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INTRODUCTION TO CRYPTOGRAPHY - D334
QUESTIONS AND ANSWERS 2025
XOR the following
0101110101010111
1001100000111010
------------------ - .....ANSWER .....
✔✔1100010101101101
asymmetric key-based encryption
-typical methods - .....ANSWER ..... ✔✔RSA
DSA
El Gamal
Symmetric key-based encryption
-Typical Methods - .....ANSWER ..... ✔✔RC2- 40 bit
key size 64 bit block
RC4- (Stream Cipher)- Used in SSL and WEP
RC5- (Variable Key size, 32, 64, or 128 bit block size)
AES- (128, 192 or 256 bit key size, 128 bit block size)
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DES- (56 bit key size. 64 bit Block size)
3DES- (112 bit key size, 64 bit block size)
Block Encryption - .....ANSWER ..... ✔✔RC2(40 bit key
size)
RC5(Variable block size)
IDEA
DES
3DES
AES (Rijndael)
Blowfish
twofish
stream encryption - .....ANSWER ..... ✔✔RC4
Chacha
Rainbow Attack - .....ANSWER ..... ✔✔The method of
knowing the mapping between the hashed values and
the original data
Dictionary-type attack - .....ANSWER ..... ✔✔a brute
force analysis
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∉ - .....ANSWER ..... ✔✔does not belong to
when an object is not in a set
∈ - .....ANSWER ..... ✔✔Belongs to
when an object is within a set
⊆ - .....ANSWER ..... ✔✔subset
subset has fewer elements or equal to the set
A ∪ B - .....ANSWER ..... ✔✔union (objects that
belong to set A or set B)
| - .....ANSWER ..... ✔✔such that
A ∩ B - .....ANSWER ..... ✔✔Intersection: in both A
and B
Enigma Machine -Cypher 10 - .....ANSWER .....
✔✔Used a polyalphabetic substitution cipher, which
did not repeat within a reasonable time period, along
with a secret key. For the cracking of the Enigma cipher,
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the challenge was thus to determine both the algorithm
used and the key. Enigma's main weakness, though, was
that none of the plain text letters could be ciphered as
itself.
Four-square cipher9 - .....ANSWER ..... ✔✔Uses four
5 × 5 matrices arranged in a square, are where each
matrix contains 25 letters for encoding and decoding
operations.
One-time pad cypher8 - .....ANSWER ..... ✔✔Cypher
Code mapping that is only used once.
Advantage: it is essentially unbreakable.
Disadvantage: it takes lots of work as you would have
to generate the pad to be used, each time.
Vigenere Cipher 7 - .....ANSWER .....
✔✔Polyalphabetic cipher that involves using a
different mapping, based on a keyword, for each
character of the cipher. An advantage of this type of
cipher is that the same plaintext character is likely to be
coded to different mappings, depending on the position
of the keyword, making guessing more difficult.
INTRODUCTION TO CRYPTOGRAPHY - D334
QUESTIONS AND ANSWERS 2025
XOR the following
0101110101010111
1001100000111010
------------------ - .....ANSWER .....
✔✔1100010101101101
asymmetric key-based encryption
-typical methods - .....ANSWER ..... ✔✔RSA
DSA
El Gamal
Symmetric key-based encryption
-Typical Methods - .....ANSWER ..... ✔✔RC2- 40 bit
key size 64 bit block
RC4- (Stream Cipher)- Used in SSL and WEP
RC5- (Variable Key size, 32, 64, or 128 bit block size)
AES- (128, 192 or 256 bit key size, 128 bit block size)
,2|Page
DES- (56 bit key size. 64 bit Block size)
3DES- (112 bit key size, 64 bit block size)
Block Encryption - .....ANSWER ..... ✔✔RC2(40 bit key
size)
RC5(Variable block size)
IDEA
DES
3DES
AES (Rijndael)
Blowfish
twofish
stream encryption - .....ANSWER ..... ✔✔RC4
Chacha
Rainbow Attack - .....ANSWER ..... ✔✔The method of
knowing the mapping between the hashed values and
the original data
Dictionary-type attack - .....ANSWER ..... ✔✔a brute
force analysis
,3|Page
∉ - .....ANSWER ..... ✔✔does not belong to
when an object is not in a set
∈ - .....ANSWER ..... ✔✔Belongs to
when an object is within a set
⊆ - .....ANSWER ..... ✔✔subset
subset has fewer elements or equal to the set
A ∪ B - .....ANSWER ..... ✔✔union (objects that
belong to set A or set B)
| - .....ANSWER ..... ✔✔such that
A ∩ B - .....ANSWER ..... ✔✔Intersection: in both A
and B
Enigma Machine -Cypher 10 - .....ANSWER .....
✔✔Used a polyalphabetic substitution cipher, which
did not repeat within a reasonable time period, along
with a secret key. For the cracking of the Enigma cipher,
, 4|Page
the challenge was thus to determine both the algorithm
used and the key. Enigma's main weakness, though, was
that none of the plain text letters could be ciphered as
itself.
Four-square cipher9 - .....ANSWER ..... ✔✔Uses four
5 × 5 matrices arranged in a square, are where each
matrix contains 25 letters for encoding and decoding
operations.
One-time pad cypher8 - .....ANSWER ..... ✔✔Cypher
Code mapping that is only used once.
Advantage: it is essentially unbreakable.
Disadvantage: it takes lots of work as you would have
to generate the pad to be used, each time.
Vigenere Cipher 7 - .....ANSWER .....
✔✔Polyalphabetic cipher that involves using a
different mapping, based on a keyword, for each
character of the cipher. An advantage of this type of
cipher is that the same plaintext character is likely to be
coded to different mappings, depending on the position
of the keyword, making guessing more difficult.
