbash Cipher - Answers Invented by the Hebrew. Single substitution monoalphabetic cipher
that substitutes each letter with it's reverse (a and z, b and y, etc).
Caesar Cipher - Answers Monoalphabetic cipher where letters are shifted one or more letters in
either direction.
ROT 13 - Answers Monoalphabetic cipher that shifts characters 13 characters. Stands for
Rotate 13. A would become N, B would become O, etc.
Scytale Cipher - Answers Was a staff with papyrus or letter wrapped around it so edges would
line up. There would be a stream of characters which would show you your message. When
unwound it would be a random string of characters. Would need an identical size staff on other
end for other individuals to decode message.
Multi-Alphabet Substitution Cipher - Answers Doing something like +1, -2, +3 and shifting each
character a different amount to the left or right. For example, doing +1, -2, +3 with dog would
results in emj.
Cipher Disks - Answers A disk you rotated to encrypt/decrypt. Created by Leon Alberti. Similar
technologies were used in the Enigma machine. Considered the forefather of modern encryption.
Vigenere Cipher - Answers Invented by Giovan Battista Bellaso in middle 1553. Vigenere created
a stronger version of the cipher. Combining/Weaving Caesar cipher. Not cracked until late
1800s. It is a cipher square with A to Z across all the columns and rows. You then use a
keyword to encrypt the message. For example, if the message is cat, and the keyword is horse,
you would look up where c and h intersect on the table (which is j), then where a and o intersect
(o) and t and r (k). Cat would then be encrypted as jok.
Playfair Cipher - Answers Invented by Charles Wheatstone in mid 1800s. Lord Playfair pushed
use of it. Uses a 5x5 table and a key word. Rest of the alphabet is placed on table in alphabetic
order, skipping letters used in the keyword. You break up the message into two character
chunks and return a single character value. If the letters appear on the same row of your table,
replace them with the letters to the right. If it is on the same column, replace them with the
letters below.
ADFGVX Cipher - Answers Invented by Colonel Fritz Nebel in 1918. It is a 6x6 grid with ADFGVX
at the top of each column and beginning of each row. The 26 letters and numbers 0-10 are
placed randomly on the table. You then replace each character of your message with two
characters which are represented by the column followed by the row each character is present
in.
Enigma Machine - Answers Invented between World Wars, used by Germans and Japanese.
Data could be transmitted both via radio or printed on paper. Designed so that when a key was
,pressed, the cipher text for that plain text was different each time. Was a multi-alphabet cipher
with 26 possible alphabets.
Kerckhoff's Principle - Answers We can expose everything but the private key and the data can
still be secure.
Issue with Symmetric Encryption - Answers There's only one key, and it's difficult to only have
both parties who need the key to have it. It typically needs to be sent via another medium than
the message or else it could be compromised by the attacker. Keys can also be sent via out of
band (off the network being used to send the message).
Binary Math - Answers Base 2 system instead of base 10 system.
Binary AND - Answers If both numbers have a one in the same place, then the resultant number
is a one. If not then it is a zero
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary OR - Answers Checks to see if there is a one in either or both numbers in the same place.
If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary XOR (Exclusive OR) ⊕ - Answers Checks to see if there is a one in either number in the
same place. If so, the resultant number is one, if not, it is zero.
1st number - 1100
2nd number - 0100
--------------------------
, Result - 1000
XOR is reversible. If you XOR the result with the 2nd number, you will get the 1st number as a
result. If you XOR the result with the 1st number, you will get the 2nd number as a result.
Substitution - Answers XORing the plain text with the key.
Transposition - Answers Swapping blocks of text.
Confusion - Answers Making the relationship between a key and the ciphertext as complex as
possible.
Diffusion - Answers Each binary digit (bit) of the ciphertext should depend on several parts of
the key, obscuring the connections between the two.
Avalanche - Answers The concept that if one bit of data changes, the cipher text will all
completely change as well.
Key Schedule - Answers An algorithm for the key that calculates the subkeys for each round that
the encryption goes through.
Hybrid Encryption - Answers Data is encrypted with a symmetric encryption algorithm, the
symmetric private key is sent to the other party with asymmetric encryption.
Symmetric Algorithms - Answers Examples are DES, 3DES, DESX, AES, Blowfish, Serpent,
Twofish, Skipjack, IDEA
Whitening - Answers A technique used to increase the security of block ciphers. It consists of
steps that combine the data with portions of the key (most commonly using a simple XOR)
before the first round and after the last round of encryption.
Block Cipher - Answers Data fills up a block (typically 64 or 128 bits) and that block is encrypted
as a whole. Slower than stream ciphers. If a block was not full, you would need to pad the data
to end up at the block size.
Feistel Network - Answers Chunk data into evenly sized blocks. The two chunks are typically
called L0 and R0 (left 0 and right 0). As long as these are even, it is considered a
traditional/normal Feistel Cipher. An unbalanced Feistel Cipher is when the basket does not split
evenly. Next is the round function, which is applied to both halves and is used to go through the
multiple rounds/iterations based on the symmetric encryption algorithm. Output of each round
function is XORed with the other half (L0 is XORed with R0). R0 is then moved over to L0. R0 is
moved over to the left and XORed.
DES - Answers Symmetric algorithm. One of the most widely deployed algorithms in the world,
even though it is no longer recommended or considered secure. 64 bit key (56 bits + 8 bits
