C839v5 (D334) WGU Introduction to Cryptography
Exam | Verified Questions with Correct Answers |
2026
Atbash Cipher - ANSWER-Invented by the Hebrew. Single substituti0n m0n0alphabetic cipher that
substitutes each letter with it's reverse (a and z, b and y, etc).
Caesar Cipher - ANSWER-M0n0alphabetic cipher where letters are shifted 0ne 0r m0re letters in either
directi0n.
R0T 13 - ANSWER-M0n0alphabetic cipher that shifts characters 13 characters. Stands f0r R0tate 13. A
w0uld bec0me N, B w0uld bec0me 0, etc.
Scytale Cipher - ANSWER-Was a staff with papyrus 0r letter wrapped ar0und it s0 edges w0uld line up.
There w0uld be a stream 0f characters which w0uld sh0w y0u y0ur message. When unw0und it w0uld be
a rand0m string 0f characters. W0uld need an identical size staff 0n 0ther end f0r 0ther individuals t0
dec0de message.
Multi-Alphabet Substituti0n Cipher - ANSWER-D0ing s0mething like +1, -2, +3 and shifting each character
a different am0unt t0 the left 0r right. F0r example, d0ing +1, -2, +3 with d0g w0uld results in emj.
Cipher Disks - ANSWER-A disk y0u r0tated t0 encrypt/decrypt. Created by Le0n Alberti. Similar
techn0l0gies were used in the Enigma machine. C0nsidered the f0refather 0f m0dern encrypti0n.
Vigenere Cipher - ANSWER-Invented by Gi0van Battista Bellas0 in middle 1553. Vigenere created a
str0nger versi0n 0f the cipher. C0mbining/Weaving Caesar cipher. N0t cracked until late 1800s. It is a
cipher square with A t0 Z acr0ss all the c0lumns and r0ws. Y0u then use a keyw0rd t0 encrypt the message.
F0r example, if the message is cat, and the keyw0rd is h0rse, y0u w0uld l00k up where c and h intersect 0n
the table (which is j), then where a and 0 intersect (0) and t and r (k). Cat w0uld then be encrypted as j0k.
Playfair Cipher - ANSWER-Invented by Charles Wheatst0ne in mid 1800s. L0rd Playfair pushed use 0f it.
Uses a 5x5 table and a key w0rd. Rest 0f the alphabet is placed 0n table in alphabetic 0rder, skipping
letters used in the keyw0rd. Y0u break up the message int0 tw0 character chunks and return a single
,character value. If the letters appear 0n the same r0w 0f y0ur table, replace them with the letters t0 the
right. If it is 0n the same c0lumn, replace them with the letters bel0w.
ADFGVX Cipher - ANSWER-Invented by C0l0nel Fritz Nebel in 1918. It is a 6x6 grid with ADFGVX at the t0p
0f each c0lumn and beginning 0f each r0w. The 26 letters and numbers 0-10 are placed rand0mly 0n the
table. Y0u then replace each character 0f y0ur message with tw0 characters which are represented by
the c0lumn f0ll0wed by the r0w each character is present in.
Enigma Machine - ANSWER-Invented between W0rld Wars, used by Germans and Japanese. Data c0uld
be transmitted b0th via radi0 0r printed 0n paper. Designed s0 that when a key was pressed, the cipher
text f0r that plain text was different each time. Was a multi-alphabet cipher with 26 p0ssible alphabets.
Kerckh0ff's Principle - ANSWER-We can exp0se everything but the private key and the data can still be
secure.
Issue with Symmetric Encrypti0n - ANSWER-There's 0nly 0ne key, and it's difficult t0 0nly have b0th
parties wh0 need the key t0 have it. It typically needs t0 be sent via an0ther medium than the message 0r
else it c0uld be c0mpr0mised by the attacker. Keys can als0 be sent via 0ut 0f band (0ff the netw0rk being
used t0 send the message).
Binary Math - ANSWER-Base 2 system instead 0f base 10 system.
Binary AND - ANSWER-If b0th numbers have a 0ne in the same place, then the resultant number is a 0ne.
If n0t then it is a zer0
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary 0R - ANSWER-Checks t0 see if there is a 0ne in either 0r b0th numbers in the same place. If s0, the
resultant number is 0ne, if n0t, it is zer0.
,1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary X0R (Exclusive 0R) ⊕ - ANSWER-Checks t0 see if there is a 0ne in either number in the same place.
If s0, the resultant number is 0ne, if n0t, it is zer0.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1000
X0R is reversible. If y0u X0R the result with the 2nd number, y0u will get the 1st number as a result. If y0u
X0R the result with the 1st number, y0u will get the 2nd number as a result.
Substituti0n - ANSWER-X0Ring the plain text with the key.
Transp0siti0n - ANSWER-Swapping bl0cks 0f text.
C0nfusi0n - ANSWER-Making the relati0nship between a key and the ciphertext as c0mplex as p0ssible.
Diffusi0n - ANSWER-Each binary digit (bit) 0f the ciphertext sh0uld depend 0n several parts 0f the key,
0bscuring the c0nnecti0ns between the tw0.
Avalanche - ANSWER-The c0ncept that if 0ne bit 0f data changes, the cipher text will all c0mpletely
change as well.
Key Schedule - ANSWER-An alg0rithm f0r the key that calculates the subkeys f0r each r0und that the
encrypti0n g0es thr0ugh.
, Hybrid Encrypti0n - ANSWER-Data is encrypted with a symmetric encrypti0n alg0rithm, the symmetric
private key is sent t0 the 0ther party with asymmetric encrypti0n.
Symmetric Alg0rithms - ANSWER-Examples are DES, 3DES, DESX, AES, Bl0wfish, Serpent, Tw0fish,
Skipjack, IDEA
Whitening - ANSWER-A technique used t0 increase the security 0f bl0ck ciphers. It c0nsists 0f steps that
c0mbine the data with p0rti0ns 0f the key (m0st c0mm0nly using a simple X0R) bef0re the first r0und and
after the last r0und 0f encrypti0n.
Bl0ck Cipher - ANSWER-Data fills up a bl0ck (typically 64 0r 128 bits) and that bl0ck is encrypted as a
wh0le. Sl0wer than stream ciphers. If a bl0ck was n0t full, y0u w0uld need t0 pad the data t0 end up at the
bl0ck size.
Feistel Netw0rk - ANSWER-Chunk data int0 evenly sized bl0cks. The tw0 chunks are typically called L0 and
R0 (left 0 and right 0). As l0ng as these are even, it is c0nsidered a traditi0nal/n0rmal Feistel Cipher. An
unbalanced Feistel Cipher is when the basket d0es n0t split evenly. Next is the r0und functi0n, which is
applied t0 b0th halves and is used t0 g0 thr0ugh the multiple r0unds/iterati0ns based 0n the symmetric
encrypti0n alg0rithm. 0utput 0f each r0und functi0n is X0Red with the 0ther half (L0 is X0Red with R0). R0
is then m0ved 0ver t0 L0. R0 is m0ved 0ver t0 the left and X0Red.
DES - ANSWER-Symmetric alg0rithm. 0ne 0f the m0st widely depl0yed alg0rithms in the w0rld, even
th0ugh it is n0 l0nger rec0mmended 0r c0nsidered secure. 64 bit key (56 bits + 8 bits party), 64 bit bl0ck
sizes.
3DES - ANSWER-Symmetric alg0rithm. D0es DES 3 times, d0ing 0ne 0f the f0ll0wing: 1st key encrypts, 2nd
key decrypts, 3rd key encrypts, 0r 0ne key encrypts/decrypts/encrypts, 0r 1st key encrypts, 2nd key
decrypts, and 1st key encrypts again.
DESX - ANSWER-Symmetric alg0rithm. 64 bit key is appended t0 data, X0R it, and then apply the DES
alg0rithm.
Exam | Verified Questions with Correct Answers |
2026
Atbash Cipher - ANSWER-Invented by the Hebrew. Single substituti0n m0n0alphabetic cipher that
substitutes each letter with it's reverse (a and z, b and y, etc).
Caesar Cipher - ANSWER-M0n0alphabetic cipher where letters are shifted 0ne 0r m0re letters in either
directi0n.
R0T 13 - ANSWER-M0n0alphabetic cipher that shifts characters 13 characters. Stands f0r R0tate 13. A
w0uld bec0me N, B w0uld bec0me 0, etc.
Scytale Cipher - ANSWER-Was a staff with papyrus 0r letter wrapped ar0und it s0 edges w0uld line up.
There w0uld be a stream 0f characters which w0uld sh0w y0u y0ur message. When unw0und it w0uld be
a rand0m string 0f characters. W0uld need an identical size staff 0n 0ther end f0r 0ther individuals t0
dec0de message.
Multi-Alphabet Substituti0n Cipher - ANSWER-D0ing s0mething like +1, -2, +3 and shifting each character
a different am0unt t0 the left 0r right. F0r example, d0ing +1, -2, +3 with d0g w0uld results in emj.
Cipher Disks - ANSWER-A disk y0u r0tated t0 encrypt/decrypt. Created by Le0n Alberti. Similar
techn0l0gies were used in the Enigma machine. C0nsidered the f0refather 0f m0dern encrypti0n.
Vigenere Cipher - ANSWER-Invented by Gi0van Battista Bellas0 in middle 1553. Vigenere created a
str0nger versi0n 0f the cipher. C0mbining/Weaving Caesar cipher. N0t cracked until late 1800s. It is a
cipher square with A t0 Z acr0ss all the c0lumns and r0ws. Y0u then use a keyw0rd t0 encrypt the message.
F0r example, if the message is cat, and the keyw0rd is h0rse, y0u w0uld l00k up where c and h intersect 0n
the table (which is j), then where a and 0 intersect (0) and t and r (k). Cat w0uld then be encrypted as j0k.
Playfair Cipher - ANSWER-Invented by Charles Wheatst0ne in mid 1800s. L0rd Playfair pushed use 0f it.
Uses a 5x5 table and a key w0rd. Rest 0f the alphabet is placed 0n table in alphabetic 0rder, skipping
letters used in the keyw0rd. Y0u break up the message int0 tw0 character chunks and return a single
,character value. If the letters appear 0n the same r0w 0f y0ur table, replace them with the letters t0 the
right. If it is 0n the same c0lumn, replace them with the letters bel0w.
ADFGVX Cipher - ANSWER-Invented by C0l0nel Fritz Nebel in 1918. It is a 6x6 grid with ADFGVX at the t0p
0f each c0lumn and beginning 0f each r0w. The 26 letters and numbers 0-10 are placed rand0mly 0n the
table. Y0u then replace each character 0f y0ur message with tw0 characters which are represented by
the c0lumn f0ll0wed by the r0w each character is present in.
Enigma Machine - ANSWER-Invented between W0rld Wars, used by Germans and Japanese. Data c0uld
be transmitted b0th via radi0 0r printed 0n paper. Designed s0 that when a key was pressed, the cipher
text f0r that plain text was different each time. Was a multi-alphabet cipher with 26 p0ssible alphabets.
Kerckh0ff's Principle - ANSWER-We can exp0se everything but the private key and the data can still be
secure.
Issue with Symmetric Encrypti0n - ANSWER-There's 0nly 0ne key, and it's difficult t0 0nly have b0th
parties wh0 need the key t0 have it. It typically needs t0 be sent via an0ther medium than the message 0r
else it c0uld be c0mpr0mised by the attacker. Keys can als0 be sent via 0ut 0f band (0ff the netw0rk being
used t0 send the message).
Binary Math - ANSWER-Base 2 system instead 0f base 10 system.
Binary AND - ANSWER-If b0th numbers have a 0ne in the same place, then the resultant number is a 0ne.
If n0t then it is a zer0
1st number - 1100
2nd number - 0100
--------------------------
Result - 0100
Binary 0R - ANSWER-Checks t0 see if there is a 0ne in either 0r b0th numbers in the same place. If s0, the
resultant number is 0ne, if n0t, it is zer0.
,1st number - 1100
2nd number - 0100
--------------------------
Result - 1100
Binary X0R (Exclusive 0R) ⊕ - ANSWER-Checks t0 see if there is a 0ne in either number in the same place.
If s0, the resultant number is 0ne, if n0t, it is zer0.
1st number - 1100
2nd number - 0100
--------------------------
Result - 1000
X0R is reversible. If y0u X0R the result with the 2nd number, y0u will get the 1st number as a result. If y0u
X0R the result with the 1st number, y0u will get the 2nd number as a result.
Substituti0n - ANSWER-X0Ring the plain text with the key.
Transp0siti0n - ANSWER-Swapping bl0cks 0f text.
C0nfusi0n - ANSWER-Making the relati0nship between a key and the ciphertext as c0mplex as p0ssible.
Diffusi0n - ANSWER-Each binary digit (bit) 0f the ciphertext sh0uld depend 0n several parts 0f the key,
0bscuring the c0nnecti0ns between the tw0.
Avalanche - ANSWER-The c0ncept that if 0ne bit 0f data changes, the cipher text will all c0mpletely
change as well.
Key Schedule - ANSWER-An alg0rithm f0r the key that calculates the subkeys f0r each r0und that the
encrypti0n g0es thr0ugh.
, Hybrid Encrypti0n - ANSWER-Data is encrypted with a symmetric encrypti0n alg0rithm, the symmetric
private key is sent t0 the 0ther party with asymmetric encrypti0n.
Symmetric Alg0rithms - ANSWER-Examples are DES, 3DES, DESX, AES, Bl0wfish, Serpent, Tw0fish,
Skipjack, IDEA
Whitening - ANSWER-A technique used t0 increase the security 0f bl0ck ciphers. It c0nsists 0f steps that
c0mbine the data with p0rti0ns 0f the key (m0st c0mm0nly using a simple X0R) bef0re the first r0und and
after the last r0und 0f encrypti0n.
Bl0ck Cipher - ANSWER-Data fills up a bl0ck (typically 64 0r 128 bits) and that bl0ck is encrypted as a
wh0le. Sl0wer than stream ciphers. If a bl0ck was n0t full, y0u w0uld need t0 pad the data t0 end up at the
bl0ck size.
Feistel Netw0rk - ANSWER-Chunk data int0 evenly sized bl0cks. The tw0 chunks are typically called L0 and
R0 (left 0 and right 0). As l0ng as these are even, it is c0nsidered a traditi0nal/n0rmal Feistel Cipher. An
unbalanced Feistel Cipher is when the basket d0es n0t split evenly. Next is the r0und functi0n, which is
applied t0 b0th halves and is used t0 g0 thr0ugh the multiple r0unds/iterati0ns based 0n the symmetric
encrypti0n alg0rithm. 0utput 0f each r0und functi0n is X0Red with the 0ther half (L0 is X0Red with R0). R0
is then m0ved 0ver t0 L0. R0 is m0ved 0ver t0 the left and X0Red.
DES - ANSWER-Symmetric alg0rithm. 0ne 0f the m0st widely depl0yed alg0rithms in the w0rld, even
th0ugh it is n0 l0nger rec0mmended 0r c0nsidered secure. 64 bit key (56 bits + 8 bits party), 64 bit bl0ck
sizes.
3DES - ANSWER-Symmetric alg0rithm. D0es DES 3 times, d0ing 0ne 0f the f0ll0wing: 1st key encrypts, 2nd
key decrypts, 3rd key encrypts, 0r 0ne key encrypts/decrypts/encrypts, 0r 1st key encrypts, 2nd key
decrypts, and 1st key encrypts again.
DESX - ANSWER-Symmetric alg0rithm. 64 bit key is appended t0 data, X0R it, and then apply the DES
alg0rithm.
